OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 22 — Oct. 24, 2011
  • pp: 21768–21785
« Show journal navigation

Influence of various growth conditions on Fresnel diffraction patterns of bacteria colonies examined in the optical system with converging spherical wave illumination

Igor Buzalewicz, Alina Wieliczko, and Halina Podbielska  »View Author Affiliations


Optics Express, Vol. 19, Issue 22, pp. 21768-21785 (2011)
http://dx.doi.org/10.1364/OE.19.021768


View Full Text Article

Acrobat PDF (1824 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

The novel optical system based on converging spherical wave illumination for analysis of bacteria colonies diffraction patterns, is proposed. The complex physical model of light transformation on bacteria colonies in this system, is presented. Fresnel diffraction patterns of bacteria colonies Escherichia coli, Salmonella enteritidis, Staphylococcus aureus grown in various conditions, were examined. It was demonstrated that the proposed system enables the characterization of morphological changes of colony structures basing on the changes of theirs Fresnel diffraction patterns.

© 2011 OSA

1. Introduction

One of the most important issues in many fields of life science, health safety and food production is the microbial contamination. The rapid, accurate and effective detection of pathogens is recently widely studied by many groups, also due to possible biohazard [1

1. K. Christen, “Bioterrorism and waterborne pathogens: how big is the threat?” Environ. Sci. Technol. 35(19), 396A–397A (2001). [CrossRef] [PubMed]

, 2

2. A. M. Nicol, Ch. Hurrell, W. McDowall, K. Bartlett, and N. Elmieh, “Communicating the risks of a new, emerging pathogen: the case of Cryptococcus gattii,” Risk Anal. 28(2), 373–386 (2008). [CrossRef] [PubMed]

]. Although the majority of microorganisms are able to coexist with humans, plants and animals with beneficial relations, many of them are responsible for various infectious diseases or may cause the contamination of food products. The increasing number of bacterial species identified as important food- and waterborne pathogens, is observed continuously. The big hazard are new laboratory-created pathogens [3

3. C. Dennis, “The bugs of war,” Nature 411(6835), 232–235 (2001). [CrossRef] [PubMed]

, 4

4. T. Ersek and Z. Nagy, “Species hybrids in the genus Phytophthora with emphasis on the alder pathogen Phytophthora alni: a review,” Eur. J. Plant Pathol. 22(1), 31–39 (2010).

] and increased bacteria resistance to commonly used antibacterial agents (antibiotics, sterilization chemicals etc.). Especially, antibiotics resistance is frequently discussed in the medical literature [5

5. S. B. Levy and B. Marshall, “Antibacterial resistance worldwide: causes, challenges and responses,” Nat. Med. 10(12Suppl), S122–S129 (2004). [CrossRef] [PubMed]

7

7. A. S. Colsky, R. S. Kirsner, and F. A. Kerdel, “Analysis of antibiotic susceptibilities of skin wound flora in hospitalized dermatology patients. The crisis of antibiotic resistance has come to the surface,” Arch. Dermatol. 134(8), 1006–1009 (1998). [CrossRef] [PubMed]

]. The National Institute of Allergy and Infectious Diseases - NIAID warns that over 70% of various bacteria species, most often causing hospital infections, are already completely resistant to at least one kind of antibiotics commonly used for their treatment [8]. By these reasons the new modalities to detect and combat pathogenic microbes are in focus of many international and national initiatives.

Experiments previously performed in our group have shown that analysis of bacteria colonies Fourier spectra, considered in general as diffraction patterns, can be used to estimate the bacteria colonies number and in consequence, to asses antimicrobial properties of different antimicrobial agents [43

43. I. Buzalewicz, K. Wysocka, and H. Podbielska, “Exploiting of optical transforms for bacteria evaluation in vitro,” Proc. SPIE 7371, 73711H, 73711H-6 (2009). [CrossRef]

45

45. I. Buzalewicz, K. Wysocka–Król, K. Kowal, and H. Podbielska, “Evaluation of antibacterial agents efficiency,” in Information Technologies in Biomedicine 2, E. Pietka, J. Kawa ed. (Springer-Verlag, 2010).

].

Here, a new approach towards examination of forward light scattering on bacteria colonies in a Fourier transform optical system with converging spherical wave, will be presented. According to our knowledge, this is a first attempt to exploit such a system for analyzing the bacteria colony diffraction signature, as well as to examine its Fresnel patterns. This new diffraction-based sensor offers more effective analysis of scatterograms. The proposed system possess some useful features as the possibility of diffraction patterns scaling and compression of the observation plane in the same setup. This solution offers also low level of optical aberrations. These factors can significantly improve the analysis of diffraction patterns of bacteria colonies. The complex physical model of light transformation on bacteria colonies grown on solid nutrient medium in Petri dish, will be presented. The influence of various growth conditions (temperature of incubation, time of incubation, kind of nutrient medium) on the Fresnel diffraction patterns, will be examined. Obtained results have demonstrated that there is a high correlation between the morphological structure of the colony and recorded diffraction patterns.

2. The physical model of light transformation on bacteria colonies in the optical system with converging spherical wave illumination

2.1 The wave field transformation

For simplicity, let assume that a coherent plane wave Uin.(x0,y0) = A with the amplitude A, propagating along optical axis z perpendicularly to the (x0,y0) plane, falls on the transforming lens L0. It means that the point light source is located in an infinite distance from the transforming lens (see Fig. 1
Fig. 1 Proposed optical system configuration for characterization of bacteria colonies diffraction patterns: L0 transforming lens in (x0,y0) plane, bacteria colonies on Petri dish in (x1,y1) plane, observation plane (x2,y2).
). The lens L0 with the focal distance f is transforming the incident plane wave into the converging spherical wave, which can be described as [46

46. J. W. Goodman, Introduction to Fourier Optics, 3rd ed. (Robert & Company Publishers, 2005).

]
Uout.(x0,y0)=AP(x0,y0)exp{iπλf(x02+y02)}=AP(x0,y0)ψ(x0,y0;F),
(1)
where λ is the wavelength of incident wave, F=1/f, P(x0,y0) is a pupil function of the transforming lens and the function ψ(x,y,p) represents Gaussian function:

ψ(x,y,p)=exp{iπpλ(x2+y2)}.
(2)

Between the lens L0 and the object plane (x1,y1) located in the distance z1 from the lens, the free propagation takes place, therefore the optical field can be described using the Fresnel diffraction approximation, as follows:
U(xm+1,ym+1)=exp(ikzm+1)iλzm+1×++U(xm,ym)exp{iπλzm+1[(xm+1xm)2+(ym+1ym)2]}dxmdym=,=C(λ,Zm+1)++U(xm,ym)ψ(xm+1xm,ym+1ym,Zm+1)dxmdym
(3)
where-Zm+1=1/zm+1.

Finally, the wave field illuminating the object plane can be expressed as:
Uin.(x1,y1)=C(λ,Z1)++Uout.(x0,y0)ψ(x1x0,y1y0,Z1)dx0dy0,
(4)
where C(λ, Z1) is a constant characteristic for Fresnel approximation depending on the λ and Z1. Additionally, it was assumed that the finite object is totally illuminated by the converging spherical wave, therefore the pupil function can be ignored. By the substitution of the optical field Uout.(x0,y0) expressed by Eq. (1) to Eq. (4) and taking into account the properties of Gaussian function:
ψ(x1x0,y1y0,Z1)=ψ(x0,y0,Z1)ψ(x1,y1,Z1)exp{i2πλZ1(x0x1+y0y1)},
(5)
and
ψ(x0,y0,Z1)ψ(x0,y0,F)=ψ(x0,y0,Z1F),
(6)
it is possible to transform the Eq. (4) to the following form

Uin.(x1,y1)=C(λ,Z1)Aψ(x1,y1,Z1)++ψ(x0,y0,Z1F)exp{i2πλZ1(x0x1+y0y1)}dx0dy0.
(7)

Moreover, the Fourier transform of Gaussian function can be described by the following formula:
{exp{πc(x2+y2)}}=1cexp{πc(fx2+fy2)},
(8)
where fx, fy are the spatial frequencies and {...} denotes the two-dimensional Fourier transform. So finally, after simple transformations, the optical field Uin.(x0,y0) described by Eq. (7) can be now expressed, as follows:
Uin.(x1,y1)=iλAZ1FC(λ,Z1)ψ(x1,y1,Z1FZ1F),
(9)
or after simple transformation, as:
Uin.(x1,y1)=(ffz1A)exp{ikz1}ψ(x1,y1,Z1FZ1F),
(10)
The Eq. (10) represents a spherical wave converging towards the plane z = f and which amplitude changes proportionally to the ratio f/(f-z1), what is in agreement with geometrical optics predictions [46

46. J. W. Goodman, Introduction to Fourier Optics, 3rd ed. (Robert & Company Publishers, 2005).

,47

47. J. D. Gaskill, Linear Systems, Fourier Transform and Optics, (John Wiley & Sons, 1978).

].

When this wave illuminates the single bacteria colony on Petri dish placed in the object plane (x1,y1), its amplitude and phase are modulated by analyzed object. The contribution of the nutrient medium is limited to the presence of exponential phase shift along optical axis, as well as to the attenuation of a primary amplitude of the incident wave. For simplicity at this stage of analysis, let assume that amplitude transmittance tb(x1,y1) of the bacteria colony is described by the following expression:
tb(x1,y1)=tb0(x1,y1)exp{iϕ(x1,y1)},
(11)
where tB0(x1,y1) expresses the two-dimensional transmission coefficient and φ(x1,y1) is the two-dimensional phase distribution [46

46. J. W. Goodman, Introduction to Fourier Optics, 3rd ed. (Robert & Company Publishers, 2005).

]. The amplitude and phase transformations on bacteria colony of the wave field Uin.(x0,y0), can be simply presented by
U(x1,y1)=Uin.(x1,y1)tb(x1,y1)
(12)
Similarly, as in the case of the free propagation of the optical field from the lens L0 to the object plane, we are using the Fresnel approximation to obtain scattered wave field in the observation plane:
Uin.(x2,y2)=C2(λ,Z2)++U(x1,y1)ψ(x2x1,y2y1,Z2)dx1dy2.
(13)
After rearrangement of Eq. (13) and appropriate substitutions according to the Gaussian function properties as described by Eq. (5), Eq. (6) and Eq. (8), the wave field in the observation plane takes a form:
Uin.(x2,y2)=C(λ,Z1,Z2)(fAfz1)ψ(x2,y2,Z2){tb(x1,y1)ψ(x1,y1,Z˜)}fx=x2Z2λ;fy=y2Z2λ
(14)
where
Z˜=Z2Z1FZ1F
(15)
It can be seen that for Z˜>0 Eq. (14) is describing the Fresnel transform of the bacteria colony amplitude transmittance. However, it should be pointed out that there exist some important differences between this expression and the conventional Fresnel diffraction formula known from scalar theory of diffraction. Presented above expression should be considered as a Fresnel diffraction formula for tb(x1,y1) alone, and not for entire scattered wave field U.(x1,y1), as it is commonly regarded. Moreover, the parameter Z˜ is not describing the distance to the observation plane, but rather the nature of diffraction pattern (Fresnel or Fraunhofer), which is observed.

If the observation plane will be shifted to the back focal plane of the transforming lens, then z1 + z2 = f and according to the Eq. (15), the parameter Z˜=0. As a result, the exponential quadratic phase term ψ(x1,y1,Z˜)=1 and the Eq. (14) takes a form of the Fourier transform of the bacteria colony amplitude transmittance alone, which represents the Fraunhofer diffraction formula:
Uin.(x2,y2)=C(λ,Z1,Z2)(fAfz1)ψ(x2,y2,Z2){tb(x1,y1)}fx=x2Z^λ;fy=y2Z^λ,
(16)
where
Z^=1z^=1fz1=Z1FZ1F
(17)
It can be seen that the converging spherical wave illumination eliminates the need for large observation distances for recording the Fraunhofer pattern. In [47

47. J. D. Gaskill, Linear Systems, Fourier Transform and Optics, (John Wiley & Sons, 1978).

] the extended analysis of the converging spherical wave illumination system properties is presented and it was shown that this system allows to compress and distort the observation space along optical axis into the finite region of the space between the diffracting object and the Fourier transform plane. If the location of the observation plane ranges from the object plane z = z1 to the Fourier transform plane z = f, then, it is possible to observe the Fresnel diffraction pattern of the object, which scale depends directly on the value of parameter Z˜ and indirectly on the relation between the distance z1 and f. If the observation plane is near the Fourier transform plane, then Z˜=0 and the Fraunhofer diffraction pattern of the object can be observed with the scaling factor of Z^ depending on the distance z^=fz1. It means that by increasing the distance z^, the size of the diffraction pattern is larger until the object is directly behind the lens. If the distance z^ decreases, the size of the pattern is getting smaller. Moreover, when the point light source is moved closer to the front focal plane of the transforming lens, then the illuminating beam will converge less rapidly and the Fourier transform plane will be moved further from the lens. Therefore, the scale changes of the observed diffraction patterns will be larger. In such optical system the matrix size of used detectors may be smaller due to the possibility of adjusting an appropriate scale of the observed diffraction pattern.

Additionally, to the presented above properties of Fourier transform, the optical system with converging spherical wave illumination possess more advantages comparing to the other Fourier transform systems [48

48. D. Joyeux and S. Lowenthal, “Optical Fourier transform: what is the optimal setup?” Appl. Opt. 21(23), 4368–4372 (1982). [CrossRef] [PubMed]

]. The transforming lens, which is placed in front of the object, must be corrected only for a pair of on-axis points to produce the spherical wave and not for all aberrations for the infinity – focal plane points pairs as in configuration with the plane wave illumination. Therefore, the setup with converging spherical wave illumination is more simple, so the level of coherence noises on optical elements is reduced. Moreover, choosing the same size of the lens as the size of the object allows to avoid the bandwidth limitation of the lens. These properties additionally lower the costs of the system construction.

2.2 The degeneration of Fraunhofer diffraction condition by phase modulation of bacteria colony

Presented above analysis did not take into consideration the phase modulation of the incoming wave field caused by the form of bacteria colony. In general, many bacteria colonies have spheroid shapes, therefore it will affect the validity of the above presented consideration, because no assumption about the object form was made there. In the literature various approaches to the bacteria colonies profile shape are presented: a convex shape [36

36. E. Bae, P. P. Banada, K. Huff, A. K. Bhunia, J. P. Robinson, and E. D. Hirleman, “Biophysical modeling of forward scattering from bacterial colonies using scalar diffraction theory,” Appl. Opt. 46(17), 3639–3648 (2007). [CrossRef] [PubMed]

], a thin film with decreasing tailing edge [49

49. M. A. Bees, P. Andresén, E. Mosekilde, and M. Givskov, “The interaction of thin-film flow, bacterial swarming and cell differentiation in colonies of Serratia liquefaciens,” J. Math. Biol. 40(1), 27–63 (2000). [CrossRef] [PubMed]

] or a Gaussian profile [41

41. E. Bae, N. Bai, A. Aroonnual, J. P. Robinson, A. K. Bhunia, and E. D. Hirleman, “Modeling light propagation through bacterial colonies and its correlation with forward scattering patterns,” J. Biomed. Opt. 15(4), 045001 (2010). [CrossRef] [PubMed]

]. In our approach a convex shape with the single radius of curvature rb (see Fig. 2
Fig. 2 Model of the convex shaped bacteria colony.
), will be analyzed. The total phase delay of the wave field passing through the bacteria colony may be expressed [46

46. J. W. Goodman, Introduction to Fourier Optics, 3rd ed. (Robert & Company Publishers, 2005).

], as
ϕ(x1,y1)=k[ToΔ(x1,y1)nbΔ(x1,y1)],
(18)
where nb is the refractive index of the bacteria colony, T0 is the thickness along optical axis and Δ(x1,y1) is the bacteria colony thickness function in the off-axis region.

Referring to the assumed geometry of the bacteria colony profile, the thickness Δ(x1,y1) can be written as
Δ(x1,y1)=T0zb=T0(rbrb2x12y12)=T0rb(11x12+y12rb2).
(19)
If we expand the square root term in power series and simplify it, the thickness function can be described as
Δ(x1,y1)=T0x12+y122(1r1rb)
(20)
and the phase delay as
ϕ(x1,y1)=knbT0k(nb1)x12+y122(1r1rb)=knT0k(nb1)x12+y122R,
(21)
where R=(n1)(r1rb1). It should be pointed that an additional phase delay along optical axis of a wave passing through the Petri dish and nutrient medium, occurs. Therefore, the refractive indices of the Pethri dish np and the nutrient medium na, as well as their thicknesses Tp and Ta, respectively, should be taken into account, as well. By the substitution of the Eq. (21) to Eq. (11) and further to the diffraction formula represented by Eq. (14), the following expression is obtained:
Uin.(x2,y2)=C˜×{tb0(x1,y1)ψ(x1,y1,Z˜)}fx=x2Z2λ;fy=y2Z2λ,
(22)
where
Z˜=Z2Z1FZ1FR,
(23)
and the constant C˜can be expressed as:
C˜=(fAfz1)exp(ikZ11)exp(ikZ21)ψ(x2,y2,Z2)exp(iknpTp)exp(iknaTa)exp(iknbT0)iλZ21.
(24)
Additional term R in the Eq. (23) indicates that the phase modulation of bacteria colony due to its convex shape and the refractive index nb, affects the conditions of Fraunhofer diffraction observation. Now, the location of the Fourier plane is shifted along the optical axis, respectively to the value of R. Moreover, this parameter affects as well the lateral scale changes of Fresnel pattern, which are correlated with the Z˜. Therefore, it can be seen that for analysis of Fraunhofer patterns the additional information about bacteria colony profile is required.

3. Materials and methods

3.1 Preparation of bacteria samples

3.2 The absorption properties of used nutrient media and selection of the light source

Examined bacteria colonies were grown on solid nutrient media that contain various nutrients for bacteria breeding. The variety of the nutrient media chemical composition can significantly affects their transmission properties. Particularly, it is important to choose an appropriate wavelength of light source. Therefore, the absorption properties of some mostly used nutrient media (MacConkey, agar and Columbia agar) were measured by means of the AvaSpec-3648 spectrometer in the spectral range 300-800 nm with the resolution 2 nm (see Fig. 3
Fig. 3 The absorption spectra of: (a) Columbia agar, (b) Nutrient agar,(c) MacConkey medium.
). It can be seen that generally nutrient media exhibit significant absorption in the UV-A and UV-VIS spectral range. Columbia and nutrient agar have absorbance maximum at ca. 400 nm. However, side lobes in VIS spectral range: 400-600 nm, are observed, as well. In the case of the MacConkey medium the strong absorbance occurs at 330 nm, as well as in the spectral range 400-600 nm. It can be seen that each nutrient medium at wavelengths longer than 600 nm, has lower absorbance. Therefore, as a light source the laser diode module (1mW, collimated beam, Thorlabs) with wavelength 635 nm was chosen for proposed diffraction experiments.

3.3 The optical system configuration and calibration

The schema of the proposed optical system with converging spherical wave illumination is shown on Fig. 4
Fig. 4 The schematic configuration of proposed optical system (explanation in text).
. It includes the laser diode module (635 nm, 1 mW, collimated Thorlabs), beam expander BE (Edmund Optics), transforming lens L (achromatic doublet, focal distance: 48.6 cm, clear aperture: 6.35cm, Edmund Optics), CMOS camera C (EO-1312, Edmund Optics) and XYZ sample positioning stage with Petri dish S, which enables the adjustment of uniform illumination of the single bacteria colony. By changing the position of sample holder along optical axis the diffraction patterns scale can be changed.

Calibration of the system can be accomplished simply by analysis of the diffraction patterns of the exit pupil of the system. Without the object, when such a system is properly focused, so in another words, the detector is located exactly in the back focal plane of the transforming lens, then in the observation plane the Fraunhofer diffraction pattern of the exit pupil can be observed. These exemplary diffraction pattern are showing that optical system with converging spherical wave illumination can compress the observation space and both Fresnel and Fraunhofer patterns can be observed. The Fresnel diffraction pattern of the exit pupil indicates that this system is defocused and the observation plane is in the Fresnel region (see Fig. 5
Fig. 5 Different diffraction patterns of the exit pupil of the optical system: (a) z2=2 cm, (b) z2=9 cm,(c) z2=15 cm Fresnel patterns for increasing distance from the transforming lens, (d) z2=28.8 cm Fraunhofer pattern in the back focal plane of the transforming lens (aperture diameter: 2 mm).
). By changing the position of the camera along the optical axis for fixed position of the object, the various diffraction patterns can be observed: from Fresnel pattern to Fraunhofer pattern. If the converging spherical wave illumination is applied, the lateral dimension of the diffraction pattern decreases with the increasing of the distance between the object and the transforming lens.

4. Results

4.1 Scaling Fresnel patterns of the bacteria colony

The main advantage of the proposed optical system with converging spherical wave illumination has the ability to control the diffraction patterns dimension by changing the sample location along the optical axis, respectively to the fixed positions of the transforming lens and camera.

In order to demonstrate it, Salmonella enteritidis and Staphylococcus aureus colonies on Tryptone soya agar were analyzed. The Fresnel diffraction patterns of single bacteria colony for various object’s positions, were recorded. Exemplary results are shown on Fig. 6
Fig. 6 The change of the dimension of Fresnel diffraction patterns in the case of Salmonella enteritidis colony with decreasing the distance z1:(a) 28 cm, (b) 26.5 cm, (c) 25.3 cm, (d) 24.5cm (bacteria colony diameter: approx. 0.8 mm, beam diameter: approx. 1 mm).
and Fig. 7
Fig. 7 The change of the of Fresnel diffraction patterns of Staphylococcus aureus colony with decreasing the distance z1.: (a) 28 cm, (b) 27cm (bacteria colony diameter: 2.1 mm, beam diameter: approx. 2.1 mm).
. If moving the object towards the transforming lens the pattern becomes larger and on the other hand, it becomes smaller if moving it away from the lens

4.2 Correlation between bacteria colony structure changes and observed Fresnel patterns

It is obvious that the chemical composition of nutrient media has an effect on the bacteria metabolism. The shape of bacteria colony depends, among others, also on bacteria metabolic processes. The shape, size, structure and color of the bacteria colony is widely analyzed in the microbiological diagnosis. These properties depend not only on the bacteria species, but also on various environmental factors such as growth conditions: kind of nutrient medium, temperature, growth media surface wettability etc. Therefore, these parameters should be taken under careful consideration in the procedure of bacteria species identification. In our experiments, Escherichia coli (0119) colonies grown on two different nutrient media (Columbia agar and Tryptone soya agar), were analyzed.

Generally, Fresnel diffraction patterns of Escherichia coli colonies contain the central maximum inside the shadow of colony (bacteria colony shadow is indicated by red arrow), and second one outside this region, with radial spoke-likes intensity maxima. For bacteria colonies grown at 37°C, this second maximum has radial symmetry, but for colonies grown at 15°C this symmetry is broken, however, the general structure of Fresnel patterns is preserved. Therefore, it can be seen that Fresnel patterns are indeed sensitive for morphological changes of bacteria colony structure caused by growth conditions. To analyze more carefully this process, the microscopic images of bacteria colonies structure after low temperature stress at 0°C were recorded with using the spectral filter for 635 nm. The diffraction image of analyzed Escherichia coli (0119) (see Fig. 9(a)
Fig. 9 (a) Shadowgraph image of bacteria colony internal structure (the red circle indicates the area of bacteria colony shown on the microscopic image), (b) microscopic image of analyzed area of the colony, (c) Fresnel diffraction pattern of Escherichia coli colony (approx. beam diameter 2 mm), (d) the same Fresnel pattern in case of smaller diameter of the laser beam (approx. beam diameter 1.5 mm).
) colony has shown some heterogeneities inside the structure of the colony exposed to the 0°C for 20 minutes. They are also observed on the microscopic image (see Fig. 9(b)). These heterogeneities caused the diffraction pattern changes seen in the region of second diffraction ring. Simultaneously, the colony internal structure, was also influenced (see Fig. 9(c), 9(d)). In analyzed case, the first ring maximum is not so evidently presented on Fig. 9(c), but after decreasing the diameter of the laser beam, it is observed in the center of the diffraction pattern on Fig. 9(d).

4.3 The influence of the nutrient medium on the Fresnel diffraction pattern of bacteria colony

As it was previously mentioned, various grown conditions can affect the morphological properties of bacteria colonies and in consequence their diffraction patterns. In this section, the dependence of the Fresnel diffraction patterns of the Escherichia coli (0119) colonies from the kind of the used nutrient medium, will be analyzed. Three nutrient media MacConkey, nutrient agar and Columbia agar, were examined. Bacteria colonies were incubated at 37 °C for 12 hours and their Fresnel diffraction patterns were recorded after 14, 22, 36 and 40 hours. The beam diameter was approximately equal to the diameter of illuminated bacterial colony. The diameter of the bacterial colony after 14, 22, 36 and 40 hours of incubation was approximately equal: 500 μm, 1000 μm, 1500 μm and 2100 μm for Columbia agar, 500 μm, 1200 μm, 1900 μm and 2500 μm for MacConkey medium; 850 μm, 1300 μm, 2000 μm and 2300 μm for nutrient agar, respectively.

Microscopic images of exemplary bacteria colonies also showed the differences between the colonies structures (see Fig. 11
Fig. 11 Microscopic images of Escherichia coli colonies grown on: (a) Columbia agar, (b) MacConkey medium, (c) nutrient agar.
). The change of the bacteria colony diameter directly indicates the influence of the kind of used nutrient medium on the colony structure. The most significant differences in the colony transmission properties were observed in the case of bacteria colonies grown on MacConkey agar. It was caused by dyeing the bacteria colonies, because bacteria cells are decomposing the lactose contained in the nutrient medium.

5. Discussion

The complex physical model of light transformation in optical system with converging spherical wave illumination, which was widely used in optical information processing for analysis of flat transparencies, can by applied for analysis of light diffraction by bacteria colonies. To prove the theoretical predictions of proposed model, the additional computational simulations were performed in MatLab environment. Achieved results (see Fig. 13
Fig. 13 The computational simulations of diffraction patterns of the circular aperture with the same observation distances as on Fig. 5.
) for circular aperture with the same radius and observation distances as presented on Fig. 5 have shown that our approach can predict the experimental diffraction patterns. It was demonstrated that it is possible to compress the observation space in proposed optical system to observe both Fresnel and Fraunhofer diffraction patterns, as well. However, it should be pointed out that some modification should be introduced taking into account the presence of additional phase modulation of bacteria colonies caused by their shapes. This modulation affects the main properties of the optical system, because the Fraunhofer patterns in general will be not observed in the back focal plane of the transforming lens, but the observation plane will be shifted to another location depending on the colony curvature.

However, all other advantages of analyzed optical system as scaling, possibility of observation of Fresnel and Fraunhofer patterns, low level of optical aberrations etc. are preserved. Obtained experimental results have shown that in the proposed system it is possible to control the scale of bacteria colonies diffraction patterns by changing the location of the sample respectively to the fixed locations of the transforming lens and camera.

Performed experiments have shown that in the analysis of bacteria diffraction patterns growth conditions should be taken into the careful consideration. In the case of various incubation temperatures, it was shown that the observed Fresnel diffraction patterns exhibit significant differences. In general, basing on microscopic and phase contrast images one can distinguish in the bacteria colony two zones with different transmission properties in the center and edges areas. Central, circular shaped zone has low 2D transmission coefficient around 0.3-0.4 and second concentric zone has higher 2D transmission coefficient around 0.7-0.8. This corresponds to the colony state, since in the center of colony the oldest bacteria cells are located and the higher concentration of the extracellular material is observed. These factors are causing higher mass density in the center of the colony and in consequence lower transmission in this region than in the region near the colony edges. Therefore, the resulting diffraction patterns can be considered in term of knife edge diffraction phenomena on each transmission zone of bacteria colony. It is a similar effect as in the case of light diffraction on annular aperture or on Fresnel plate zones with different transmission coefficient. The structure of the diffraction patterns are generally affected by circular shape of these zones, as well as their transmission. Moreover, since the beam diameter slightly exceed the lateral size of bacteria colony, the part of the beam is attenuated and transmitted by the colony, therefore it means that bacteria colony can by treated as a phase and amplitude aperture, which is creating the diffraction rings in the observation plane. Additional radial spokes observed in Fresnel diffraction patterns are caused by arc-shaped features occurred near the region of colony edges, presented in the bacterial colony as it was already reported [36

36. E. Bae, P. P. Banada, K. Huff, A. K. Bhunia, J. P. Robinson, and E. D. Hirleman, “Biophysical modeling of forward scattering from bacterial colonies using scalar diffraction theory,” Appl. Opt. 46(17), 3639–3648 (2007). [CrossRef] [PubMed]

]. The effect of the influence of the incubation temperature on Fresnel patterns is more evident, in the case of bacteria colonies incubated in lower temperature, since in this case apart the lower diameter of the colony, the heterogeneity of their internal zones structure, particularly near their edges, is observed in comparison to the bacteria colonies grown in standard, higher temperature of incubation (see Fig. 9 and Fig. 10). In most cases, the deformation of the circular shape of the zone near the bacteria colony edges is observed, therefore the second diffraction ring observed in Fresnel patterns of bacteria colony is affected, what was experimentally demonstrated.

Results presented in the Section 4.3 have shown that the Fresnel diffraction patterns are also affected by the kind of used nutrient medium on which the bacteria cells were seeded. Different chemical compositions of the nutrient media cause the changes of bacterial colony morphology, size and its transmission properties. For Columbia agar for longer incubation times, the second round maximum occurs inside the region of the colony shadow and the diameter of the diffraction rings decreases. In our opinion, taking account the scalar theory of diffraction, this effect can be caused by the change of the size of bacterial colony, as well as the size of the zones with different 2D transmission coefficients inside the colony. According to the Eq. (22), the bacterial colony diffraction pattern can be treated as a Fourier transform of the colony amplitude transmittance (see Eq. (11)), therefore according to the similarity theorem of the Fourier transform [46

46. J. W. Goodman, Introduction to Fourier Optics, 3rd ed. (Robert & Company Publishers, 2005).

], when the diameter of bacterial colony and diameter of internal zones of colony with different transmission properties are increased with the increasing of the incubation time, the diameter of the diffraction ring of Fresnel patterns decreased. This effect can explain the observed behavior of the diffraction patterns changes depending of the type of the incubation time. However, it should be pointed out that some significant influence of central thickness of bacterial colony on maximal diffraction angle and on number of diffraction rings, is observed [41

41. E. Bae, N. Bai, A. Aroonnual, J. P. Robinson, A. K. Bhunia, and E. D. Hirleman, “Modeling light propagation through bacterial colonies and its correlation with forward scattering patterns,” J. Biomed. Opt. 15(4), 045001 (2010). [CrossRef] [PubMed]

]. Therefore, the maximum diffraction angle depends on the diameter of the colony, but as well on the central thickness of the colony. In the case of MacConkey medium, the additional effect of bacterial colony dyeing is observed. Therefore, practically the central zone of bacterial colony is completely attenuates the incident laser beam and the 2D transmission coefficient is around zero (see Fig. 14
Fig. 14 The microscopic image of the Escherichia coli colony grown on MacConkey medium after 22 hours of incubation with additional spectral filter increasing the contrast.
). This means that the central zone of the colony acts as a classical opaque obstacle.

After 22 hours of the incubation this central zone does not exceed the diameter of bacterial colony, therefore the diffraction ring observed in the Fresnel pattern is located inside the colony shadow. However for longer times of incubation the entire colony is completely non-transparent, therefore the diffraction on the bacterial colony edges is dominating. Moreover, the presence of the additional precipitated bile salts near the colony edges are affecting the Fresnel diffraction pattern, as well.

In the case of nutrient agar, the difference of 2D transmission coefficients of the zones of the bacterial colony with different transmission properties were lower than 0.2, therefore the most significant factor is the difference of transmission coefficients between the bacteria colony and the agar, near the region of colony edges. The radial spokes observed in Fresnel diffraction patterns were caused by arc-shaped features and irregular shape of colony edges. These results additionally indicate that the kind of used nutrient media can affect the transmission properties of bacterial colony and in consequences the diffraction patterns.

Experimental results and theoretical considerations indicate that the incubation temperature, as well as the kind of used nutrient medium, significantly affect the colony morphology and in consequence diffraction patterns. These factors are crucial for the bacteria identification based on colonies diffraction patterns. One has to notice that standardization conditions must be introduced to ensure the repeatability of observed Fresnel diffraction patterns. Moreover, presented results have shown the potential of proposed optical system with converging spherical wave illumination to distinguish the morphological and physiological differences between analyzed bacterial colonies.

6. Conclusions

Proposed optical system with converging spherical wave illumination, which was not so far used for analysis of bacteria colonies diffraction patterns, has some significant advantages including diffraction pattern scaling, compression of observation space, low level of optical aberrations and simple calibration. Particularly important are the scaling properties, since the size of used camera matrix may be conveniently chosen. The complex model of light transformation, including the phase modulation of the bacteria colony profile, explaining the light diffraction in the proposed optical system, was presented. Obtained experimental results have shown high correlation between Fresnel diffraction patterns of the bacteria colonies and the morphological structure of the colony. Moreover, it was shown that bacteria culture conditions can affect the spatial structure of diffraction patterns. Proposed optical system enables the nondestructive and noninvasive optical examination of bacteria colonies under the most standard, microbiological procedure of bacteria breeding. Moreover, the bacteria samples can be used for further verification or investigation.

Acknowledgment

This work was partially supported by the Research Grant from the Polish Ministry of Science and Higher Education (No N N505 557739). The support of the European Union under the European Social Fund (No DG-G/2589/10) is gratefully acknowledged, as well.

References and links

1.

K. Christen, “Bioterrorism and waterborne pathogens: how big is the threat?” Environ. Sci. Technol. 35(19), 396A–397A (2001). [CrossRef] [PubMed]

2.

A. M. Nicol, Ch. Hurrell, W. McDowall, K. Bartlett, and N. Elmieh, “Communicating the risks of a new, emerging pathogen: the case of Cryptococcus gattii,” Risk Anal. 28(2), 373–386 (2008). [CrossRef] [PubMed]

3.

C. Dennis, “The bugs of war,” Nature 411(6835), 232–235 (2001). [CrossRef] [PubMed]

4.

T. Ersek and Z. Nagy, “Species hybrids in the genus Phytophthora with emphasis on the alder pathogen Phytophthora alni: a review,” Eur. J. Plant Pathol. 22(1), 31–39 (2010).

5.

S. B. Levy and B. Marshall, “Antibacterial resistance worldwide: causes, challenges and responses,” Nat. Med. 10(12Suppl), S122–S129 (2004). [CrossRef] [PubMed]

6.

S. G. B. Amyes, “The rise in bacterial resistance,” Br. Med. J. 320(7229), 199–200 (2000). [CrossRef] [PubMed]

7.

A. S. Colsky, R. S. Kirsner, and F. A. Kerdel, “Analysis of antibiotic susceptibilities of skin wound flora in hospitalized dermatology patients. The crisis of antibiotic resistance has come to the surface,” Arch. Dermatol. 134(8), 1006–1009 (1998). [CrossRef] [PubMed]

8.

http://www.idph.state.ia.us/adper/common/pdf/abx/tab9_niaid_resistance.pdf

9.

A. C. Samuels, A. P. Snyder, D. K. Emge, D. Amant, J. Minter, M. Campbell, and A. Tripathi, “Classification of select category A and B bacteria by Fourier transform infrared spectroscopy,” Appl. Spectrosc. 63(1), 14–24 (2009). [CrossRef] [PubMed]

10.

D. Ivnitski, I. Abdel-Hamid, P. Atanasov, and E. Wilkins, “Biosensors for detection of pathogenic bacteria,” Biosens. Bioelectron. 14(7), 599–624 (1999). [CrossRef]

11.

Y. L. Pan, S. Holler, R. K. Chang, S. C. Hill, R. G. Pinnick, S. Niles, and J. R. Bottiger, “Single-shot fluorescence spectra of individual micrometer-sized bioaerosols illuminated by a 351- or a 266-nm ultraviolet laser,” Opt. Lett. 24(2), 116–118 (1999). [CrossRef] [PubMed]

12.

S. C. Hill, R. G. Pinnick, S. Niles, N. F. Fell Jr, Y. L. Pan, J. Bottiger, B. V. Bronk, S. Holler, and R. K. Chang, “Fluorescence from airborne microparticles: dependence on size, concentration of fluorophores, and illumination intensity,” Appl. Opt. 40(18), 3005–3013 (2001). [CrossRef] [PubMed]

13.

R. G. Pinnick, S. C. Hill, S. Niles, D. M. Garvey, Y.-L. Pan, S. Holler, R. K. Chang, J. Bottiger, B. V. Bronk, B. T. Chen, C.-S. Orr, and G. Feather, “Real–time measurement of fluorescence spectra from single airborne biological particles,” Field Anal. Chem. Technol. 3(4-5), 221–239 (1999). [CrossRef]

14.

A. Maninen, M. Putkiranta, A. Rostedt, J. Saarela, T. Laurila, M. Marjamäki, J. Keskinen, and R. Hernberg, “Instrumentation for measuring fluorescence cross-sections from airborne microsized particle,” Appl. Opt. 47(7), 110–115 (2008).

15.

S. Sarasanandarajah, J. Kunnil, B. V. Bronk, and L. Reinisch, “Two-dimensional multiwavelength fluorescence spectra of dipicolinic acid and calcium dipicolinate,” Appl. Opt. 44(7), 1182–1187 (2005). [CrossRef] [PubMed]

16.

A. Alimova, A. Katz, P. Gottlieb, and R. R. Alfano, “Proteins and dipicolinic acid released during heat shock activation of Bacillus subtilis spores probed by optical spectroscopy,” Appl. Opt. 45(3), 445–450 (2006). [CrossRef] [PubMed]

17.

G. W. Faris, R. A. Copeland, K. Mortelmans, and B. V. Bronk, “Spectrally resolved absolute fluorescence cross sections for bacillus spores,” Appl. Opt. 36(4), 958–967 (1997). [CrossRef] [PubMed]

18.

A. Thomas, D. Sands, D. Baum, L. To, and G. O. Rubel, “Emission wavelength dependence of fluorescence lifetimes of bacteriological spores and pollens,” Appl. Opt. 45(25), 6634–6639 (2006). [CrossRef] [PubMed]

19.

L. J. Radziemski, “From LASER to LIBS, the path of technology development,” Spectrochim. Acta, B At. Spectrosc. 57(7), 1109–1113 (2002). [CrossRef]

20.

S. Morel, N. Leone, P. Adam, and J. Amouroux, “Detection of bacteria by time-resolved laser-induced breakdown spectroscopy,” Appl. Opt. 42(30), 6184–6191 (2003). [CrossRef] [PubMed]

21.

J. Thomason, “Spectroscopy takes security into the field,” Photon. Spectra 38, 83–85 (2004).

22.

R. T. Noble and S. B. Weisberg, “A review of technologies for rapid detection of bacteria in recreational waters,” J. Water Health 3(4), 381–392 (2005). [PubMed]

23.

D. L. Rosen, “Bacterial endospores detection using photoluminescence from terbium dipicolinate,” Rev. Anal. Chem. 18(1-2), 1–22 (1999). [CrossRef]

24.

D. L. Rosen, “Airborne bacterial endospores detected by use of an impinger containing aqueous terbium chloride,” Appl. Opt. 45(13), 3152–3157 (2006). [CrossRef] [PubMed]

25.

S. J. Mechery, X. J. Zhao, L. Wang, L. R. Hilliard, A. Munteanu, and W. Tan, “Using bioconjugated nanoparticles to monitor E. coli in a flow channel,” Chem. Asian J. 1(3), 384–390 (2006). [CrossRef] [PubMed]

26.

W. Lian, S. A. Litherland, H. Badrane, W. Tan, D. Wu, H. V. Baker, P. A. Gulig, D. V. Lim, and S. Jin, “Ultrasensitive detection of biomolecules with fluorescent dye-doped nanoparticles,” Anal. Biochem. 334(1), 135–144 (2004). [CrossRef] [PubMed]

27.

J. Homola, J. Dostálek, S. Chen, A. Rasooly, S. Jiang, and S. S. Yee, “Spectral surface plasmon resonance biosensor for detection of staphylococcal enterotoxin B in milk,” Int. J. Food Microbiol. 75(1-2), 61–69 (2002). [CrossRef] [PubMed]

28.

P. Leonard, S. Hearty, J. Quinn, and R. O’Kennedy, “A generic approach for the detection of whole Listeria monocytogenes cells in contaminated samples using surface plasmon resonance,” Biosens. Bioelectron. 19(10), 1331–1335 (2004). [CrossRef] [PubMed]

29.

A. Subramanian, J. Irudayaraj, and T. Ryan, “A mixed self-assembled monolayer-based surface plasmon immunosensor for detection of E. coli O157:H7,” Biosens. Bioelectron. 21(7), 998–1006 (2006). [CrossRef] [PubMed]

30.

P. J. Wyatt, “Differential light scattering: a physical method for identifying living bacterial cells,” Appl. Opt. 7(10), 1879–1896 (1968). [CrossRef] [PubMed]

31.

P. H. Kaye, J. E. Barton, E. Hirst, and J. M. Clark, “Simultaneous light scattering and intrinsic fluorescence measurement for the classification of airborne particles,” Appl. Opt. 39(21), 3738–3745 (2000). [CrossRef] [PubMed]

32.

Y. L. Pan, K. B. Aptowicz, R. K. Chang, M. Hart, and J. D. Eversole, “Characterizing and monitoring respiratory aerosols by light scattering,” Opt. Lett. 28(8), 589–591 (2003). [CrossRef] [PubMed]

33.

S. Holler, S. Zomer, G. F. Crosta, Y. L. Pan, R. K. Chang, and J. R. Bottiger, “Multivariate analysis and classification of two-dimensional angular optical scattering patterns from aggregates,” Appl. Opt. 43(33), 6198–6206 (2004). [CrossRef] [PubMed]

34.

G. E. Fernandes, Y. L. Pan, R. K. Chang, K. Aptowicz, and R. G. Pinnick, “Simultaneous forward- and backward-hemisphere elastic-light-scattering patterns of respirable-size aerosols,” Opt. Lett. 31(20), 3034–3036 (2006). [CrossRef] [PubMed]

35.

J. C. Auger, K. B. Aptowicz, R. G. Pinnick, Y.-L. Pan, and R. K. Chang, “Angularly resolved light scattering from aerosolized spores: observations and calculations,” Opt. Lett. 32(22), 3358–3360 (2007). [CrossRef] [PubMed]

36.

E. Bae, P. P. Banada, K. Huff, A. K. Bhunia, J. P. Robinson, and E. D. Hirleman, “Biophysical modeling of forward scattering from bacterial colonies using scalar diffraction theory,” Appl. Opt. 46(17), 3639–3648 (2007). [CrossRef] [PubMed]

37.

M. Venkatapathi, B. Rajwa, K. Ragheb, P. P. Banada, T. Lary, J. P. Robinson, and E. D. Hirleman, “High speed classification of individual bacterial cells using a model-based light scatter system and multivariate statistics,” Appl. Opt. 47(5), 678–686 (2008). [CrossRef] [PubMed]

38.

P. P. Banada, S. Guo, B. Bayraktar, E. Bae, B. Rajwa, J. P. Robinson, E. D. Hirleman, and A. K. Bhunia, “Optical forward-scattering for detection of Listeria monocytogenes and other Listeria species,” Biosens. Bioelectron. 22(8), 1664–1671 (2007). [CrossRef] [PubMed]

39.

E. Bae, P. P. Banada, K. Huff, A. K. Bhunia, J. P. Robinson, and E. D. Hirleman, “Analysis of time-resolved scattering from macroscale bacterial colonies,” J. Biomed. Opt. 13(1), 014010 (2008). [CrossRef] [PubMed]

40.

P. P. Banada, K. Huff, E. Bae, B. Rajwa, A. Aroonnual, B. Bayraktar, A. Adil, J. P. Robinson, E. D. Hirleman, and A. K. Bhunia, “Label-free detection of multiple bacterial pathogens using light-scattering sensor,” Biosens. Bioelectron. 24(6), 1685–1692 (2009). [CrossRef] [PubMed]

41.

E. Bae, N. Bai, A. Aroonnual, J. P. Robinson, A. K. Bhunia, and E. D. Hirleman, “Modeling light propagation through bacterial colonies and its correlation with forward scattering patterns,” J. Biomed. Opt. 15(4), 045001 (2010). [CrossRef] [PubMed]

42.

E. Bae, A. Aroonnual, A. K. Bhunia, and E. D. Hirleman, “On the sensitivity of forward scattering patterns from bacterial colonies to media composition,” J. Biophotonics 4(4), 236–243 (2011). [CrossRef] [PubMed]

43.

I. Buzalewicz, K. Wysocka, and H. Podbielska, “Exploiting of optical transforms for bacteria evaluation in vitro,” Proc. SPIE 7371, 73711H, 73711H-6 (2009). [CrossRef]

44.

I. Buzalewicz, K. Wysocka-Król, and H. Podbielska, “Image processing guided analysis for estimation of bacteria colonies number by means of optical transforms,” Opt. Express 18(12), 12992–13005 (2010). [CrossRef] [PubMed]

45.

I. Buzalewicz, K. Wysocka–Król, K. Kowal, and H. Podbielska, “Evaluation of antibacterial agents efficiency,” in Information Technologies in Biomedicine 2, E. Pietka, J. Kawa ed. (Springer-Verlag, 2010).

46.

J. W. Goodman, Introduction to Fourier Optics, 3rd ed. (Robert & Company Publishers, 2005).

47.

J. D. Gaskill, Linear Systems, Fourier Transform and Optics, (John Wiley & Sons, 1978).

48.

D. Joyeux and S. Lowenthal, “Optical Fourier transform: what is the optimal setup?” Appl. Opt. 21(23), 4368–4372 (1982). [CrossRef] [PubMed]

49.

M. A. Bees, P. Andresén, E. Mosekilde, and M. Givskov, “The interaction of thin-film flow, bacterial swarming and cell differentiation in colonies of Serratia liquefaciens,” J. Math. Biol. 40(1), 27–63 (2000). [CrossRef] [PubMed]

OCIS Codes
(170.0110) Medical optics and biotechnology : Imaging systems
(170.0170) Medical optics and biotechnology : Medical optics and biotechnology
(170.4580) Medical optics and biotechnology : Optical diagnostics for medicine
(290.2558) Scattering : Forward scattering

ToC Category:
Medical Optics and Biotechnology

History
Original Manuscript: July 7, 2011
Revised Manuscript: September 10, 2011
Manuscript Accepted: October 2, 2011
Published: October 20, 2011

Virtual Issues
Vol. 6, Iss. 11 Virtual Journal for Biomedical Optics

Citation
Igor Buzalewicz, Alina Wieliczko, and Halina Podbielska, "Influence of various growth conditions on Fresnel diffraction patterns of bacteria colonies examined in the optical system with converging spherical wave illumination," Opt. Express 19, 21768-21785 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-22-21768


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. K. Christen, “Bioterrorism and waterborne pathogens: how big is the threat?” Environ. Sci. Technol.35(19), 396A–397A (2001). [CrossRef] [PubMed]
  2. A. M. Nicol, Ch. Hurrell, W. McDowall, K. Bartlett, and N. Elmieh, “Communicating the risks of a new, emerging pathogen: the case of Cryptococcus gattii,” Risk Anal.28(2), 373–386 (2008). [CrossRef] [PubMed]
  3. C. Dennis, “The bugs of war,” Nature411(6835), 232–235 (2001). [CrossRef] [PubMed]
  4. T. Ersek and Z. Nagy, “Species hybrids in the genus Phytophthora with emphasis on the alder pathogen Phytophthora alni: a review,” Eur. J. Plant Pathol.22(1), 31–39 (2010).
  5. S. B. Levy and B. Marshall, “Antibacterial resistance worldwide: causes, challenges and responses,” Nat. Med.10(12Suppl), S122–S129 (2004). [CrossRef] [PubMed]
  6. S. G. B. Amyes, “The rise in bacterial resistance,” Br. Med. J.320(7229), 199–200 (2000). [CrossRef] [PubMed]
  7. A. S. Colsky, R. S. Kirsner, and F. A. Kerdel, “Analysis of antibiotic susceptibilities of skin wound flora in hospitalized dermatology patients. The crisis of antibiotic resistance has come to the surface,” Arch. Dermatol.134(8), 1006–1009 (1998). [CrossRef] [PubMed]
  8. http://www.idph.state.ia.us/adper/common/pdf/abx/tab9_niaid_resistance.pdf
  9. A. C. Samuels, A. P. Snyder, D. K. Emge, D. Amant, J. Minter, M. Campbell, and A. Tripathi, “Classification of select category A and B bacteria by Fourier transform infrared spectroscopy,” Appl. Spectrosc.63(1), 14–24 (2009). [CrossRef] [PubMed]
  10. D. Ivnitski, I. Abdel-Hamid, P. Atanasov, and E. Wilkins, “Biosensors for detection of pathogenic bacteria,” Biosens. Bioelectron.14(7), 599–624 (1999). [CrossRef]
  11. Y. L. Pan, S. Holler, R. K. Chang, S. C. Hill, R. G. Pinnick, S. Niles, and J. R. Bottiger, “Single-shot fluorescence spectra of individual micrometer-sized bioaerosols illuminated by a 351- or a 266-nm ultraviolet laser,” Opt. Lett.24(2), 116–118 (1999). [CrossRef] [PubMed]
  12. S. C. Hill, R. G. Pinnick, S. Niles, N. F. Fell, Y. L. Pan, J. Bottiger, B. V. Bronk, S. Holler, and R. K. Chang, “Fluorescence from airborne microparticles: dependence on size, concentration of fluorophores, and illumination intensity,” Appl. Opt.40(18), 3005–3013 (2001). [CrossRef] [PubMed]
  13. R. G. Pinnick, S. C. Hill, S. Niles, D. M. Garvey, Y.-L. Pan, S. Holler, R. K. Chang, J. Bottiger, B. V. Bronk, B. T. Chen, C.-S. Orr, and G. Feather, “Real–time measurement of fluorescence spectra from single airborne biological particles,” Field Anal. Chem. Technol.3(4-5), 221–239 (1999). [CrossRef]
  14. A. Maninen, M. Putkiranta, A. Rostedt, J. Saarela, T. Laurila, M. Marjamäki, J. Keskinen, and R. Hernberg, “Instrumentation for measuring fluorescence cross-sections from airborne microsized particle,” Appl. Opt.47(7), 110–115 (2008).
  15. S. Sarasanandarajah, J. Kunnil, B. V. Bronk, and L. Reinisch, “Two-dimensional multiwavelength fluorescence spectra of dipicolinic acid and calcium dipicolinate,” Appl. Opt.44(7), 1182–1187 (2005). [CrossRef] [PubMed]
  16. A. Alimova, A. Katz, P. Gottlieb, and R. R. Alfano, “Proteins and dipicolinic acid released during heat shock activation of Bacillus subtilis spores probed by optical spectroscopy,” Appl. Opt.45(3), 445–450 (2006). [CrossRef] [PubMed]
  17. G. W. Faris, R. A. Copeland, K. Mortelmans, and B. V. Bronk, “Spectrally resolved absolute fluorescence cross sections for bacillus spores,” Appl. Opt.36(4), 958–967 (1997). [CrossRef] [PubMed]
  18. A. Thomas, D. Sands, D. Baum, L. To, and G. O. Rubel, “Emission wavelength dependence of fluorescence lifetimes of bacteriological spores and pollens,” Appl. Opt.45(25), 6634–6639 (2006). [CrossRef] [PubMed]
  19. L. J. Radziemski, “From LASER to LIBS, the path of technology development,” Spectrochim. Acta, B At. Spectrosc.57(7), 1109–1113 (2002). [CrossRef]
  20. S. Morel, N. Leone, P. Adam, and J. Amouroux, “Detection of bacteria by time-resolved laser-induced breakdown spectroscopy,” Appl. Opt.42(30), 6184–6191 (2003). [CrossRef] [PubMed]
  21. J. Thomason, “Spectroscopy takes security into the field,” Photon. Spectra38, 83–85 (2004).
  22. R. T. Noble and S. B. Weisberg, “A review of technologies for rapid detection of bacteria in recreational waters,” J. Water Health3(4), 381–392 (2005). [PubMed]
  23. D. L. Rosen, “Bacterial endospores detection using photoluminescence from terbium dipicolinate,” Rev. Anal. Chem.18(1-2), 1–22 (1999). [CrossRef]
  24. D. L. Rosen, “Airborne bacterial endospores detected by use of an impinger containing aqueous terbium chloride,” Appl. Opt.45(13), 3152–3157 (2006). [CrossRef] [PubMed]
  25. S. J. Mechery, X. J. Zhao, L. Wang, L. R. Hilliard, A. Munteanu, and W. Tan, “Using bioconjugated nanoparticles to monitor E. coli in a flow channel,” Chem. Asian J.1(3), 384–390 (2006). [CrossRef] [PubMed]
  26. W. Lian, S. A. Litherland, H. Badrane, W. Tan, D. Wu, H. V. Baker, P. A. Gulig, D. V. Lim, and S. Jin, “Ultrasensitive detection of biomolecules with fluorescent dye-doped nanoparticles,” Anal. Biochem.334(1), 135–144 (2004). [CrossRef] [PubMed]
  27. J. Homola, J. Dostálek, S. Chen, A. Rasooly, S. Jiang, and S. S. Yee, “Spectral surface plasmon resonance biosensor for detection of staphylococcal enterotoxin B in milk,” Int. J. Food Microbiol.75(1-2), 61–69 (2002). [CrossRef] [PubMed]
  28. P. Leonard, S. Hearty, J. Quinn, and R. O’Kennedy, “A generic approach for the detection of whole Listeria monocytogenes cells in contaminated samples using surface plasmon resonance,” Biosens. Bioelectron.19(10), 1331–1335 (2004). [CrossRef] [PubMed]
  29. A. Subramanian, J. Irudayaraj, and T. Ryan, “A mixed self-assembled monolayer-based surface plasmon immunosensor for detection of E. coli O157:H7,” Biosens. Bioelectron.21(7), 998–1006 (2006). [CrossRef] [PubMed]
  30. P. J. Wyatt, “Differential light scattering: a physical method for identifying living bacterial cells,” Appl. Opt.7(10), 1879–1896 (1968). [CrossRef] [PubMed]
  31. P. H. Kaye, J. E. Barton, E. Hirst, and J. M. Clark, “Simultaneous light scattering and intrinsic fluorescence measurement for the classification of airborne particles,” Appl. Opt.39(21), 3738–3745 (2000). [CrossRef] [PubMed]
  32. Y. L. Pan, K. B. Aptowicz, R. K. Chang, M. Hart, and J. D. Eversole, “Characterizing and monitoring respiratory aerosols by light scattering,” Opt. Lett.28(8), 589–591 (2003). [CrossRef] [PubMed]
  33. S. Holler, S. Zomer, G. F. Crosta, Y. L. Pan, R. K. Chang, and J. R. Bottiger, “Multivariate analysis and classification of two-dimensional angular optical scattering patterns from aggregates,” Appl. Opt.43(33), 6198–6206 (2004). [CrossRef] [PubMed]
  34. G. E. Fernandes, Y. L. Pan, R. K. Chang, K. Aptowicz, and R. G. Pinnick, “Simultaneous forward- and backward-hemisphere elastic-light-scattering patterns of respirable-size aerosols,” Opt. Lett.31(20), 3034–3036 (2006). [CrossRef] [PubMed]
  35. J. C. Auger, K. B. Aptowicz, R. G. Pinnick, Y.-L. Pan, and R. K. Chang, “Angularly resolved light scattering from aerosolized spores: observations and calculations,” Opt. Lett.32(22), 3358–3360 (2007). [CrossRef] [PubMed]
  36. E. Bae, P. P. Banada, K. Huff, A. K. Bhunia, J. P. Robinson, and E. D. Hirleman, “Biophysical modeling of forward scattering from bacterial colonies using scalar diffraction theory,” Appl. Opt.46(17), 3639–3648 (2007). [CrossRef] [PubMed]
  37. M. Venkatapathi, B. Rajwa, K. Ragheb, P. P. Banada, T. Lary, J. P. Robinson, and E. D. Hirleman, “High speed classification of individual bacterial cells using a model-based light scatter system and multivariate statistics,” Appl. Opt.47(5), 678–686 (2008). [CrossRef] [PubMed]
  38. P. P. Banada, S. Guo, B. Bayraktar, E. Bae, B. Rajwa, J. P. Robinson, E. D. Hirleman, and A. K. Bhunia, “Optical forward-scattering for detection of Listeria monocytogenes and other Listeria species,” Biosens. Bioelectron.22(8), 1664–1671 (2007). [CrossRef] [PubMed]
  39. E. Bae, P. P. Banada, K. Huff, A. K. Bhunia, J. P. Robinson, and E. D. Hirleman, “Analysis of time-resolved scattering from macroscale bacterial colonies,” J. Biomed. Opt.13(1), 014010 (2008). [CrossRef] [PubMed]
  40. P. P. Banada, K. Huff, E. Bae, B. Rajwa, A. Aroonnual, B. Bayraktar, A. Adil, J. P. Robinson, E. D. Hirleman, and A. K. Bhunia, “Label-free detection of multiple bacterial pathogens using light-scattering sensor,” Biosens. Bioelectron.24(6), 1685–1692 (2009). [CrossRef] [PubMed]
  41. E. Bae, N. Bai, A. Aroonnual, J. P. Robinson, A. K. Bhunia, and E. D. Hirleman, “Modeling light propagation through bacterial colonies and its correlation with forward scattering patterns,” J. Biomed. Opt.15(4), 045001 (2010). [CrossRef] [PubMed]
  42. E. Bae, A. Aroonnual, A. K. Bhunia, and E. D. Hirleman, “On the sensitivity of forward scattering patterns from bacterial colonies to media composition,” J. Biophotonics4(4), 236–243 (2011). [CrossRef] [PubMed]
  43. I. Buzalewicz, K. Wysocka, and H. Podbielska, “Exploiting of optical transforms for bacteria evaluation in vitro,” Proc. SPIE7371, 73711H, 73711H-6 (2009). [CrossRef]
  44. I. Buzalewicz, K. Wysocka-Król, and H. Podbielska, “Image processing guided analysis for estimation of bacteria colonies number by means of optical transforms,” Opt. Express18(12), 12992–13005 (2010). [CrossRef] [PubMed]
  45. I. Buzalewicz, K. Wysocka–Król, K. Kowal, and H. Podbielska, “Evaluation of antibacterial agents efficiency,” in Information Technologies in Biomedicine 2, E. Pietka, J. Kawa ed. (Springer-Verlag, 2010).
  46. J. W. Goodman, Introduction to Fourier Optics, 3rd ed. (Robert & Company Publishers, 2005).
  47. J. D. Gaskill, Linear Systems, Fourier Transform and Optics, (John Wiley & Sons, 1978).
  48. D. Joyeux and S. Lowenthal, “Optical Fourier transform: what is the optimal setup?” Appl. Opt.21(23), 4368–4372 (1982). [CrossRef] [PubMed]
  49. M. A. Bees, P. Andresén, E. Mosekilde, and M. Givskov, “The interaction of thin-film flow, bacterial swarming and cell differentiation in colonies of Serratia liquefaciens,” J. Math. Biol.40(1), 27–63 (2000). [CrossRef] [PubMed]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited