Chemotaxis has a meaningful role in several fields, such as microbial physiology, medicine and biotechnology. We present a new application of dynamic laser speckle (or biospeckle) to detect different degrees of bacterial motility during chemotactic response experiments. Encouraging results showed different bacterial dynamic responses due to differences in the hardness of the support in the swarming plates. We compare this method to a conventional technique that uses white light. Both methods showed to be analogous and, in some cases, complementary. The results suggest that biospeckle processed images can be used as an alternative method to evaluate bacterial chemotactic response and can supply additional information about the bacterial motility in different areas of the swarm plate assay that might be useful for biological analysis.

This review article summarizes some recent insights into the strategies used by marine organisms to select surfaces for colonization. While larger organisms rely on their sensory machinery to select surfaces, smaller microorganisms developed less complex but still effective ways to probe interfaces. Two examples, zoospores of algae and barnacle larvae, are discussed and both appear to have build-in test mechanisms to distinguish surfaces with different physicochemical properties. Some systematic studies on the influence of surface cues on exploration, settlement and adhesion are summarized. The intriguing notion that surface colonization resembles a parallelized surface sensing event is discussed towards its complementarity with conventional surface analytical tools. The strategy to populate only selected surfaces seems advantageous as waves, currents and storms constantly challenge adherent soft and hard fouling organism.

We present a method o f analysis of im ages of dynamic speckle based on the filtering in frequency bands of the temporary history of each pixel. Butterworth filters are applied to the temporary evolution, and different im ages are constructed showing the energy in each frequency band. Different degrees of activity of the sample in study, presum ably attributed to different origins, are found. The method is exemplified w ith im ages of bruising damage in fruits and of biological activity in germ inating com seeds. It is found that the activity in the bruised region of an apple differs from the activity of healthy regions in a certain character istic frequency range. The activity of the embryo can also be distinguished from that o f the endosperm in com seeds during germination. © 2005 Optical Society of America OCXS codes: 100.0100, 120.6150, 000.1430.Dynamic speckle or biospeckle is observed in biologi cal samples illuminated by laser light. The properties and applications of this phenomenon have been treated in the literature.1 3 There are several methods for display of speckle pattern activity. Laser speckle contrast analysis,4 proposed by Briers and Webster, uses the local con trast analysis of the integrated time varying speckle in a nonscanning full-field technique for monitoring capillary blood flow. In the method of Fujii et al. ,5 an image display based on the accumulation of differences between images divided by its average shows a microcirculation map of human skin surface. Konishi and Fujii6 used the signal-to-noise ratio in a real time application to visualize a blood flow map of the human retina. The method of Arizaga et al? is based on accumulating all possible differences between con secutive and nonconsecutive frames for each pixel of images in a seed analysis application. Recently other approaches were presented to characterization of atherosclerotic plaque by spatial and temporal speckle pattern analysis8 and to applying time dependent speckle in holographic optical coherence imaging to the study of tumor tissue. 9In the aforementioned methods, the result is a single image that shows a certain measure of the to tal activity of the sample. In this Letter we propose a method with which to analyze biospeckle activity based on decomposition of images in temporary spec tral bands that permits us to obtain several mea sures with a better defined meaning, thus adding to a better detailed characterization of the behavior of the samples.Most algorithms already developed for activity im ages discard time information and pool all the information concerning activity measurement in a single measure. Biological phenomena do not exhibit welldefined frequencies, but, in some cases, they differ in the frequency ranges where energy is concentrated. By using the filters in the frequency domain, one can discriminate phenomena in the sample that occur on different time scales. We present some examples to il lustrate the methodology, but this technique can be extended to other applications of dynamic speckle in biol...

Optical vortex analysis has become an important tool in optical metrology. It has been shown to be able to measure small displacements with up to nanometric precision. We analyze optical vortex behavior in dynamic speckle patterns with the boiling phenomenon. We first study translational patterns with boiling and we find the limitations of the optical vortex metrology. Pure boiling patterns are also evaluated and we find a quantitative descriptor for the activity. We also observe that vortices exhibit a Brownian motion in pure boiling patterns. Numerical and experimental results are shown.

We report on the biodegradation of pure hydrocarbons and chemotaxis towards these compounds by an isolated chlorophenol degrader, Pseudomonas strain H. The biochemical and phylogenetic analysis of the 16S rDNA sequence identified Pseudomonas strain H as having 99.56% similarity with P. aeruginosa PA01. This strain was able to degrade n-hexadecane, 1-undecene, 1-nonene, 1-decene, 1-dodecene and kerosene. It grew in the presence of 1-octene, while this hydrocarbons is toxic to other hydrocarbons degraders. Pseudomonas strain H was also chemotactic towards n-hexadecane, kerosene, 1-undecene and 1-dodecene. These results show that this Pseudomonas strain H is an attractive candidate for hydrocarbon-containing wastewater bioremediation in controlled environments. Since the classical standard techniques for detecting chemotaxis are not efficient at low bacterial concentrations, we demonstrate the use of the dynamic speckle laser method, which is simple and inexpensive, to confirm bacterial chemotaxis at low cell concentrations (less than 10(5) colony-forming unit per millilitre (CFU/mL)) when hydrocarbons are the attractants.

Surface exploration is a key step in the colonization of surfaces by sessile marine biofoulers. As many biofouling organisms can delay settlement until a suitable surface is encountered, colonization can comprise surface exploration and intermittent swimming. As such, the process is best followed in three dimensions. Here we present a low-cost transportable stereoscopic system consisting of two consumer camcorders. We apply this novel apparatus to behavioral analysis of barnacle larvae (≈800 μm length) during surface exploration and extract and analyze the three-dimensional patterns of movement. The resolution of the system and the accuracy of position determination are characterized. As a first practical result, three-dimensional swimming trajectories of the cypris larva of the barnacle Semibalanus balanoides are recorded in the vicinity of a glass surface and close to PEG2000-OH and C11NMe3+Cl− terminated self-assembled monolayers. Although less frequently used in biofouling experiments due to its short reproductive season, the selected model species [Marechal and Hellio (2011), Int Biodeterior Biodegrad, 65(1):92–101] has been used following a number of recent investigations on the settlement behavior on chemically different surfaces [Aldred et al. (2011), ACS Appl Mater Interfaces, 3(6):2085–2091]. Experiments were scheduled to match the availability of cyprids off the north east coast of England so that natural material could be used. In order to demonstrate the biological applicability of the system, analysis of parameters such as swimming direction, swimming velocity and swimming angle are performed.Electronic supplementary materialThe online version of this article (doi:10.1007/s13758-012-0050-x) contains supplementary material, which is available to authorized users.

Abstract. We present a dynamic laser speckle method to easily discriminate filamentous fungi from motile bacteria in soft surfaces, such as agar plate. The method allows the detection and discrimination between fungi and bacteria faster than with conventional techniques. The new procedure could be straightforwardly extended to different micro-organisms, as well as applied to biological and biomedical research, infected tissues analysis, and hospital water and wastewaters studies.

Testing of new coatings to control fouling frequently involves single-species laboratory bioassays. Barnacle cyprids are among the most widely used model organisms in marine biofouling research, and surfaces that inhibit their settlement are considered to be promising candidates for new coating concepts. An analysis of motility parameters (mean velocity and swimming area coefficient) and distribution of cyprids of Balanus amphitrite in different swimming regions in the vicinity of model surfaces (self-assembled monolayers) is presented. The data are correlated with the settlement preferences of cyprids on these surfaces. Cyprids were predominantly found in interfacial regions and the transition frequencies between swimming regions of different depths were determined.