Analysis of bacterial chemotactic response using dynamic laser speckle

Abstract

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.

Dynamic laser speckle and fuzzy mathematical morphology applied to studies of chemotaxis towards hydrocarbons

“…Different assays have been developed to show qualitative bacterial chemotaxis in semisolid and liquid mediums (Jin and Hereld, 2009;Murialdo et al, 2009). In all of them, the spatial bacteria accumulation is observed at different times using white light.…”

“…In these assays, low concentrations of bacteria can hinder the visualisation of the chemotactic bacterial accumulation. We have recently developed a new method for chemotaxis determination, based on dynamic speckle activity segmentation in swim assay (Murialdo et al, 2009). This method allows differentiation of diverse degrees of motility in bacteria.…”

Statistical studies on optical vortices in dynamic speckle fields

“…(3) represents a discrete evaluation of the topological charge that is expressed in Eq. (2). The location of a positive (negative) topological charge is called a positive (negative) vortex.…”

“…Light scattering techniques, including those involving laser speckle analysis have been used to study dynamic biological systems over the last several decades [1][2][3][4]. Speckle based imaging techniques have seen tremendous advancements since the 1990s and are now well-established in the field of biomedical optics [5][6][7].…”

“…Although the existence of these phase singularities have been known since the 1970s, their in-depth study in speckle fields [11] has garnered interest much more recently. (1) where Α( , t) is the amplitude and ( , ) is the phase of the field, both at location r and time t. The real and J of Biomedical Photonics & Eng 4 (2) 27 May 2018 © J-BPE 020301-3 imaginary parts of this speckle field can be separated, with phase singularities occurring in locations where both the real and imaginary parts are zero (Fig. 1).…”