Hydrocarbon biodegradation and dynamic laser speckle for detecting chemotactic responses at low bacterial concentration

Abstract

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.

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

“…used in this study was isolated from soil and capable of degrading chlorophenols (Murialdo et al, 2003;Wolski et al, 2006;Durruty et al, 2011aDurruty et al, , 2011b. Microorganisms were stored and grew as detailed in a previews work (Nisenbaum et al, 2013).…”

“…Culture in MS was supplemented and incubated as explained by Nisenbaum et al (2013). Strain growth curves were expressed as OD 600 f(t).…”

“…These assays were done as Nisenbaum et al (2013) reported. Chemotactic rings were documented photographically by using the 'bucket of light' described by Parkinson (2007).…”

“…The focus on our work here was to consider the Pseudomonas sp isolated in our laboratory (Murialdo et al, 2003) and capable of metabolising chlorophenols (Wolski et al, 2006) for chemotactic morphology studies. These bacteria also showed hydrocarbon degradation and chemotactic responses to these pollutants (Nisenbaum et al, 2013). The exploration for safe and efficient methods to remove environmental pollutants has its major driving force in the search for novel biosurfactant-producing, chemotactic and multiple toxic compounds-degrading microorganisms.…”

“…Bacterial growth on hydrocarbons as sole sources of carbon and energy lead to slow bacterial growth and low cell yields (Johnsen et al, 2002). A dynamic speckle laser method has been recently tested by our group (Nisenbaum et al, 2013) with toxic compounds metabolisable by bacteria, but the morphology and the activity of the chemotactic colony were ignored. Therefore, the goal of this work is to distinguish motile surface patterns per area of colonisation by applying image processing techniques, in particular fuzzy mathematical morphology (FMM; Bloch and Maitre, 1995;Bloch, 2005) to the laser speckle chemotaxis images.…”