Video processing analysis for the determination and evaluation of the chemotactic response in bacterial populations

Abstract

The aim of the present work was to design a methodology based on video processing to obtain indicators of bacterial population motility that allow the quantitative and qualitative analysis and comparison of the chemotactic phenomenon with different attractants in the agarose-in plug bridge method. Video image sequences were processed applying Shannon's entropy to the intensity time series of each pixel, which conducted to a final pseudo colored image resembling a map of the dynamic bacterial clusters. Processed images could discriminate perfectly between positive and negative attractant responses at different periods of time from the beginning of the assay. An index of spatial and temporal motility was proposed to quantify the bacterial response. With this index, this video processing method allowed obtaining quantitative information of the dynamic changes in space and time from a traditional qualitative assay. We conclude that this computational technique, applied to the traditional agarose-in plug assay, has demonstrated good sensitivity for identifying chemotactic regions with a broad range of motility.

Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors

“…Shannon entropy values for pixels in areas of high bacterial motility will thus be higher than areas of low or no motility. Shannon’s entropy has previously been used in the analysis of time series in numerous fields, including bacterial population motility by Nisenbaum et al (15). Qualitatively identical results were obtained using the two unrelated techniques (Fig.…”

Chemotaxis detection towards chlorophenols using video processing analysis

“…Videos were taken at 1 and 5 min from the beginning of the assay, with phase contrast microscope at 600 × magnification (black & white images). Video images were processed using Shannon's Entropy (Nisenbaum et al, 2016). For each assay, a pseudolored image was composed from the median of the entropy values for each pixel of the five replicates.…”

“…Therefore, the main objective of this study was to characterize the chemotactic response towards CPs by a mixed culture composed of Pseudomonas aeruginosa and Achromobacter marplatensis. We were able to determine this response using the new method of video processing analysis recently published by our group (Nisenbaum et al, 2016) and develop a new tool to determine the mean velocity of the response.…”

“…Therefore, the PC chemotactic response was then tested using the agarose in-plug assay (Yu and Alam, 1997) combined with a video processing analysis recently published by our group (Nisenbaum et al, 2016). The chemotaxis chamber was made with two plastic strips glued to a slide.…”

“…Twenty second-videos were recorded at 1 and 5 min after the inoculation using a CCD camera (Cyber-Shot Sony DSC-W5) with an optical zoom of 1.7, in the B & W mode, at 30 frames per second. Captured images in MPEG format were processed as shown in Nisenbaum et al (2016) using Shannon Entropy (Shannon, 1948) as a descriptor. The active region was divided into subzones of 31.5 μm for further calculations.…”