Question

Compare and contrast the functions of the two different signals required for biofilm formation in Pseudomonas aeruginosa and Vibrio cholerae. Essay answers are limited to about 500 words.

Answer 1

All bacteria form biofilms as a strategy for survival and persistence. biofilms are associated with biotic and abiotic surfaces and are composed of aggregates of cells that are encased by a self produced extra cellular matrix. V. cholerae forms biofilms during aquatic and intestinal phases of its life cycle. Both toxigenic and non toxigenic V. cholerae strains live in the aquatic environment year -round ,either in a planktonic state or in a biofilm. When toxigenic strains of vibrio cholerae enter the human host, typically through the ingestion of contaminated water or food, they colonize the small intestine .Biofim formation was quantitatively determined by crystal violet absorption assay. The bacterial response to oxidative stresses evoked by hydrogen peroxide was visualised as a zone of clearing around the disc after 24hr of incubation at 37 degrees C. For both the baterial species studied, biofilm formation was the highest after cultivation in tryptophan soya broth (TSM) being the lowest mineral medium. Vibrio. cholerae non 01 strains were 1.4 to 4.3times more responsive on average oxidative stress depending upon culture medium as compared with Pseudomonas aeruginosa strains. The culture medium had no significant effect on H202 evoked by response to oxidative stress in vibrios contrast to P. aeruginosa, the highest mean resistance to was observed after cultivation in peptone water while the most sensitive cells were found after incubation in TSM+GL and MM.

Conclusion:The oxidative stress had effect on P. aeruginosa