Role of Biological Factors on the Survival of Escherichia coli, Salmonella paratyphi and Vibrio parahaemolyticus in a Tropical Estuary, India
Abhirosh C1, Sheeja KM2, Hatha AAM3, Sherin V4, Thomas AP5
1 School of EnvironmentalSciences, Mahatma Gandhi University, Priyadarsini Hills P.O., Kottayam686 560, Kerala, India.
2 School of Marine Sciences, Cochin Universityof Science and Technology, Cochin, Kerala, India
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Key words: E. coli, S. paratyphi, V. parahaemolyticus, bacteriophages, predation, competition, survival, estuary, India.
Received 3 June 2009; revised 6 August 2009; accepted 12 September 2009.Published 15 October 2009. Available online 15 October 2009.
Microcosm studies have been carried out to evaluate the role of biological factors such as protozoan predation, bacteriophages andautochthonous bacterial competition on the survival of Escherichiacoli, Salmonella paratyphi and Vibrio parahaemolyticus in estuarine water at 20oC and 30oC. The role of protozoans was studied using raw estuarine water. The effect of competing autochthonous bacteria was studied in autoclaved estuarine water inoculated with heterotrophic bacteria isolated from the estuarine water. All the microcosms were inoculated with the above three microorganisms at a concentration of106-7 cfu/ml. Of the three factors protozoan predation was the major factor (followed by bacteriophages) influencing the mortality of the test organisms. Competition by autochthonous bacterial population had little effect on the test organisms. In cycloheximide treated and non-treated estuarine water, E. coli, S. paratyphi and V.parahaemolyticus showed more robust survival at 20oC than at 30oC.However, no significant (P>0.05) variation in the survival of the test organisms was observed in cycloheximide-treated, non-treated andin microcosm-inoculated with autochthonous bacteria. This information is important in order to understand self-purifying factors and their relative importance in the aquatic environments.