Studies on Inter- and Intraspecific Interactions in Soil Dwelling Hydrocarbon Degrading Bacteria

Chakraborty, Brinta (2014) Studies on Inter- and Intraspecific Interactions in Soil Dwelling Hydrocarbon Degrading Bacteria. PhD thesis, Indian Institute of Science Education and Research (IISER) Kolkata.

PDF (PhD thesis of Brinta Chakraborty) Final_thesis_Brinta.pdf - Submitted Version Restricted to Repository staff only Download (10MB)

Abstract

The principal objective of the present dissertation was to study the intrinsic interaction in bacterial world that governs the dynamicity of the ecosystem and to decipher the secret behind the communication between co-existing bacterial species, which were primarily thriving in a same niche. For that we have had two main propositions (a) to isolate bacterial consortia from a particular source and (b) to study the mechanism of their communication. The result of the present study involves isolation and characterization of naturally occurring used engine oil degrading bacterial species which were thriving in the soil of a service station at Salt Lake, near Kolkata. This signifies that used engine oil degrading bacterial species are evolved to survive in presence of complex carbon sources such as used engine oil (long chain hydrocarbons). The result implies that these bacterial isolates are not obligatory on hydrocarbon sources for their growth and survival. Since hydrocarbon is not being an obligatory carbon source for them, studies on their inter-dependent behavior were done in nutrient abundant condition in liquid as well as semi solid agar media to mimic its natural environment. This outcome could be a result of either differential resource exploitation and/or direct/ indirect interference on each other or both. Results of the present study clearly indicate that the observed interspecific interaction is an obvious evidence of competitive co-existence of Bacillus cereus and Pseudomonas sp. Whereas, for the observed intraspecific interaction in Bacillus cereus, inhibition of quorum sensing genes are responsible for decreased movement of flagella and therefore cells of Bacillus cereus colony stop moving towards its sibling colony. Since, both of the isolated strains of Pseudomonas sp. MSM-M1 and Bacillus cereus MSM-S1 have the potential to degrade used engine oil, the studies of their interactions will contribute towards understanding the potential of bacteria for the process of bioremediation.

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