Hyperswarming in Bacillus cereus: Tradeoffs against biofilm formation

Sarmah, Hemanta (2014) Hyperswarming in Bacillus cereus: Tradeoffs against biofilm formation. Masters thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

Bacteria have evolved in a manner that they can sustain themselves in some of the most gruesome environments possible. Biofilm formation is a property that enables bacteria to prevail in the form of a community under such stressed conditions. Within a biofilm community there are groups of cells that perform specialized tasks. Bacterial swarming or collective cell movement refers to one of such tasks carried out by certain group of cells – preferably found in the periphery of a biofilm framework – commonly known as hyperswarmers. In this project our aim lies in elucidation of roles played by hyperswarmers in a biofilm mass. Additionally, attempts have been made to compare properties such as growth rate, bio-surfactant production, antibiotic tolerance, biofilm forming ability across a hyperswarming and a non-hyperswarmer. Cell surface physiology was compared using scanning electron microscopy. Putative genes contributing summarily to the phenomena of swarming were analyzed at different time points. Our studies reveal a surge in expression of PlcR - a transcription factor that controls expression of regulon involved in food supply, ion balance, toxin production and cell-cell communication – during early stages of swarming for the hyperswarming strain. Correspondingly the non-hyperswarmer showed negligible expression of PlcR at similar time points. We also attempted to throw light on bacterial mechanotaxis, a method wherein locomotion in bacteria is investigated subject to an incumbent mechanical sheer/stress.

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