Effect of salt stress on swarming behavior of Bacillus thuringiensis KPWP1

Hiba, Hanan K (2025) Effect of salt stress on swarming behavior of Bacillus thuringiensis KPWP1. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Hiba Hanan K (20MS015)) 20MS015_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

This study investigates the relationship between salt stress and the behaviour of Bacillus thuringiensis KPWP1, specifically examining how increasing NaCl concentrations affect swarming motility and cry protein production. B. thuringiensis is economically significant for its insecticidal properties due to the production of crystalline inclusions containing δ-endotoxins (cry proteins) during sporulation. The study demonstrates that increasing NaCl concentration (from 0.5% to 3%) in growth media significantly reduces swarming motility of B. thuringiensis KPWP1, as evidenced by decreasing colony radius measurements over an eight-day period. Confocal Laser Scanning Microscopy revealed that higher salt concentrations altered cellular arrangement patterns, with cells becoming more compact as NaCl levels increased. Cells in swirling pattern were observed at the periphery of colonies grown in 0.5% NaCl (Control), but this pattern changed with increasing salt stress. Coomassie blue staining showed that cry protein abundance increased when the concentration of salt (NaCl) increased in the growth media. Conversely, at the periphery of colonies, rod-shaped cells predominated with minimal cry protein presence across all salt concentrations. While PCR analysis confirmed the presence of 16S rRNA gene in the isolated genomic DNA of B. thuringiensis KPWP1. These findings support the hypothesis that increased NaCl concentration generates stress that inhibits swarming behaviour while enhancing cry protein production in B. thuringiensis KPWP1, suggesting potential implications for optimizing biopesticide production.

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