Flagellar motility plays important role in Biofilm formation of Bacillus cereus and Yersinia enterocolitica

Abstract

Bacteria live either independently as planktonic cells or in organized surface associated colonies called as biofilms. Biofilms play an important role in increased pathogenesis of bacteria and it is assumed that motility is one of the contributing factors towards biofilm initiation. This study was planned to identify the role of flagella in biofilm formation by constructing flagellated (wild type) and physically disrupted variants (non-motile). Total 10 clinical bacterial strains were isolated and characterized. Morphological and biochemical study identified these strains as Enterobacter spp., Pseudomonas spp., Yersinia spp., Escherichia spp., Salmonella spp., Proteus spp., Staphylococcus spp., Streptococcus spp., Lactobacillus spp. and Bacillus spp. Among all strains, two strains including Yersinia spp and Bacillus spp. showed higher antibiotic resistance, hence studied at molecular and physiological level. Biofilm formation capacity of strains was analyzed using three methods including Congo red assay, Test tube assay and Liquid-interface coverslip assay. Afterwards, flagellar disintegration was induced by blending and centrifugation for 5, 10 and 15 minutes. 16S rRNA sequencing showed two strains as Bacillus cereus and Yersinia enterocolitica. Both strains produced significant biofilm by all three above mentioned methods. A motility test of these blended variants showed partial/diminished motility with increased blending time. The significant loss in biofilm formation after 15 minutes blending confirmed the important flagellar contribution to the initiation of biofilm formation. This biofilm defect observed in flagella paralysed/minus variants presumably may be due to defects in attachments to surface at early stages. This study indicated that flagellar motility is crucial initially for surface attachment and subsequently for biofilm formation.