A Flagella Hook Coding Gene flgE Positively Affects Biofilm Formation and Cereulide Production in Emetic Bacillus cereus

Abstract

<i>Bacillus cereus</i>, an important foodborne pathogen, poses a risk to food safety and quality. Robust biofilm formation ability is one of the key properties that is responsible for the food contamination and food poisoning caused by <i>B. cereus</i>, especially the emetic strains. To investigate the mechanism of biofilm formation in emetic <i>B</i>. <i>cereus</i> strains, we screened for the mutants that fail to form biofilms by using random mutagenesis toward <i>B. cereus</i> 892-1, an emetic strain with strong biofilm formation ability. When knocking out <i>flgE</i>, a flagellar hook encoding gene, the mutant showed disappearance of flagellar structure and swimming ability. Further analysis revealed that both pellicle and ring presented defects in the null mutant compared with the wild-type and complementary strains. Compared with the flagellar paralytic strains <b>Δ</b> <i>motA</i> and <b>Δ</b> <i>motB</i>, the inhibition of biofilm formation by <b>Δ</b> <i>flgE</i> is not only caused by the inhibition of motility. Interestingly, <b>Δ</b> <i>flgE</i> also decreased the synthesis of cereulide. To our knowledge, this is the first report showing that a flagellar component can both affect the biofilm formation and cereulide production in emetic <i>B. cereus</i>, which can be used as the target to control the biohazard of emetic <i>B. cereus</i>.