Role of <i>bpfA</i> in adhesion and biofilm formation of <i>Shewanella putrefaciens</i> CN32 under cold stress: a comprehensive transcriptomic analysis

As a specific spoilage organism of seafood under refrigerated temperature conditions, <em>Shewanella </em>spp. tend to form biofilms that exacerbate the occurrence of seafood spoilage. Biofilm-promoting factor A (BpfA) has been reported to promote the adhesion and biofilm formation of <em>Shewanella </em>spp., but its role in adhesion and biofilm formation of <em>S. putrefaciens</em><em> </em>under cold stress needs to be further investigated. To better comprehend the effect of BpfA on adhesion and biofilm formation of <em>S</em><em>. putrefaciens </em>under cold stress (4^oC), bacterial adhesion and biofilm phenotype of <em>S. putrefaciens</em> CN32 WT and Δ<em>bpfA</em><em> </em>at 4^oC were analyzed and performed transcriptomics. The results showed that the deletion of <em>bpfA </em>had almost no effect on the growth of <em>S. putrefaciens</em> CN32 at 4^oC, but weakened the unicellular adhesion capacity of <em>S. putrefaciens</em> CN32 and destabilized the stability of the multicellular adhesion layer. In addition, the biomass of the mature biofilm formed by Δ<em>bpfA</em> was merely around 50% of that observed in the mature biofilm of <em>S. putrefaciens</em> CN32 WT, the average thickness and volume of the biofilm decreased by 3% and 8%, respectively, and the composition of the biofilm changed. Transcriptome analysis demonstrated that the deletion of <em>bpfA</em> led to differential expression of genes involved in metabolic pathways such as bacterial chemotaxis, two-component system, tyrosine metabolism, drug metabolism-other enzymes and biofilm formation-<em>Vibrio cholerae, </em>which in turn influenced bacterial adhesion and biofilm formation. Those results advance our acknowledge of the character of BpfA on adhesion and biofilm formation of <em>S. putrefaciens</em> CN32, which contributes to understand bacterial adhesion and the control of biofilm formation.