Abstract
Bacillus species present a major concern in the dairy industry as they can form biofilms in pipelines and on surfaces of equipment and machinery used in the entire line of production. These biofilms represent a continuous hygienic problem and can lead to serious economic losses due to food spoilage and equipment impairment. Biofilm formation by Bacillus subtilis is apparently dependent on LuxS quorum sensing (QS) by Autoinducer-2 (AI-2). However, the link between sensing environmental cues and AI-2 induced biofilm formation remains largely unknown. The aim of this study is to investigate the role of lactose, the primary sugar in milk, on biofilm formation by B. subtilis and its possible link to QS processes. Our phenotypic analysis shows that lactose induces formation of biofilm bundles as well as formation of colony type biofilm. Furthermore, using reporter strain assays, we observed an increase in AI-2 production by B. subtilis in response to lactose in a dose dependent manner. Moreover, we found that expression of eps and tapA operons, responsible for extracellular matrix synthesis in B. subtilis, were notably up-regulated in response to lactose. Importantly, we also observed that LuxS is essential for B. subtilis biofilm formation in the presence of lactose. Overall, our results suggest that lactose may induce biofilm formation by B. subtilis through the LuxS pathway.
Highlights
Bacteria often use quorum sensing (QS) as cell–cell communication mechanism to control expression of genes that affect a variety of cellular processes (Fuqua et al, 1994; Miller and Bassler, 2001; Bai and Rai, 2011)
We found that addition of lactose to growth media such as Lysogeny broth (LB) or chemical defined agar (CDA) enhances biofilm formation by B. subtilis
We tested whether the increase in biofilm formation in the presence of lactose is due to the increase in bacterial growth rate
Summary
Bacteria often use quorum sensing (QS) as cell–cell communication mechanism to control expression of genes that affect a variety of cellular processes (Fuqua et al, 1994; Miller and Bassler, 2001; Bai and Rai, 2011). QS modulates various cellular processes involved mainly in the regulation of virulence factors, sporulation, motility, toxin production (Hammer and Bassler, 2003; Henke and Bassler, 2004; Smith et al, 2004; Waters and Bassler, 2006) and Lactose Triggers Bacillus subtilis Biofilm Formation formation of a structured multicellular community of bacterial cells, termed biofilm (Hall-Stoodley et al, 2004; Kolter and Greenberg, 2006) It appears that biofilm formation is the most successful strategy for bacteria to survive unfavorable environmental conditions (Stewart and Costerton, 2001; Hall-Stoodley et al, 2004). Bacteria in biofilms are highly resistant to disinfection and antibiotic treatments, biofilm formation is considered as a major problem in the industrial fields and in medicine (Simoes et al, 2010)
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