Sub-minimum Inhibitory Concentration of Streptomycin and Cephaloridine-
Induced Capsular Polysaccharide Production in Escherichia coli K-12 Increases Biofilm Formation in a Wzy-transporter Dependent Manner

Biofilms are bacterial communities that adhere and endure on solid surfaces. They are known to contribute to antibiotic resistance and disease. In our study, we focused on the relationship between capsule and biofilm formation. cpsB is a gene that encodes an enzyme required for the synthesis of colanic acid, a major component of capsular polysaccharides. The Wzy-system, a membrane transporter encoded by the genes wza-wzb-wzc, is essential for surface expression of capsule. We investigated the role of the cpsB gene and Wzy-transporter genes in capsule production and biofilm formation. Sub-minimum inhibitory concentrations of streptomycin and cephaloridine were used to induce capsule formation in Escherichia coli K-12 wildtype, mutants Δwza, ΔcpsB, and the strain CWG655, lacking the gene cluster wza-wzb-wzc. Biofilm biomass was assessed in the presence of different levels of capsule induced by sub-minimum inhibitory concentration antibiotic treatment. We observed that sub-minimum inhibitory concentration-induced capsule production is important for biofilm formation. Increased capsule production in Escherichia coli K-12 wildtype induced by sub-minimum inhibitory concentration of streptomycin and cephaloridine correlated with an increase in the amount of biofilm detected. Additionally, we show that the mass of the biofilm is related to genes encoding protein related to the Wzy-transport system.