Deletion analysis of RcsC reveals a novel signalling pathway controlling poly-N-acetylglucosamine synthesis and biofilm formation in Escherichia coli.

RcsC is a hybrid histidine kinase that forms part of a phospho-relay signal transduction pathway with RcsD and RcsB. Besides the typical domains of a sensor kinase, i.e. the periplasmic (P), linker (L), dimerization and H-containing (A), and ATP-binding (B) domains, RcsC possesses a receiver domain (D) at the carboxy-terminal domain. To study the role played by each of the RcsC domains, four plasmids containing several of these domains were constructed (PLAB, LAB, AB and ABD) and transformed into Escherichia coli K-12 strain BW25113. Different amounts of biofilm were produced, depending on the RcsC domains expressed: the plasmid expressing the ABD subdomains produced the highest amount of biofilm. This phenotype was also observed when the plasmids were transformed in a ΔrcsCDB strain. Biofilm formation was abolished in the pgaABCD and nhaR backgrounds. The results indicate the existence of a novel signalling pathway that depends on RcsC, yet independent of RcsD and RcsB, that activates the pgaABCD operon and, as a consequence, biofilm formation. This signalling pathway involves the secondary metabolite acetyl phosphate and the response regulator OmpR.