Two-Component Systems of Corynebacterium glutamicum : Deletion Analysis and Involvement of the PhoS-PhoR System in the Phosphate Starvation Response

Corynebacterium glutamicum contains genes for 13 two-component signal transduction systems. In order to test for their essentiality and involvement in the adaptive response to phosphate (P i ) starvation, a set of 12 deletion mutants was constructed. One of the mutants was specifically impaired in its ability to grow under P i limitation, and therefore the genes lacking in this strain were named phoS (encoding the sensor kinase) and phoR (encoding the response regulator). DNA microarray analyses with the C. glutamicum wild type and the Δ phoRS mutant supported a role for the PhoRS system in the adaptation to P i starvation. In contrast to the wild type, the Δ phoRS mutant did not induce the known P i starvation-inducible ( psi ) genes within 1 hour after a shift from P i excess to P i limitation, except for the pstSCAB operon, which was still partially induced. This indicates an activator function for PhoR and the existence of at least one additional regulator of the pst operon. Primer extension analysis of selected psi genes ( pstS , ugpA , phoR , ushA , and nucH ) confirmed the microarray data and provided evidence for positive autoregulation of the phoRS genes.