Role in cell permeability of an essential two-component system in Staphylococcus aureus

A temperature-sensitive lethal mutant of Staphylococcus aureus was found to harbor a mutation In the uncharacterized two-component histidine kinase (H K)-response regulator (RR) pair encoded by yycFG; orthologues of yycFG coul d be identified in the genomes of Bacillus subtilis and other gram-positive bacteria, Sequence analysis of the mutant revealed a point mutation result ing in a nonconservative change (Glu to Lys) in the regulator domain of the RR at position 63, To confirm that this signal transduction system was ess ential, a disrupted copy of either the RR (yycF) or the HK (yycG) was const ructed with a set of suicide vectors and used to generate tandem duplicatio ns in the chromosome, Resolution of the duplications, leaving: an insertion in either the yycF or the yycG coding region, was achieved only in the pre sence of an additional wild-type copy of the two open reading frames. Pheno typic characterization of the conditional lethal mutant showed that at perm issive growth conditions, the mutant was hypersusceptible to macrolide and lincosamide antibiotics, even in the presence of the ermB resistance determ inant, Other mutant phenotypes, including hypersensitivity to unsaturated l ong-chain fatty acids and suppression of the conditional lethal phenotype b y high sucrose and NaCl concentrations, suggest that the role of the two-co mponent system includes the proper regulation of bacterial cell wall or mem brane composition. The effects of this point mutation are strongly bacteric idal at the nonpermissive temperature, indicating that this pathway provide s an excellent target for the identification of novel antibiotics.