ISOLATION AND CHARACTERIZATION OF STAPHYLOCOCCUS-AUREUS STARVATION-INDUCED, STATIONARY-PHASE MUTANTS DEFECTIVE IN SURVIVAL OR RECOVERY

Staphylococcus aureus mutants, defective in the starvation-induced sta tionary phase of growth were isolated from two independent Tn917-LTV1 transposon insertion libraries and were designated suv as they had app arent survival defects. Seven of these mutants were defective under am ino-acid-limiting conditions alone. Two mutants (suv-3 and suv-20) dem onstrated lower plating efficiency when starved for glucose, phosphate or amino acids and one mutant (suv-11) had reduced plating efficiency after amino acid or glucose starvation. All of the mutants tested wer e as resistant to hydrogen peroxide assault as the parent, but six wer e more sensitive to low ph conditions. All the mutants were physically mapped on the S. aureus chromosome using PFGE. Chromosomal DNA flanki ng the Tn917-LTV1 insertion sites was rescued by cloning into Escheric hia coli. DNA sequence analysis resulted in the identification of a nu mber of transposon-disrupted ORFs encoding putative components such as superoxide dismutase (suv-1), haem A synthase (suv-3), a component of the SOS response (suv-9) and hypoxanthine-guanine phosphoribosyltrans ferase (suv-20). The Tn917-LTV1 insertion created lacZ transcriptional fusions for some of the stationary-phase loci. Expression analysis in dicated that suv-4 was induced at mid-exponential phase, whereas suv-3 and suv-11 were induced at the onset of stationary phase. The possibl e roles of these suv components in stationary-phase survival or recove ry is discussed.