STARVATION RECOVERY OF STAPHYLOCOCCUS-AUREUS-8325-4

Nutrient limitation of Staphylococcus aureus induces a starvation-surv ival state which enables it to survive until sufficient nutrients beco me available to Support growth. The response of starved S. aureus cell s to nutritional upshift was analysed to characterize the recovery mec hanism which results in the resumption of rapid growth. S. aureus 8325 -4 starved for 7 d in a chemically defined medium limited for glucose was able to resume growth upon the addition of complex medium (brain h eart infusion broth) or a mixture of amino acids and glucose. The addi tion of either glucose or amino acids alone did not lead to recovery o f cells. Prior to the first cell division event, a lag period of about 120-150 min was observed, the duration of which was independent of th e length of starvation survival. During this lag period, RNA synthesis increased immediately upon the addition of nutrients whilst protein s ynthesis was delayed by approximately 5 min. Cells rapidly enlarged wi thin 30 min of recovery, and initiation of chromosome replication coul d be detected after 90 min. Changes in the profile of proteins express ed during the recovery period revealed that several starvation-specifi c proteins were downregulated within 30 min, whilst other proteins wer e common to both starvation and recovery. Two proteins were identified which were only transiently expressed during the first 60 min of reco very. Protein synthesis could be detected during recovery even if the cells had been treated with the RNA synthesis inhibitor rifampicin for 30 min prior to the addition of recovery nutrients, demonstrating tha t several proteins are translated from long-lived mRNA transcripts pre sent in starved cells.