Synthesis of immediate upshift (Iup) proteins during recovery of marine Vibrio sp. strain S14 subjected to long-term carbon starvation

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Abstract
Proteins induced during the initial phase of recovery after long-term carbon starvation in the marine Vibrio sp. strain S14 were identified by two-dimensional gel electrophoresis analysis. Nutritional upshift experiments with pulse-labeled cells were performed after addition of glucose to cells starved for 48 h. Eighteen proteins synthesized during the first 3 min after substrate addition were identified and designated immediate upshift proteins (Iup proteins). They were induced at least 10-fold compared with the rate of synthesis during starvation. Of the Iup proteins, five are not found in exponentially growing cells. Subsequent to the first 3 min of glucose addition, a complex pattern of sequential synthesis of proteins made during a transient phase as well as proteins made during 60 min of the outgrowth response was monitored. To resolve whether the Iup proteins were synthesized from stable transcripts, the initiation of transcription was inhibited by rifampin (Rif). Addition of Rif 5 min prior to glucose promoted upshift resulted in the synthesis of 12 Iup proteins. Furthermore, three Iup proteins were still induced by cells that were Rif treated 20 min prior to the upshift. These results suggest that stable but silent transcripts exist during starvation and that the translation of these mRNA species is initiated by substrate addition. This regulatory mechanism may be essential for an immediate initiation of the recovery program by the nongrowing cell.