The response of the marine Vibrio sp. strain S14 to starvation for carbon, nitrogen, or phosphorus and to simultaneous depletion of all these nutrients (multiple-nutrient starvation) was examined with respect to survival, stress resistance, quantitative and qualitative alterations in protein and RNA synthesis, and the induction of the stringent control. Of the conditions tested, carbon starvation and multiple-nutrient starvation both promoted long-term starvation resistance and a rapid induction of the stringent control, as deduced from the kinetics of RNA synthesis. Carbonand multiple-nutrient-starved cells were also found to become increasingly resistant to heat, UV, near-UV, and CdCl2 stress. Nitrogenand phosphorus-starved cells demonstrated a poor ability to survive in the presence of carbon and did not develop a marked resistance to the stresses examined. The carbon, nitrogen, and phosphorus starvation stimulons consisted of about 20 proteins each, while simultaneous starvation for all the nutrients elicited an increased synthesis of 42 polypeptides. Nine common proteins were found to be induced regardless of the starvation condition used and were tentatively termed general starvation proteins. It was also dem'onstrated that the total number of proteins induced in response to multiple-nutrient starvation was not a predictable sum of the different individual starvation stimulons. Multiple-nutrient starvation induced 14 proteins which were not detected at increased levels of expression in response to individual starvation conditions. Furthermore, four out of five phosphorus starvation-specific polypeptides were not induced during simultaneous starvation for phosphorus, nitrogen, and carbon. The results are discussed in light of the physiological alterations previously described for Vibrio sp. strain S14 cells starved for carbon, nitrogen, and phosphorus simultaneously.

We report the cloning, sequencing, and characterization of the rpoE homolog in Vibrio angustum S14. The rpoE gene encodes a protein with a predicted molecular mass of 19.4 kDa and has been demonstrated to be present as a single-copy gene by Southern blot analysis. The deduced amino acid sequence of RpoE is most similar to that of the RpoE homolog of Sphingomonas aromaticivorans, 24 , displaying sequence similarity and identity of 63 and 43%, respectively. Northern blot analysis demonstrated the induction of rpoE 6, 12, and 40 min after a temperature shift to 40°C. An rpoE mutant was constructed by gene disruption. There was no difference in viability during logarithmic growth, stationary phase, or carbon starvation between the wild type and the rpoE mutant strain. In contrast, survival of the mutant was impaired following heat shock during exponential growth, as well as after oxidative stress at 24 h of carbon starvation. The mutant exhibited microcolony formation during optimal growth temperatures (22 to 30°C), and cell area measurements revealed an increase in cell volume of the mutant during growth at 30°C, compared to the wild-type strain. Moreover, outer membrane and periplasmic space protein analysis demonstrated many alterations in the protein profiles for the mutant during growth and carbon starvation, as well as following oxidative stress, in comparison with the wild-type strain. It is thereby concluded that RpoE has an extracytoplasmic function and mediates a range of specific responses in stressed as well as unstressed cells of V. angustum S14.Rapid and efficient adaptation to changes in environmental conditions is required for bacterial replication and survival in natural habitats. The marine bacterium Vibrio angustum S14 produces a highly orchestrated response to starvation and stress conditions, and studies of this organism have provided novel information on adaptive responses (45, 54), including the role of master regulators (11,42,44), extracellular signals (55), and regulation of transcript stability essential for the outgrowth response of starved cells (56). Alternative sigma factors play an important role in regulating the transcription of many genes that are induced during stationary phase, starvation, and stress adaptation (16,58). To examine the role of alternative sigma factors in adaptive responses of V. angustum S14, the identification and characterization of the stress responses mediated by RpoS, the stationary-phase sigma factor, in this organism were sought. By use of an rpoS probe derived from Escherichia coli, several clones from a V. angustum S14 genomic library were isolated. One of these clones encoded another alternative sigma factor, RpoE.Homologs of rpoE encode proteins that are members of the E family, a distinctive subclass of the 70 type of sigma factors (termed extracytoplasmic-function [ECF] factors) (28). In response to the extracellular environment, ECF factors have been found to regulate gene expression in diverse bacterial species. RpoE homologs have been implicated a...