CULTURABILITY AND EXPRESSION OF OUTER-MEMBRANE PROTEINS DURING CARBON, NITROGEN, OR PHOSPHORUS STARVATION OF PSEUDOMONAS-FLUORESCENS DF57 AND PSEUDOMONAS-PUTIDA DF14

Changes in culturability and outer membrane protein profiles were inve stigated in Pseudomonas fluorescens DF57 and Pseudomonas putida DF14 d uring starvation for carbon, nitrogen, and phosphorus. P. fluorescens DF57 remained fully culturable for 4 days in all starvation regimes. T he cell mass increased during starvation for nitrogen and phosphorus, indicating the accumulation of storage compounds, whereas it decreased slightly in carbon-starved cells. P. putida DF14 lost culturability d uring phosphorus starvation, and the mass of phosphate-starved cells d id not increase. Analysis of additional P. fluorescens and P. putida s trains, however, showed that the ability to preserve culturability dur ing phosphorus starvation was not species but strain dependent. In DF5 7, an outer membrane protein of 55 kDa appeared during starvation for phosphorus, while another protein of 63 kDa was seen during all starva tion conditions. DF14 induced two outer membrane proteins of 28 and 29 kDa during starvation for carbon and nitrogen, but no phosphorus-spec ific starvation protein could be detected. Therefore, starvation-induc ed outer membrane proteins do not seem to be conserved among the fluor escent pseudomonads and a unique starvation response might be found in individual strains.