SURVIVAL OF ENTEROCOCCUS-FAECALIS IN AN OLIGOTROPHIC MICROCOSM - CHANGES IN MORPHOLOGY, DEVELOPMENT OF GENERAL STRESS RESISTANCE, AND ANALYSIS OF PROTEIN-SYNTHESIS

The ability of Enterococcus faecalis to metabolically adapt to an olig otrophic environment has been analyzed. E. faecalis is able to survive for prolonged periods under conditions of complete starvation establi shed by incubation in tap water. During incubation in this microcosm, cells developed a rippled cell surface with irregular shapes. Exponent ially growing cells survived to the same extent as cells starved for g lucose prior to exposure to the multiple nutrient deficient stress. Ch loramphenicol treatment during incubation in tap water led to a rapid decline in plate counts for exponentially growing cells but showed pro gressively reduced influence on stationary-phase cells harvested after different times of glucose starvation. During incubation in the oligo trophic environment, cells from the exponential-growth phase and early -stationary phase became progressively more resistant to other environ mental stresses (heat [62 degrees C], acid [pH 3.3], UV254 nm light [1 80 J/m(2)], and sodium hypochlorite [0.05%]) until they reached a maxi mum of survival characteristic for each treatment. In contrast, cells starved of glucose for 24 h did not become more resistant to the diffe rent treatments during incubation in tap mater. Our combined data sugg est that energy starvation induces a response similar to that triggere d by oligotrophy. Analysis of protein synthesis by two-dimensional gel electrophoresis revealed the enhanced synthesis of 51 proteins which mere; induced in the oligotrophic environment. A comparison of these o ligotrophy-inducible proteins with the 42 glucose starvation-induced p olypeptides (J. C. Giard, A. Hartke, S. Flahaut, P. Boutibonnes, and Y . Auffray, Res. Microbiol. 148:27-35, 1997) shelved that 16 are common between the two different starvation conditions. These proteins and t he corresponding genes seem to play a key role in the observed phenome na of long-term survival and development of general stress resistance of starved cultures of E. faecalis.