Reduced survival of a RecA-deficient Sinorhizobium meliloti strain in sterile and non-sterile soil during heat stress

Greenhouse experiments revealed a reduced viability of a RecA(-) Sinorhizob ium meliloti strain in non-sterile soil during a heat period compared with an isogenic RecA(+) strain. The higher sensitivity to heal stress of the S. meliloti RecA(-) strain was demonstrated during short- and long-term heat stress experiments under controlled conditions in a growth cabinet using di fferent microcosm systems. Live/dead staining of the rhizobial cells showed that the increased sensitivity to heat stress of the RecA(-) S. meliloti s train was due to its higher mortality compared to the isogenic RecA(+) stra in. These results demonstrate for the first time the importance of the recA function for survival of S. meliloti under heat stress conditions in soil. (C) 1998 Federation of European Microbiological Societies. Published by El sevier Science B.V. All rights reserved.