The persistence of bioluminescent Rhizobium meliloti strains L1 (RecA-) and L33 (RecA+) in non-sterile microcosms depends on the soil type, on the co-cultivation of the host legume alfalfa and on the presence of an indigenous R. meliloti population.

摘要

In comparative analyses the influence of soil type, the rhizosphere of plants and the presence of an indigenous R. meliloti population on the population dynamics of bioluminescent R. meliloti strains L1 (RecA-) and L33 (RecA+) was assessed in microcosm studies. Both strains established better in a loamy and a clayey soil than a sandy soil. RecA- strain L1 showed a slightly but statistically significant reduced survival ability compared with RecA+ strain L33 (p ?0.05). The presence of the host plant alfalfa (Medicago sativa) stimulated the growth of both strains in non-sterile soil and no differences in survival between strains were observed. Co-cultivation of clover (Trifolium pratense) or wheat (Triticum aestivum) plants did not affect the survival of either strain. The most pronounced effect on the survival of both strains was exerted by the presence of an indigenous R. meliloti population. RecA- strain L1 showed a significantly impaired survival compared with RecA+ strain L33 (p ?0.002). Moreover, no growth stimulation of strains L1 and L33 by the presence of the host plant alfalfa could be observed. These results indicate that the recA mutation affects the long-term rather than the short-term persistence of R. meliloti after environmentalrelease.