Bacillus polymyxa stimulates increased Rhizobium e

Authors: Petersen Daniel J Srinivasan Murali Chanway Chris P

Publish Date: 1996/09/01

Volume: 142, Issue: 2-3, Pages: 271-276

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Abstract

Daniel J Petersen Murali Srinivasan Chris P Chanway Bacillus polymyxa stimulates increased Rhizobium etli populations and nodulation when coresident in the rhizosphere of Phaseolus vulgaris FEMS Microbiology Letters Volume 142 Issue 23 September 1996 Pages 271–276 https//doiorg/101111/j157469681996tb08442xMicrobial competition for carbon sources is a primary determinant of rhizosphere ecology We employed the PCR to examine the population fluctuations of a symbiotic nitrogenfixing bacterium Rhizobium etli during the first 11 days following inoculation of Phaseolus vulgaris seedlings grown in the presence or absence of a common asymbiotic rhizosphere resident Bacillus polymyxa When B polymyxa was applied as a coinoculant increases in both early rhizobial root populations and final root population densities were observed as compared to single inoculation with R etli Modifications to host plant growth including increased lateral root formation and nodules number were found concomitant with elevations in R etli populations on plants coinoculated with both bacterial genera In contrast to the in planta results population enhancements were not observed when R etli and B polymyxa were cocultured in vitro using minimal media in the absence of the seedling Addition of seed exudate to the growth media also failed to stimulate the population increases observed during corelease in planta These results suggest that B polymyxa acts indirectly ie via the plant host to increase R etli populations Our observed synergism among coresident bacteria supports the hypothesis that microbial communities which colonize the spermosphere may play a significant role in plant development and rhizosphere ecology

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