Microbial Ecology

, Volume 49, Issue 2, pp 257–264 | Cite as

Effects of Microbial Community Diversity on the Survival of Pseudomonas aeruginosa in the Wheat Rhizosphere



Ecological theory suggests that microbial communities with greater microbial diversity would be less susceptible to invasion by potential opportunistic pathogens. We investigated whether the survival of the opportunistic pathogen Pseudomonas aeruginosa in the wheat rhizosphere would be affected by the presence of natural and constructed microbial communities of various diversity levels. Three levels of microbial community diversity were derived from wheat roots by a dilution/extinction approach. These wheat rhizosphere inocula, as well as a gnotobiotic microbial community consisting of seven culturable wheat rhizobacterial isolates, were introduced into the nutrient solution of hydroponically grown wheat plants on the day of planting. Phenotypic characterization of the culturable microbial communities on R2A medium, Shannon microbial diversity index, community-level physiological profiles, and terminal restriction fragment length polymorphisms were used to assess the varying microbial diversity levels. At day 7 the roots were invaded with P. aeruginosa and the number of P. aeruginosa colony forming units per root were measured at day 14. The average number of surviving P. aeruginosa cells was 3.52, 4.90, 7.18, 6.65 log10 cfu/root in the high, medium, low, and gnotobiotic microbial community diversity level treatments, respectively. The invasibility of the rhizosphere communities by P. aeruginosa was inversely related to the level of diversity from the dilution extinction gradient. The gnotobiotic community did not confer protection against P. aeruginosa invasion. Although these data indicate that invasibility is inversely related to diversity, further study is needed to both reproduce these findings and define the specific mechanisms of the diversity effect.



Pseudomonas aeruginosa UG2Lr was provided by Dr. Jack Trevors, the University of Guelph, Guelph, Ontario, Canada. This research was supported by a Florida Space Grant Consortium Program (FSGCP) grant and Dynamac, Corp (Life Sciences Support Facilities at Cape Canaveral Air Force Station, NASA Kennedy Space Center, FL).


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Copyright information

© Springer Science+Business Media, Inc. 2005

Authors and Affiliations

  1. 1.Department of BiologyUniversity of South FloridaTampaUSA
  2. 2.Institute of Marine and Coastal ScienceRutgers UniversityNew BrunswickUSA
  3. 3.Dynamac CorporationKennedy Space CenterUSA
  4. 4.U.S. Department of Agriculture, Agricultural Research ServiceEastern Regional Research CenterWyndmoor

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