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Title: Nutrient use preferences among soil Streptomyces suggest greater resource competition in monoculture than polyculture plant communities

item ESSAROUI, ADIL - University Of Minnesota
item Kistler, Harold
item KINKEL, LINDA - University Of Massachusetts

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2016
Publication Date: 6/28/2016
Citation: Essaroui, A., Kistler, H.C., Kinkel, L.L. 2016. Nutrient use preferences among soil Streptomyces suggest greater resource competition in monoculture than polyculture plant communities. Plant and Soil. 405(720):1-15. doi: 10.1007/s11104-016-2968-0.

Interpretive Summary: America's native prairies are composed of a thriving community of perennial herbaceous plants, despite the presence of diverse plant pathogens. How are these communities able to evade significant disease? Are there important lessons that can be applied to agriculture to create healthier, more productive plants? This study evaluates a genus of soil bacteria found in native prairie systems, Streptomyces, vital in the fight against plant pathogens. These bacteria, which are found naturally within the soil, are effective in suppressing plant pathogens since they produce antibiotic compounds when competing for food in highly competitive soils. This study increases understanding of how Streptomyces within the complex microbial community may compete with other members of the community. This information may be used by agronomists to improve plant productivity by providing a robust foundation for understanding the impacts of agronomic practices on soil communities, and in doing so may help harness the benefits of the indigenous microbial community to make agricultural crops more productive.

Technical Abstract: Nutrient use overlap among sympatric Streptomyces populations is correlated with pathogen inhibitory capacity, yet there is little information on either the factors that influence nutrient use overlap among coexisting populations or the diversity of nutrient use among soil Streptomyces. We examined the effects of plant host and plant species richness on nutrient use of Streptomyces isolated from the rhizosphere of Andropogon gerardii (Ag) and Lespedeza capitata (Lc) growing in communities of 1 (monoculture) or 16 (polyculture) plant species. Thirty Streptomyces were isolated from each plant host-plant richness combination, for a total of 120 isolates, and their growth on 95 carbon sources was assessed over 5 days using Biolog SF-P2 plates. Streptomyces nutrient use profiles were characterized and the effects of plant host and plant community richness on nutrient competition and nutrient preferences were determined. Streptomyces grew on a wide range of carbon substrates including labile and recalcitrant substrates, and displayed highly diverse nutrient use profiles. Cumulative growth (growth summed over all nutrients) was significantly greater for isolates from polyculture than from monoculture, and for isolates from Lc vs. Ag. Streptomyces isolates from monocultures, but not polycultures, exhibited a dramatic drop in growth rates between 24 and 72 h post-inoculation, suggesting resource allocation to non-growth functions. Isolates from plots with high soil carbon (polyculture) or high nitrogen (Lc) had larger niche widths than isolates from low C (monocultures) or low N (Ag) soils. Despite their larger niche widths, sympatric Streptomyces isolates from polycultures were significantly more differentiated from one another in preferred nutrients for growth than sympatric isolates from monocultures. These suggest that Streptomyces populations respond to selection imposed by plant host and plant community richness. Moreover, these results are consistent with the hypothesis that responses to resource competition among Streptomyces populations differ in polyculture vs. monoculture plant communities, and specifically that populations from polyculture but not from monoculture mediate resource competition via niche differentiation.