Formation of a constructed microbial community in a nutrient-rich environment indicates bacterial interspecific competition

Jia Wang, Manasa R. Appidi, Leah H. Burdick, Paul E. Abraham, Robert L. Hettich, Dale A. Pelletier, Mitchel J. Doktycz

March 24, 2024, mSystems; DOI:10.1128/msystems.00006-24

Abstract

Understanding the organizational principles of microbial communities is essential for interpreting ecosystem stability. Previous studies have investigated the formation of bacterial communities under nutrient-poor conditions or obligate relationships to observe cooperative interactions among different species. How microorganisms form stabilized communities in nutrient-rich environments, without obligate metabolic interdependency for growth, is still not fully disclosed. In this study, three bacterial strains isolated from the Populus deltoides rhizosphere were co-cultured in complex medium, and their growth behavior was tracked. These strains co-exist in mixed culture over serial transfer for multiple growth-dilution cycles. Competition is proposed as an emergent interaction relationship among the three bacteria based on their significantly decreased growth levels. The effects of different initial inoculum ratios, up to three orders of magnitude, on community structure were investigated, and the final compositions of the mixed communities with various starting composition indicate that community structure is not dependent on the initial inoculum ratio. Furthermore, the competitive relationships within the community were not altered by different initial inoculum ratios. The community structure was simulated by generalized Lotka-Volterra and dynamic flux balance analysis to provide mechanistic predictions into emergence of community structure under a nutrient-rich environment. Metaproteomic analyses provide support for the metabolite exchanges predicted by computational modeling and for highly altered physiologies when microbes are grown in co-culture. These findings broaden our understanding of bacterial community dynamics and metabolic diversity in higher-order interactions and could be significant in the management of rhizospheric bacterial communities.

Citation

Wang J, Appidi MR, Burdick LH, Abraham PE, Hettich RL, Pelletier DA, Doktycz MJ. Formation of a Constructed Microbial Community in a Nutrient-Rich Environment Indicates Bacterial Interspecific Competition. mSystems 0:e00006-24. DOI:10.1128/msystems.00006-24