Abstract
Common garden experiments that inoculate a standardised growth medium with synthetic microbial communities (i.e. constructed from individual isolates or using dilution cultures) suggest that the ability of the community to resist invasions by additional microbial taxa can be predicted by the overall community productivity (broadly defined as cumulative cell density and/or growth rate). However, to the best of our knowledge, no common garden study has yet investigated the relationship between microbial community composition and invasion resistance in microcosms whose compositional differences reflect natural, rather than laboratory-designed, variation. We conducted experimental invasions of two bacterial strains (Pseudomonas fluorescens and Pseudomonas putida) into laboratory microcosms inoculated with 680 different mixtures of bacteria derived from naturally occurring microbial communities collected in the field. Using 16S rRNA gene amplicon sequencing to characterise microcosm starting composition, and high-throughput assays of community phenotypes including productivity and invader survival, we determined that productivity is a key predictor of invasion resistance in natural microbial communities, substantially mediating the effect of composition on invasion resistance. The results suggest that similar general principles govern invasion in artificial and natural communities, and that factors affecting resident community productivity should be a focal point for future microbial invasion experiments.
Highlights
Microbial communities of all types are challenged by the arrival of dispersing microbes, which may displace resident taxa and alter ecosystem functioning (Amalfitano et al, 2015; Fernandez-Gonzalez et al, 2020; Kinnunen et al., 2016; Litchman, 2010; Mallon et al, 2015a; Thakur et al, 2019)
Synthetic microbial communities have suggested that community productivity is of such importance to a microbial community’s invasion resistance that it is often the main explanation for the effect of that the composition of the community inoculated into the microcosm has on invasion resistance (Eisenhauer et al, 2013; Hodgson et al, 2002; van Elsas et al, 2012; Yang et al, 2018)
Microcosms containing a sterile culture medium are inoculated artificial microbial communities constructed from different combinations of culturable taxa and/or dilutions of natural communities. Each of these communities - differing in their composition - is invaded with the same population of microbes to assess the relationship between community composition, productivity and invasion resistance
Summary
Microbial communities of all types are challenged by the arrival of dispersing microbes, which may displace resident taxa and alter ecosystem functioning (Amalfitano et al, 2015; Fernandez-Gonzalez et al, 2020; Kinnunen et al., 2016; Litchman, 2010; Mallon et al, 2015a; Thakur et al, 2019). Synthetic microbial communities have suggested that community productivity is of such importance to a microbial community’s invasion resistance that it is often the main explanation for the effect of that the composition of the community inoculated into the microcosm has on invasion resistance (Eisenhauer et al., 2013; Hodgson et al, 2002; van Elsas et al, 2012; Yang et al, 2018) In these studies, microcosms containing a sterile culture medium (e.g. lab broth, autoclaved soil) are inoculated artificial microbial communities constructed from different combinations of culturable taxa and/or dilutions of natural communities (typically 90% at each dilutions step). Since higher-diversity communities are generally more productive (Bell et al, 2005b), there is often a negative relationship between a resident community’s diversity and invasibility (e.g. Hodgson et al, 2002)
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