Dynamics in microbial communities: unraveling mechanisms to identify principles

Abstract

Diversity begets higher-order properties such as functional stability and robustness in microbial communities, but principles that inform conceptual (and eventually predictive) models of community dynamics are lacking. Recent work has shown that selection as well as dispersal and drift shape communities, but the mechanistic bases for assembly of communities and the forces that maintain their function in the face of environmental perturbation are not well understood. Conceptually, some interactions among community members could generate endogenous dynamics in composition, even in the absence of environmental changes. These endogenous dynamics are further perturbed by exogenous forcing factors to produce a richer network of community interactions and it is this 'system' that is the basis for higher-order community properties. Elucidation of principles that follow from this conceptual model requires identifying the mechanisms that (a) optimize diversity within a community and (b) impart community stability. The network of interactions between organisms can be an important element by providing a buffer against disturbance beyond the effect of functional redundancy, as alternative pathways with different combinations of microbes can be recruited to fulfill specific functions.

Figure 1

Hypothetical data from a theoretical experiment to identify a community design principle relating community biomass productivity and species diversity (n) to the degree of environmental variation to which the community is exposed. Inset boxes depict communities of varying species diversity. This experimental data would lend support to the following design principle: the optimal species diversity for maximum productivity increases with the degree of variation in environmental conditions that a community experiences.