The ecology and evolution of social behavior in microbes

Abstract

Cooperation has been studied extensively across the tree of life, from eusociality in insects to social behavior in humans, but it is only recently that a social dimension has been recognized and extensively explored for microbes. Research into microbial cooperation has accelerated dramatically and microbes have become a favorite system because of their fast evolution, their convenience as lab study systems and the opportunity for molecular investigations. However, the study of microbes also poses significant challenges, such as a lack of knowledge and an inaccessibility of the ecological context (used here to include both the abiotic and the biotic environment) under which the trait deemed cooperative has evolved and is maintained. I review the experimental and theoretical evidence in support of the limitations of the study of social behavior in microbes in the absence of an ecological context. I discuss both the need and the opportunities for experimental investigations that can inform a theoretical framework able to reframe the general questions of social behavior in a clear ecological context and to account for eco-evolutionary feedback.

Is “Wolf‐Pack” Predation by Antimicrobial Bacteria Cooperative? Cell Behaviour and Predatory Mechanisms Indicate Profound Selfishness, Even when Working Alongside Kin

“…It is certainly not straightforward to apply the lessons learned from animal cooperativity to microbial systems. Although a thorough treatment of this subject is beyond our word limit, some excellent reviews and discussions are available …”

“…For cooperativity to evolve, there must be a resulting increase in fitness that more than compensates for the cost of cooperative behavior. For microbes, this fitness benefit tends to be equated with increases in growth (or survival) rates when compared with competing noncooperating organisms . As bacterial populations are largely clonal, neighboring cells in a colony will tend to be phenotypically identical/similar, hence precluding cooperation based on the division of labor or discrimination between individuals.…”

“…Care should be taken with all these terms though, as their meanings can be vague and poorly defined, resulting in them being used almost interchangeably. Even in theoretical or animal studies of behavior, there can be confusion with nomenclature and definitions . The use of particular terms can also imply certain features, e.g., “multicellularity” suggests a beneficial regulated biological phenomenon, which may not always be the case.…”

“…Although a thorough treatment of this subject is beyond our word limit, some excellent reviews and discussions are available. [48][49][50][51][52] For cooperativity to evolve, there must be a resulting increase in fitness that more than compensates for the cost of cooperative behavior. For microbes, this fitness benefit tends to be equated with increases in growth (or survival) rates when compared with competing noncooperating organisms.…”

“…For microbes, this fitness benefit tends to be equated with increases in growth (or survival) rates when compared with competing noncooperating organisms. [49] As bacterial populations are largely clonal, neighboring cells in a colony will tend to be phenotypically identical/similar, hence precluding cooperation based on the division of labor or discrimination between individuals. Differentiation into discrete cell types can occur (e.g., during myxobacterial fruiting), and apparent kin discrimination between strains has also been observed.…”