Social evolution in multispecies biofilms

Abstract

Microbial ecology is revealing the vast diversity of strains and species that coexist in many environments, ranging from free-living communities to the symbionts that compose the human microbiome. In parallel, there is growing evidence of the importance of cooperative phenotypes for the growth and behavior of microbial groups. Here we ask: How does the presence of multiple species affect the evolution of cooperative secretions? We use a computer simulation of spatially structured cellular groups that captures key features of their biology and physical environment. When nutrient competition is strong, we find that the addition of new species can inhibit cooperation by eradicating secreting strains before they can become established. When nutrients are abundant and many species mix in one environment, however, our model predicts that secretor strains of any one species will be surrounded by other species. This "social insulation" protects secretors from competition with nonsecretors of the same species and can improve the prospects of within-species cooperation. We also observe constraints on the evolution of mutualistic interactions among species, because it is difficult to find conditions that simultaneously favor both withinand among-species cooperation. Although relatively simple, our model reveals the richness of interactions between the ecology and social evolution of multispecies microbial groups, which can be critical for the evolution of cooperation.mutualism | microbe | spatial organization | extracellular secretion | interspecies

Extracellular matrix structure governs invasion resistance in bacterial biofilms

“…Previous work has identified patterns of inter-and intra-generic cell aggregation that determine a characteristic order of addition of species to microbial communities on teeth after cleaning. The observation of co-aggregation partnerships may indicate instances of mutualism in which both members of the pair benefit from close spatial association (Mitri et al, 2011). However, it is also possible that different bacterial species are simply adapted to bind and subsequently outcompete resident biofilms in communities that have a consistent sequence of occupant eco-types, analogous to competition between late-successional and early-successional species in patches of disturbed forest (Guariguata and Ostertag, 2001).…”

The role of quorum sensing signalling in EPS production and the assembly of a sludge community into aerobic granules

“…This is in contrast to their planktonic single species population counterparts commonly studied in laboratory conditions. The formation and dispersal of structured bacterial biofilms or aggregates occur in response to a range of environmental cues and signals, such as changes in nutrient concentrations, oxygen, temperature, as well as chemicals and predatory stresses (Bassler et al, 1993;Matz et al, 2004;McDougald et al, 2011;Mitri et al, 2011). In many cases, the signal transduction pathways, the associated changes in gene expression and the involvement of second messenger systems have also begun to be unravelled (Barraud et al, 2009;Petrova and Sauer, 2012).…”

Selection methods regulate evolution of cooperation in digital evolution

“…While all five selection methods are frequently used to simulate differential selection (PSM in [19][20][21][22][23][24][25][26][27][28][29][30][31][32]; RSM in [33,34]; TPSM in [35][36][37]; TUSM in [38][39][40][41][42][43][44][45][46], TSM in [22,47,48]), the choice between them is rarely justified. Moreover, little attempt has been made to quantify the effects of selection methods on the dynamics of the digital evolution (but see [22,49]).…”

“…To address this problem, we investigate theoretically and with numerical experiments how the five selection methods regulate the evolution of cooperation. We focus on cooperation, because digital evolution is especially popular in this domain [19][20][21][22][23][24][26][27][28][29]33,38,41,47,48,54,55], and it is an important biological phenomenon that has attracted extensive scientific interest (see [56][57][58][59][60] for reviews). We consider a population of related individuals, each having a genotype that consists of a haploid allele encoding for cooperation or defection.…”