Cooperation and the evolutionary ecology of bacterial virulence: TheBacillus cereusgroup as a novel study system

Abstract

How significant is social evolution theory for the maintenance of virulence in natural populations? We assume that secreted, distantly acting virulence factors are highly likely to be cooperative public goods. Using this assumption, we discuss and critically assess the potential importance of social interactions for understanding the evolution, diversity and distribution of virulence in the Bacillus cereus group, a novel study system for microbial social biology. We conclude that dynamic equilibria in Cry toxin production, as well as strong spatial structure and population bottlenecks in hosts are the main ecological factors maintaining the cooperative secretion of virulence factors and argue that collective action has contributed to the evolution of narrow host range. Non-linearities in the benefits associated with public goods, as well as the lack of private secretion systems in the Firmicutes may also explain the prevalence and importance of distantly acting virulence factors in B. cereus and its relatives.

The Genomes, Proteomes, and Structures of Three Novel Phages That Infect the Bacillus cereus Group and Carry Putative Virulence Factors

“…These results are consistent with the highly related nature of the B. cereus, B. anthracis, and B. thuringiensis species (14,15,52). In addition to host range, superinfection studies were performed in order to assess whether the phages were strictly lytic or temperate.…”

Outer Membrane Vesicles (OMVs) of Gram-negative Bacteria: A Perspective Update

“…In comparison with the the individual survival traits with few interactions and no compartmentalization (Manning and Kuehn, 2013), a different group of bacteria has emerged with survival strategies similar to the eukaryotes (Raymond and Bonsall, 2013; Spitzer and Poolman, 2013). With ordered structural organization, fine-tuned physiology, and interactive social behavior, a paradigm shift for better survival is observed in bacteria.…”

Division of labour and terminal differentiation in a novel Bacillus thuringiensis strain

“…The PlcR-PapR and NprR-NprX systems (Perchat et al, 2011) of LM1212 were found identical to those of the anthrax-casing B. cereus G9241, although it contained no anthrax toxin genes and did not produce a capsule. Broadly, strains in the anthrax clade are more likely to be associated with vertebrate hosts, whereas most entomopathogenic Bt strains fall into a different clade (Raymond and Bonsall, 2013b). The natural host affiliations of Bt strains in the anthrax clade are almost entirely unknown and so it was not surprising that we were unable to identify an invertebrate host.…”

“…These species names do not represent good monophyletic groups, so it is difficult to distinguish them using chromosomal genetic typing methods (Helgason et al, 2000;Vilas-Boas et al, 2007;Raymond et al, 2010a). However, phylogenetic analysis of strains characterized by multiple locus sequence typing suggests that closely related strains are likely to have similar ecology or host association (Guinebretière et al, 2010;Raymond et al, 2010b;Raymond and Bonsall, 2013a). In this study, we identified LM1212 as a strain of Bt, based on both genetic typing methods (Supplementary Figure S3; Supplementary Table S3) and phenotypic identification (Figures 1b and 2; Supplementary Figures S2A and B).…”