Ecological drivers of division of labour in Streptomyces

Abstract

Division of labour occurs when different individuals, cells or tissues become specialised to perform complementary tasks that benefit the whole organism or social group. Although long studied in multicellular organisms and colonies of social insects, several recent studies have established that division of labour is common in microorganisms. We review recent work on the division of labour in unicellular and multicellular bacteria, with a particular focus on reproductive and metabolic divisions of labour in actinomycetes. Actinomycetes show enormous variation in sporophore morphology and spore production patterns that likely affect the potential for cooperative interactions within colonies. They also display both irreversible genetic and spatiotemporally regulated phenotypic divisions of labour that structure antibiotic production. We highlight outstanding questions in this group of multicellular bacteria and outline factors that can modify the expression of division of labour across microbes.

Figure 1.. Phylogenetic mapping of reproductive divisions of labor in Actinomycetes.

A whole genome phylogeny was produced using the SpeciesTree application in KBase with Bacillus amyloliquefaciens as an outgroup and plotted using the Interactive Tree of Life online suite. The potential to produce motile spores was assessed via BLAST searches for flagellin and the flagellar hook protein FlgK from Actinoplanes missouriensis, a species with well-known ability to produce motile spores (73). Sporophore morphology is described in(73). SEM images were used with permission from the following sources, listed clockwise starting from Kineosporia: (–82).

Figure 2.. Antibiotic divisions of labor in Streptomyces coelicolor.

A. Genetic division of labor due to chromosome deletions. Diverse progeny of a single colony vary in antibiotic production and colony morphology. B. Spatiotemporal divisions of labor within S. coelicolor colonies. EGFP production is driven by the redZ promoter involved in antibiotic production (i.e. undecylprodigiosin production). mCHerry production is driven by the bldN promoter which is involved in production of aerial hyphae. The image in B was reproduced from (41), in accordance with Creative Commons Attribution guidelines.

Figure 3.. Interspecies interactions can promote division of labour and specialized cell types.

A. Pigmented antibiotic induction in S. coelicolor (seen in red) during interspecies interaction with Streptomyces SPB78. B. Induction of antibiotic production in S. tanashiensis by S. griseus. Antibiotic production is seen as a halo of growth inhibition in an overlay of Bacillus subtilis. Images from(64), used with permission. C. Induction of “explorer cells” in S. venezuelae by Saccharomyces cerevisiae. The explorer phenotype is seen as a massive expansion of the S. venezuelae colony in the image at right. Both images were taken after 11 days of growth. Images from(65) are used in accordance with Creative Commons Attribution guidelines.