Huang Ying and his team have made new progress in the study of Streptomyces speciation mechanism
Streptomycetes is a group of Gram-positive bacteria with a fungus-like differentiation process that originated about 380 million years ago.Streptomyces are known for producing a rich variety of antibiotics, and are widely distributed in a variety of habitats, with important ecological functions.With the research on its application value and ecological function, a large number of Streptomyces species have been reported.With nearly 700 validly published and correctly named species, Streptomyces is the genus with the largest number of effective species among prokaryotes.How did such a high diversity of species come about?The external factors driving the formation of microbial diversity are mainly geographical and ecological, and different microorganisms may have different patterns.Existing studies believed that the diversity pattern of Streptomyces was similar to animals and plants in the latitudinal gradient model, but the research was limited to the same type of soil in North America, and the genetic differentiation level among strains was already high.So what is the role of ecology in Streptomyces speciation?What are the main forces driving Streptomyces speciation on a global geographic and ecological scale?In order to solve these problems, huang Ying team of institute of Microbiology, Chinese Academy of Sciences conducted a systematic study on the ecological evolution of Streptomyces.We have revealed the habitat barriers of intraspecies gene exchange in Streptomyces (Appl Environ Microbiol, 2015) and the reticular evolution of Streptomyces (Mol Phylogenet Evol, 2016).We also confirmed that habitat adaptation promoted the formation of Streptomyces albidoflavus population structure through population genomics studies (Appl Environ Microbiol, 2019), calling for attention to the role of habitat in the evolution of Streptomyces.Recently, the team published the results of another Streptomyces species study in mBio, which further elucidated the mechanism of Streptomyces speciation.The study collected Streptomyces Olivaceus strains from different habitats (soil, ocean, insects) and continents/oceans and found that although these strains are highly similar at the phenotypic and genomic levels, they still form a distinct population structure that can be divided into two evolutionary lineages.It is well matched to habitat and geographical location.There were gene exchange barriers between lineages, but the gene exchange between strains was not limited by geographical distance, so it was speculated that habitat barriers were the main reason for lineage differentiation.Further comparative genomics revealed that there were multiple lineage-specific genes or gene clusters that were significantly associated with habitat, mainly involved in regulation, resource use and secondary metabolism.Finally, physiological experiments confirmed the fitness tradeoff between the two lineages under different nutrient resources (iron, carbon, etc.) rather than temperature, and the fitness difference between the lineages was highly consistent with the distribution of related functional genes.The results showed that habitat adaptation processes, rather than geographical distance or latitude differences, significantly drove genetic differentiation among closely related Streptomyces, preventing them from spreading and colonizing across habitats, thus impeding gene exchange between them and ultimately leading to the formation of new species.Streptomyces olivacis consists of two newly differentiated cryptic species.These results provide new insights into the formation mechanism of Streptomyces diversity and the concept of species.In this study, Habitat adaptation drives speciation of a Streptomyces species with distinct Habitats and disparate geographicOrigins “, published in the Journal mBio (DOI: 10.1128/ mbio-02781-21).Wang Jiao, Ph.D., State Key Laboratory of Microbial Resources Development, Institute of Microbiology, Chinese Academy of Sciences, is the first author, and Huang Ying is the corresponding author. Professor Pinto-Tomas, University of Costa Rica, is one of the co-authors.The research was supported by the National Natural Science Foundation of China and China Ocean Mineral Resources Research and Development Association.Figure 1 the original link: https://doi.org/10.1128/mBio.02781-21.Figure 2. Phylogenetic tree (A), geographic distribution (B) and population structure (C) of Streptomyces olivacis.Gene exchange within and between Streptomyces olivacis lineages A, gene flow network structure identified by PopCOGenT, the line represents gene flow between genomes;B, fastGEAR identified core genome recombination schematic, black arrow for recent recombination events, red arrow for ancestral recombination events, number for total length of base pairs (and number of recombination events) in recombination region.Figure 3. Genetic structure of chromosome region where representative genes (clusters) related to ecological differentiation (A), sialic acid catabolism gene cluster;B, siderophores synthesis and transport gene clusters;C, glycosidase gene cluster and starch catabolism gene cluster;D, thiopeptide antibiotic gene cluster;E, T1PKS-NRPs and wool thiopeptide SapB gene cluster.