Differential Functional Constraints Cause Strain-Level Endemism in Polynucleobacter Populations
- Argonne National Lab. (ANL), Argonne, IL (United States). Biosciences Division; Univ. of Chicago, Chicago, Illinois (United States). Dept. of Surgery and Dept. of Ecology and Evolution
- Argonne National Lab. (ANL), Argonne, IL (United States). Biosciences Division
- Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division
- Metropolitan Water Reclamation District of Greater Chicago, Cicero, IL (United States)
The adaptation of bacterial lineages to local environmental conditions creates the potential for broader genotypic diversity within a species, which can enable a species to dominate across ecological gradients because of niche flexibility. The genus Polynucleobacter maintains both free-living and symbiotic ecotypes and maintains an apparently ubiquitous distribution in freshwater ecosystems. Subspecies-level resolution supplemented with metagenome-derived genotype analysis revealed that differential functional constraints, not geographic distance, produce and maintain strain-level genetic conservation in Polynucleobacter populations across three geographically proximal riverine environments. Genes associated with cofactor biosynthesis and one-carbon metabolism showed habitat specificity, and protein-coding genes of unknown function and membrane transport proteins were under positive selection across each habitat. Characterized by different median ratios of nonsynonymous to synonymous evolutionary changes (dN/dS ratios) and a limited but statistically significant negative correlation between the dN/dS ratio and codon usage bias between habitats, the free-living and core genotypes were observed to be evolving under strong purifying selection pressure. Highlighting the potential role of genetic adaptation to the local environment, the two-component system protein-coding genes were highly stable (dN/dS ratio, < 0.03). These results suggest that despite the impact of the habitat on genetic diversity, and hence niche partition, strong environmental selection pressure maintains a conserved core genome for Polynucleobacter populations.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER). Biological Systems Science Division
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1626163
- Journal Information:
- mSystems, Vol. 1, Issue 3; ISSN 2379-5077
- Publisher:
- American Society for MicrobiologyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Gene Expansion and Positive Selection as Bacterial Adaptations to Oligotrophic Conditions
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journal | February 2019 |
Microdiversity ensures the maintenance of functional microbial communities under changing environmental conditions
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journal | August 2019 |
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