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TitleMicrobial functional diversity correlates with species diversity along a temperature gradient
AuthorRuhl, I A; Smirnova, A; Sharp, C E; Grasby, S EORCID logo; Strous, M; Dunfield, P F
SourcemBio vol. 7, issue 1, e00991-21, 2022 p. 1-16, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20210157
Mediapaper; on-line; digital
File formatpdf; html
SubjectsScience and Technology; temperature
Illustrationstables; charts; diagrams; cross-plots
ProgramGeoscience for New Energy Supply (GNES) Geothermal Energy
Released2022 01 01
AbstractMicrobial community diversity is often correlated with physical environmental stresses like acidity, salinity, and temperature. For example, species diversity usually declines with increasing temperature above 20°C. However, few studies have examined whether the genetic functional diversity of community metagenomes varies in a similar way as species diversity along stress gradients. Here, we investigated bacterial communities in thermal spring sediments ranging from 21 to 88°C, representing communities of 330 to 3,800 bacterial and archaeal species based on 16S rRNA gene amplicon analysis. Metagenomes were sequenced, and Pfam abundances were used as a proxy for metagenomic functional diversity. Significant decreases in both species diversity and Pfam diversity were observed with increasing temperatures. The relationship between Pfam diversity and species diversity followed a power function with the steepest slopes in the high-temperature, low-diversity region of the gradient. Species additions to simple thermophilic communities added many new Pfams, while species additions to complex mesophilic communities added relatively fewer new Pfams, indicating that species diversity does not approach saturation as rapidly as Pfam diversity does. Many Pfams appeared to have distinct temperature ceilings of 60 to 80°C. This study suggests that temperature stress limits both taxonomic and functional diversity of microbial communities, but in a quantitatively different manner. Lower functional diversity at higher temperatures is probably due to two factors, including (i) the absence of many enzymes not adapted to thermophilic conditions, and (ii) the fact that high-temperature communities are comprised of fewer species with smaller average genomes and, therefore, contain fewer rare functions.
Summary(Plain Language Summary, not published)
This study examines the controls of temperature on microbial functional diversity. Thermal spring sites in Canada were used to examine natural environments with temperatures varrying over 70 oC. Results show a clear control of temperature and that there is an optimal temperature range for life. These results may have relevance to impacts of future climate warming.

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