Global distribution of cyanobacterial ecotypes in the cold biosphere

Abstract

Perennially cold habitats are diminishing as a result of climate change; however, little is known of the diversity or biogeography of microbes that thrive in such environments. Here we use targeted 16S rRNA gene surveys to evaluate the global affinities of cold-dwelling cyanobacteria from lake, stream and ice communities living at the northern limit of High Arctic Canada. Pigment signature analysis by HPLC confirmed the dominance of cyanobacteria in the phototrophic communities of these High Arctic microbial mats, with associated populations of chlorophytes and chromophytes. Microscopic analysis of the cyanobacteria revealed a diverse assemblage of morphospecies grouping into orders Oscillatoriales, Nostocales and Chroococcales. The 16S rRNA gene sequences from six clone libraries grouped into a total of 24 ribotypes, with a diversity in each mat ranging from five ribotypes in ice-based communities to 14 in land-based pond communities. However, no significant differences in composition were observed between these two microbial mat systems. Based on clone-library and phylogenetic analysis, several of the High Arctic ribotypes were found to be 499% similar to Antarctic and alpine sequences, including to taxa previously considered endemic to Antarctica. Among the latter, one High Arctic sequence was found 99.8% similar to Leptolyngbya antarctica sequenced from the Larsemann Hills, Antarctica. More than 68% of all identified ribotypes at each site matched only cyanobacterial sequences from perennially cold terrestrial ecosystems, and were o97.5% similar to sequences from warmer environments. These results imply the global distribution of low-temperature cyanobacterial ecotypes throughout the cold terrestrial biosphere.

Pole-to-Pole Connections: Similarities between Arctic and Antarctic Microbiomes and Their Vulnerability to Environmental Change

“…We conclude that the microbiota of both polar regions may be more connected than previously assumed and our data suggest a biogeographical connection between both poles, consistent with some previous studies Jungblut et al, 2010;Chrismas et al, 2015;Cox et al, 2016;Biersma et al, 2017;Mohit et al, 2017). The polar microbial communities in our study are an assemblage of ubiquitously-distributed and potentially endemic taxa.…”

“…DNA extracts were stored frozen (−20 • C) for no longer than three months before subsequent processing. Samples from Northern Canada were extracted as described in Jungblut et al (2010), dried and stored frozen.…”

“…The polar regions therefore provide a unique opportunity to test biogeographic patterns of microbial diversity, providing predictors/indications of the future consequences of environmental change. The survival strategies and dispersal limitations, genetic identity and endemic character of polar microorganisms and, thus, their resilience and sensitivity are still under discussion (Vincent, 2000b;Taton et al, 2006;Jungblut et al, 2010;Vyverman et al, 2010). A comprehensive exploration of these microbial features using consistent methodology and sampling has been difficult to date due to the remoteness and inaccessibility of the polar regions.…”

Species concepts and speciation factors in cyanobacteria, with connection to the problems of diversity and classification

“…On the other hand, 16S-23S ITS phylogenies of the freshwater, planktic cyanobacterium Microcystis aeruginosa revealed no connection between geographic position and a placement in phylogeny (van Gremberghe et al 2011). Further, no geographical patterning has been observed in polar cyanobacteria based on 16S rRNA (Jungblut et al 2010). Taken together, the role of geographical isolation as it relates to the speciation of microbes should be further investigated using whole genome data or using more variable genome regions (Ramette and Tiedje 2007).…”

Late Holocene changes in cyanobacterial community structure in maritime Antarctic lakes

“…Recent studies have shown that polar and alpine regions harbor a flora that is in part composed of typical cold-adapted microbes (Jungblut et al 2009;Souffreau et al 2013), including taxa that are (potentially) endemic to Antarctica (Sabbe et al 2003;Taton et al 2006a). Many of these regions have recently entered a period of rapid warming, which has already had an impact on the physical and chemical structure, biodiversity and functioning of their aquatic ecosystems (Quayle et al 2002;Smol et al 2005;Smol and Douglas 2007).…”