Recent applications of molecular genetics to edaphic microbial communities of the McMurdo Dry Valleys and elsewhere have rejected a long-held belief that Antarctic soils contain extremely limited microbial diversity. The Inter-Valley Soil Comparative Survey aims to elucidate the factors shaping these unique microbial communities and their biogeography by integrating molecular genetic approaches with biogeochemical analyses. Although the microbial communities of Dry Valley soils may be complex, there is little doubt that the ecosystem's food web is relatively simple, and evidence suggests that physicochemical conditions may have the dominant role in shaping microbial communities. To examine this hypothesis, bacterial communities from representative soil samples collected in four geographically disparate Dry Valleys were analyzed using molecular genetic tools, including pyrosequencing of 16S rRNA gene PCR amplicons. Results show that the four communities are structurally and phylogenetically distinct, and possess significantly different levels of diversity. Strikingly, only 2 of 214 phylotypes were found in all four valleys, challenging a widespread assumption that the microbiota of the Dry Valleys is composed of a few cosmopolitan species. Analysis of soil geochemical properties indicated that salt content, alongside altitude and Cu2+, was significantly correlated with differences in microbial communities. Our results indicate that the microbial ecology of Dry Valley soils is highly localized and that physicochemical factors potentially have major roles in shaping the microbiology of ice-free areas of Antarctica. These findings hint at links between Dry Valley glacial geomorphology and microbial ecology, and raise previously unrecognized issues related to environmental management of this unique ecosystem.
In Arctic wet tundra, microbial controls on organic matter decomposition are likely to be altered as a result of climatic disruption. Here, we present a study on the activity, diversity and vertical distribution of methane-cycling microbial communities in the active layer of wet polygonal tundra on Herschel Island. We recorded potential methane production rates from 5 to 40 nmol h À1 g À1wet soil at 10°C and significantly higher methane oxidation rates reaching values of 6-10 lmol h À1 g À1 wet soil. Terminal restriction fragment length polymorphism (T-RFLP) and cloning analyses of mcrA and pmoA genes demonstrated that both communities were stratified along the active layer vertical profile. Similar to other wet Arctic tundra, the methanogenic community hosted hydrogenotrophic (Methanobacterium) as well as acetoclastic (Methanosarcina and Methanosaeta) members. A pronounced shift toward a dominance of acetoclastic methanogens was observed in deeper soil layers. In contrast to related circum-Arctic studies, the methane-oxidizing (methanotrophic) community on Herschel Island was dominated by members of the type II group (Methylocystis, Methylosinus, and a cluster related to Methylocapsa). The present study represents the first on methane-cycling communities in the Canadian Western Arctic, thus advancing our understanding of these communities in a changing Arctic.
A novel, moderately halophilic, endospore-forming bacterial strain, designated Hal 1 T , was isolated from a permafrost core collected from the Canadian high Arctic. The temperature for growth of strain Hal 1 T was 0-30 6C with no growth observed at either "5 or 37 6C (optimum growth at about 25 6C). Strain Hal 1 T was able to grow at NaCl concentrations of 0-20 % (w/v) and did not have an absolute NaCl requirement for growth; optimal growth was at 5 % (w/v) NaCl. At the time of writing, the genus Virgibacillus comprised 14 recognized species Chen et al., 2008;Heyndrickx et al., 1999;Heyrman et al., 2003; Hua et al., 2008;Lee et al., 2006a; Quesada et al., 2007;Yoon et al., 2004bYoon et al., , 2005Wang et al., 2008). et al., 2007) was added to 50 ml of J HM medium and incubated with shaking at 37, 23 and 5 u C. Growth was noted after 2 weeks incubation at 23 uC and after 1 month at 5 uC. An aliquot of the enrichments was plated on J HM plates, and single colonies were selected. Strain Hal 1 T was the dominant colony type from both the 23 and the 5 u C enrichments as verified by sequencing a partial region of the 16S rRNA gene [100 % sequence similarity identity by using primers 27F and 758R; see Steven et al. (2007) for PCR conditions and primer sequences]. DNA was isolated from a single colony of strain Hal 1 T and the almost-complete 16S rRNA gene was PCR amplified and sequenced as outlined by Steven et al. (2008). In brief, DNA was isolated by using the Gram-positive protocol of the DNeasy Tissue kit (Qiagen) and the 16S rRNA gene was PCR amplified and sequenced by using primers 27F and 1492R (Lane, 1991).The 16S rRNA gene sequence of strain Hal 1 T showed highest similarity (98.2 % over 1350 bp) to both Abbreviation: RAPD, randomly amplified polymorphic DNA.The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain Hal 1 T is EF675742.RAPD results from comparisons of strain Hal 1 T and the type strains of recognized Virgibacillus species are available as supplementary material with the online version of this paper.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.