![]() ![]() The assembly of microorganisms in a local community is determined by the interaction of two types of ecological processes: deterministic (abiotic and biotic filtering) and stochastic (e.g., drift and dispersal) ( Chase and Myers, 2011 Stegen et al., 2012 Dini-Andreote et al., 2015). However, the taxonomy and functional potential of microbiomes associated with different horizons of permafrost soils are still relatively poorly understood. In addition, it has also been recognized that permafrost soil microbiomes have a high potential for nutrient metabolism ( Yergeau et al., 2010 Mackelprang et al., 2011 Woodcroft et al., 2018). Overall, these studies suggest that the variations in composition of permafrost soil microbiomes are related to the corresponding environmental conditions ( Gittel et al., 2014a Deng et al., 2015 Tripathi et al., 2018a). In recent years, there has been increasing interest in understanding the diversity and functional potential of microbiome residing in permafrost soils ( Yergeau et al., 2010 Mackelprang et al., 2011 Gittel et al., 2014a Deng et al., 2015 Woodcroft et al., 2018 Tripathi et al., 2018a). ![]() Permafrost soils harbor a diverse microbiome ( Jansson and Taş, 2014 Kwon et al., 2019), regardless of subfreezing temperatures and low nutrient availability. As soil microbiome plays a crucial role in decomposition and mineralization of organic matter in terrestrial ecosystems, it is important to have a better understanding of permafrost soil microbial ecology in order to improve our prediction of the potential consequences of climate warming on permafrost ecosystem function. Though the fate of the stored organic carbon in this region is still unclear, it is expected that the thawing of permafrost soils may trigger an increase in microbial activity promoting decomposition of formerly preserved organic matter and emission of greenhouse gases ( DeConto et al., 2012). However, this frozen carbon pool is being mobilized due to increased permafrost thaw and deepening of active layer thickness as a result of climate warming ( Jorgenson et al., 2001 Osterkamp, 2007 Romanovsky et al., 2010). Our study expands the knowledge on the structure and functional potential of microbiome associated with different horizons of permafrost soil, which could be useful in understanding the effects of environmental change on microbial responses in tundra ecosystems.Ībout a quarter of the Northern Hemisphere terrestrial ecosystems are covered by permafrost-underlain soils ( Zhang et al., 2008), which are key components in the global carbon cycle ( McGuire et al., 2009), and stored approximately 50% (~1,700 Pg) of the global below-ground soil organic carbon ( Tarnocai et al., 2009). The results of phylogenetic null modeling analysis showed that stochastic processes strongly influenced the composition of the microbiome in different soil horizons, except the bacterial community composition in top soil horizon, which was largely governed by homogeneous selection. The genes associated with carbon mineralization were more abundant in top soil horizon, while genes involved in acetogenesis, fermentation, methane metabolism (methanogenesis and methanotrophy), and N cycling were dominant in sub-soil horizons. The vertical gradient in soil physico-chemical parameters were strongly associated with composition of microbial communities across permafrost soil horizons however, a large fraction of the variation in microbial communities remained unexplained. The composition, diversity, and functions of microbiome varied significantly between soil horizons, with top soil horizon harboring more diverse communities than sub-soil horizons. Here we compared the taxonomic and functional composition of microbiome between different horizons of soil cores from a moist tussock tundra ecosystem in Council, Alaska, using 16S rRNA gene and shotgun metagenomic sequencing. However, knowledge about the taxonomy and functions of microbiome residing in different horizons of permafrost-underlain tundra soils is still limited. ![]() Permafrost-underlain tundra soils in Northern Hemisphere are one of the largest reservoirs of terrestrial carbon, which are highly sensitive to microbial decomposition due to climate warming. ![]() 2Environmental Safety Research Institute, NeoEnBiz, Bucheon, South Korea.1Korea Polar Research Institute, Incheon, South Korea.Tripathi 1 † Hye Min Kim 2 † Ji Young Jung 1 Sungjin Nam 1 Hyeon Tae Ju 1 Mincheol Kim 1 * Yoo Kyung Lee 1 * ![]()
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