Department of Animal Science, University of Ljubljana, Domzale, Slovenia.
PLoS One. 2013 Sep 26;8(9):e76440. doi: 10.1371/journal.pone.0076440. eCollection 2013.
The Himalaya with its altitude and geographical position forms a barrier to atmospheric transport, which produces much aqueous-particle monsoon precipitation and makes it the largest continuous ice-covered area outside polar regions. There is a paucity of data on high-altitude microbial communities, their native environments and responses to environmental-spatial variables relative to seasonal and deglaciation events.
METHODOLOGY/PRINCIPAL FINDINGS: Soils were sampled along altitude transects from 5000 m to 6000 m to determine environmental, spatial and seasonal factors structuring bacterial communities characterized by 16 S rRNA gene deep sequencing. Dust traps and fresh-snow samples were used to assess dust abundance and viability, community structure and abundance of dust associated microbial communities. Significantly different habitats among the altitude-transect samples corresponded to both phylogenetically distant and closely-related communities at distances as short as 50 m showing high community spatial divergence. High within-group variability that was related to an order of magnitude higher dust deposition obscured seasonal and temporal rearrangements in microbial communities. Although dust particle and associated cell deposition rates were highly correlated, seasonal dust communities of bacteria were distinct and differed significantly from recipient soil communities. Analysis of closest relatives to dust OTUs, HYSPLIT back-calculation of airmass trajectories and small dust particle size (4-12 µm) suggested that the deposited dust and microbes came from distant continental, lacustrine and marine sources, e.g. Sahara, India, Caspian Sea and Tibetan plateau. Cyanobacteria represented less than 0.5% of microbial communities suggesting that the microbial communities benefitted from (co)deposited carbon which was reflected in the psychrotolerant nature of dust-particle associated bacteria.
CONCLUSIONS/SIGNIFICANCE: The spatial, environmental and temporal complexity of the high-altitude soils of the Himalaya generates ongoing disturbance and colonization events that subject heterogeneous microniches to stochastic colonization by far away dust associated microbes and result in the observed spatially divergent bacterial communities.
喜马拉雅山的海拔和地理位置形成了大气传输的屏障，产生了大量的含水粒子季风降水，使其成为极地以外最大的连续冰雪覆盖区。与季节性和冰川消退事件相比，关于高海拔微生物群落、其原生环境以及对环境空间变量的响应的数据很少。
方法/主要发现：从 5000 米到 6000 米的海拔梯度上采集土壤样本，以确定通过 16S rRNA 基因深度测序来描述的细菌群落的环境、空间和季节性因素。使用灰尘陷阱和新鲜雪样本来评估灰尘丰度和活力、灰尘相关微生物群落的群落结构和丰度。海拔梯度样本之间的显著不同生境对应于短至 50 米的系统发育上遥远和密切相关的群落，表现出高群落空间离散度。与灰尘沉积率高度相关的高组内变异性掩盖了微生物群落的季节性和时间性排列。尽管灰尘颗粒和相关细胞沉积率高度相关，但细菌的季节性灰尘群落是独特的，与接收土壤群落有显著差异。对灰尘 OTUs 的近亲分析、空气团轨迹的 HYSPLIT 反向计算以及灰尘颗粒较小（4-12 µm）表明，沉积的灰尘和微生物来自遥远的大陆、湖泊和海洋源，例如撒哈拉沙漠、印度、里海和青藏高原。蓝细菌占微生物群落的比例不到 0.5%，这表明微生物群落受益于（共）沉积的碳，这反映在灰尘颗粒相关细菌的耐寒特性上。
结论/意义：喜马拉雅山高海拔土壤的空间、环境和时间复杂性产生了持续的干扰和殖民化事件，使异质小生境受到来自遥远灰尘相关微生物的随机殖民化，导致观察到的空间离散细菌群落。
