Adhikari Namita Paudel, Adhikari Subash, Rijal Komal Raj
Center for the Pan-Third Pole Environment, Lanzhou University, Lanzhou, 730000, China.
State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China.
Int Microbiol. 2024 Oct 14. doi: 10.1007/s10123-024-00607-6.
Bacteria have two trophic lifestyles in aquatic ecosystems, i.e., free-living (FL) and particle-attached (PA), with different but essential ecological roles. However, relevant knowledge is still dearth in the upstream source region of the Himalayan Rivers. Thus, we emphasized a comparative study on community composition, co-occurrence, and geographic distribution of the FL and PA bacteria and the effect of environmental factors in the source region of the Ganges and Brahmaputra Rivers. PA bacteria relative to FL harbored a significantly higher local diversity, richness, and evenness. A significantly higher abundance of Betaproteobacteria, Verrucomicrobiota, and Planctomycetota in PA trophic lifestyle and Gammaproteobacteria and Actinomycetota in FL tropic lifestyle and indicator OTUs belonging to related taxa were observed. The spatial variation of the FL and PA bacterial communities was most significantly impacted by dispersal limitation as a discrete factor. Among the environmental parameters, the total nitrogen (TN) was found to be a significant (P < 0.001) driver of the variation in PA communities. Meanwhile, particulate organic carbon (POC) and TN considerably explained the variation of FL communities. A significant correlation (P < 0.001) of TN with dominant bacterial taxa (Pseudomonadota, Actinomycetota, and Verrucomicrobiota) and FL and PA indicator OTUs associated with these taxa further confirmed nitrogen as the limiting nutrient in the source region of the Ganges and Brahmaputra Rivers. The co-occurrence network topological characteristics showed that the PA network was more stable than the FL network, which was more complicated and unstable. Thus, it can be speculated that FL communities relative to PA are more vulnerable to shifting upon disturbances.
细菌在水生生态系统中有两种营养生活方式，即自由生活（FL）和附着颗粒（PA），它们具有不同但至关重要的生态作用。然而，在喜马拉雅河流的上游源头地区，相关知识仍然匮乏。因此，我们着重对恒河和雅鲁藏布江源头地区FL和PA细菌的群落组成、共现情况和地理分布以及环境因素的影响进行了比较研究。相对于FL，PA细菌具有显著更高的局部多样性、丰富度和均匀度。观察到在PA营养生活方式中β-变形菌纲、疣微菌门和浮霉菌门的丰度显著更高，在FL营养生活方式中γ-变形菌纲和放线菌门的丰度显著更高，并且发现了属于相关分类群的指示性操作分类单元。作为一个离散因素，扩散限制对FL和PA细菌群落的空间变异影响最为显著。在环境参数中，总氮（TN）被发现是PA群落变异的一个显著（P < 0.001）驱动因素。同时，颗粒有机碳（POC）和TN相当程度地解释了FL群落的变异。TN与优势细菌分类群（假单胞菌门、放线菌门和疣微菌门）以及与这些分类群相关的FL和PA指示性操作分类单元之间存在显著相关性（P < 0.001），这进一步证实了氮是恒河和雅鲁藏布江源头地区的限制营养元素。共现网络拓扑特征表明，PA网络比FL网络更稳定，FL网络更复杂且不稳定。因此，可以推测相对于PA，FL群落更容易受到干扰而发生变化。
