Zhang Guohua, Liu Shufeng, Du Wenran, Li Yinghao, Wu Zongzhi, Liu Tang, Wang Yichu
Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing, China.
College of Resources and Environmental Sciences, China Agricultural University, Beijing, China.
Front Microbiol. 2024 Dec 11;15:1444206. doi: 10.3389/fmicb.2024.1444206. eCollection 2024.
Sediments are key reservoirs for rare bacterial biospheres that provide broad ecological services and resilience in riverine ecosystems. Compared with planktons, there is a lack of knowledge regarding the ecological differences between abundant and rare taxa in benthic bacteria along a large river. Here, we offer comprehensive insights into the spatiotemporal distributions, co-occurrence networks, and assembly processes of three divided categories namely always rare taxa (ART), conditionally rare taxa (CRT), and conditionally rare and abundant taxa (CRAT) in sediments covering a distance of 4,300 km in the Yangtze River. Our study demonstrated that ART/CRT contributed greatly to the higher Chao-1 index, Shannon-Wiener index, and phylogenetic alpha diversity of benthic bacteria in autumn than in spring. ART showed high overall beta diversity, and CRT/CRAT exhibited more significant distance-decay patterns than ART in both seasons, mainly corresponding to macroscopic landform types. CRT predominated the nonrandom co-occurrence network, with 97% of the keystone species mostly affiliated with Acidobacteriota flourishing in the lower-reach plain. Two selection processes had the greatest influences on the assembly of CRT (74.7-77.6%), whereas CRAT were driven primarily by dispersal limitation (74.9-86.8%) and ART were driven by heterogeneous selection (33.9-48.5%) and undominated stochasticity (32.7-36.5%). Natural factors such as river flow and channel slope exhibited more significant correlations with community variation than nutrients in all three groups, and total organic carbon mediated the balance among the distinct assembly processes of the ART and CRT in both seasons. Taken together, these results provide an improved ecological understanding of the discrepancy in biogeographic patterns between abundant and rare bacterial taxa in the sediments of Asia's largest river.
沉积物是稀有细菌生物圈的关键储存库，为河流生态系统提供广泛的生态服务和恢复力。与浮游生物相比，我们对大型河流底栖细菌中丰富类群和稀有类群之间的生态差异缺乏了解。在此，我们全面深入地研究了长江4300公里范围内沉积物中三类不同的分类群，即始终稀有类群（ART）、条件稀有类群（CRT）和条件稀有且丰富类群（CRAT）的时空分布、共现网络和组装过程。我们的研究表明，秋季底栖细菌的Chao-1指数、香农-维纳指数和系统发育α多样性高于春季，ART/CRT对此贡献巨大。ART总体上表现出较高的β多样性，在两个季节中，CRT/CRAT比ART表现出更显著的距离衰减模式，这主要与宏观地形类型相对应。CRT在非随机共现网络中占主导地位，97%的关键物种大多隶属于在下游平原繁盛的酸杆菌门。两种选择过程对CRT的组装影响最大（74.7-77.6%），而CRAT主要受扩散限制驱动（74.9-86.8%），ART受异质选择（33.9-48.5%）和非主导随机性（32.7-36.5%）驱动。在所有三个类群中，诸如河流流量和河道坡度等自然因素与群落变化的相关性比养分更为显著，总有机碳在两个季节中介导了ART和CRT不同组装过程之间的平衡。综上所述，这些结果为更好地从生态学角度理解亚洲最大河流沉积物中丰富和稀有细菌类群生物地理模式的差异提供了依据。
