RESUMEN
One hotspot of present community ecology is to uncover the mechanisms of community succession. In this study, two popular concepts, niche-neutrality dynamic balancing and co-occurrence network analysis, were integrated to investigate the dispersal dynamics of microbial communities in a freshwater river continuum in subtropical China. Results showed that when habitat conditions were mild and appropriate, such as in the clean upstream river, free of heavy pollution or long-lasting extreme disturbances, stochastic processes could increase species diversities, and organize communities into relatively loosely linked and stable networks with higher modularity and more modules. However, when conditions became degraded under heavy pollution, the influence of neutrality diminished, and niche-based selection imposed more constraints on communities and guided the assembling processes in certain directions: depleting species richness, strengthening interspecies connections and breaking boundaries of modules. Consequently, communities became more sensitive to fluctuations so as to deal with the harsh conditions efficiently. Another interesting finding was that, both as keystone taxa of communities, module hubs were mostly neutrally distributed generalists with high abundances, and were beneficial to many related operational taxonomic units. In contrast, connectors were less abundant and their distributions were more subjected to the environments. Therefore, connectors were probably responsible for the information transmission between microbial communities and environments, as well as between different modules, and thus could restrict the dispersal of microbes and guide the direction of community assembly.
Asunto(s)
Microbiota , China , Ecología , Agua Dulce , Microbiota/genética , RíosRESUMEN
Ammonia-oxidizing communities play important functional roles in the nitrification. However, environmental stresses can significantly affect this process by controlling the abundant communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) communities. In this study, we examined the abundance variations of ammonia-oxidizing communities using quantitative polymerase chain reaction (qPCR) and terminal-restriction fragment length polymorphism (T-RFLP) in a typical subtropical river, Luotian County, South Dabie Mountains, China. Clone libraries were conducted to evaluate the community structure and abundance of AOA and AOB in sediments. Results showed that Nitrososphaera sp and Nitrosopumilus sp were the most dominant AOA. The abundance of the AOA and AOB amoA gene ranged from 5.28 × 108 gene copies (g-soil-1) to 2.23 × 108 gene copies (g-soil-1) and 5.45 × 108 gene copies (g-soil-1) to 3.30 × 107 gene copies (g-soil-1), respectively. Five environmental variables, namely, ORP, DO, NO 3 - , Temp, and NH 4 + were played a major function in microbial communities of AOA and AOB in sediments. The T-RFLP profiles of AOA showed that 488 and 116 bp T-RFs were dominated. Overall, the results of this study showed that anthropogenic activities andenvironmental stress in rivers can alter the structure and function of microbes in their variable environment.
RESUMEN
This data-intensive study investigated the delicate balance of niche and neutrality underlying microbial communities in freshwater ecosystems through comprehensive application of high-throughput sequencing, species abundance distribution (SAD), and the neutral community model (NCM), combined with species diversity and phylogenetic measures, which unite the traditional and microbial ecology. On the genus level, 45.10% and 41.18% of the water samples could be explained by the log-normal and Volkov model respectively, among which 31.37% could fit both models. Meanwhile, 55.56% of the sediment samples could be depicted by the log-normal model, and Volkov-fitted samples comprised only 13.33%. Besides, operational taxonomic units (OTUs) from water samples fit Sloan's neutral model significantly better than those in sediment. Therefore, it was concluded that deterministic processes played a great role in both water and sediment ecosystems, whereas neutrality was much more involved in water assemblages than in non-fluidic sediment ecosystems. Secondly, log-normal fitted samples had lower phylogenetic species variability (PSV) than Volkov-fitted ones, indicating that niche-based communities were more phylogenetically clustered than neutrally assembled counterparts. Additionally, further testing showed that the relative richness of rare species was vital to SAD modeling, either niche-based or neutral, and communities containing fewer rare species were more easily captured by theoretical SAD models.