State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou 570228, Chinese mainland.
Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai 519082, Chinese mainland.
FEMS Microbiol Ecol. 2024 Nov 23;100(12). doi: 10.1093/femsec/fiae146.
Along the river-sea continuum, microorganisms are directionally dispersed by water flow while being exposed to strong environmental gradients. To compare the two assembly mechanisms that may strongly and differently influence metacommunity dynamics, namely homogenizing dispersal and heterogeneous selection, we characterized the total (16S rRNA gene) and putatively active (16S rRNA transcript) bacterial communities in the Pearl River-South China Sea Continuum, during the wet (summer) and dry (winter) seasons using high-throughput sequencing. Moreover, well-defined sampling was conducted by including freshwater, oligohaline, mesohaline, polyhaline, and marine habitats. We found that heterogeneous selection exceeded homogenizing dispersal in both the total and active fractions of bacterial communities in two seasons. However, homogeneous selection was prevalent (the dominant except in active bacterial communities during summer), which was primarily due to the bacterial communities' tremendous diversity (associated with high rarity) and our specific sampling design. In either summer or winter seasons, homogeneous and heterogeneous selection showed higher relative importance in total and active communities, respectively, implying that the active bacteria were more responsive to environmental gradients than were the total bacteria. In summary, our findings provide insight into the assembly of bacterial communities in natural ecosystems with high spatial connectivity and environmental heterogeneity.
在陆海连续体上，微生物在水流的作用下沿水流方向被定向扩散，同时受到强烈的环境梯度的影响。为了比较可能强烈且不同地影响集居群落动态的两种组装机制，即均匀扩散和异质选择，我们利用高通量测序技术，在雨季（夏季）和旱季（冬季），对珠江-南海连续体中的总（16S rRNA 基因）和假定活性（16S rRNA 转录物）细菌群落进行了特征描述，采样范围包括淡水、寡盐、中盐、多盐和海洋生境。我们发现，在两个季节的总群落和活性群落中，异质选择均超过了均匀扩散。然而，在夏季的活性细菌群落中，均匀选择占主导地位（除了活性细菌群落之外），这主要是由于细菌群落的巨大多样性（与高稀有性相关）和我们特定的采样设计。无论是在夏季还是冬季，均匀选择和异质选择在总群落和活性群落中的相对重要性都更高，这意味着活性细菌比总细菌对环境梯度的反应更敏感。总之，我们的研究结果为具有高空间连通性和环境异质性的自然生态系统中的细菌群落组装提供了新的见解。
