Accumulating evidence demonstrates that it is of great importance to maintain a stable and functional gut microbial community for host’s growth and health. However, gut microenvironment is constantly affected by diverse environmental factors. Salinity can cause stress, including hypersaline or hyposaline stress to aquatic species, thereby affecting their growth conditions. Razor clam (Sinonovacula constricta), an economically important bivalve species, inhabits in intertidal and estuarine zones and constantly experiences salinity stress. Yet little is known about how and to what extent clam gut microbiota is affected by salinity stress, while this knowledge is fundamental for clam aquaculture health management. To address this concern, this study compared the temporal differences of gut bacterial signatures and community assembly of S. constricta under normal salinity (NS), low salinity (LS), and high salinity (HS) conditions. Acute salinity stress affected the compositions, structures, and functional potentials of clam gut microbial community, of which salinity stress, hours post stress, and their interaction respectively constrained 7.6%, 16.4%, and 7.9% of community variation. Phylogenetic bin-based null model result revealed that the gut bacterial assembly of three salinity groups seemed to be largely driven by stochastic processes. Network analysis indicated that gut bacterial interspecies interaction exhibited less connected and lower cooperative activity under the conditions of LS and HS compared with NS. Notably, some pathogenic bacteria, including Vibrio and Pseudoalteromonas, were identified as keystone taxa of gut microbial networks in LS and HS groups. Above findings suggest that the clams under LS and HS conditions might be at a higher risk of developing disease. Our findings enhance the mechanism understanding of gut microbial assembly in S. constricta under abiotic factor challenge, which has important implications for clam health control from a microbial ecological perspective.

越来越多的证据表明，维持稳定和功能性的肠道微生物群落对于宿主的生长和健康非常重要。然而，肠道微环境不断受到多种环境因素的影响。盐度会对水生物种造成应激，包括高盐或低盐应激，从而影响其生长条件。缢蛏 ( Sinonovacula constricta ) 是一种重要的经济双壳类动物，栖息在潮间带和河口地区，经常遭受盐度胁迫。然而，人们对蛤肠道微生物群如何以及在多大程度上受到盐度胁迫的影响知之甚少，而这些知识对于蛤养殖健康管理至关重要。为了解决这个问题，本研究比较了正常盐度（NS）、低盐度（LS）和高盐度（HS）条件下肠道细菌特征和缢蛏群落组装的时间差异。急性盐度胁迫影响蛤肠道微生物群落的组成、结构和功能潜力，其中盐度胁迫、胁迫后小时及其相互作用分别限制了群落变异的7.6%、16.4%和7.9%。基于系统发育箱的零模型结果表明，三个盐度组的肠道细菌组装似乎很大程度上是由随机过程驱动的。网络分析表明，与 NS 相比，LS 和 HS 条件下肠道细菌种间相互作用表现出较少的连接和较低的合作活性。值得注意的是，一些病原菌，包括弧菌和假交替单胞菌，被确定为 LS 和 HS 组肠道微生物网络的关键类群。上述研究结果表明，在 LS 和 HS 条件下的蛤患疾病的风险可能更高。我们的研究结果增强了对非生物因素挑战下缢蛏肠道微生物组装机制的理解，这从微生物生态角度对蛤的健康控制具有重要意义。