Temperature alters bacterial community structure in sediment of mountain stream.

Temperature and nutrients are known as crucial drivers for the variations of bacterial community structure and functions in oceans and lakes. However, their significance and mechanisms in influencing the bacterial community structure and function in mountain stream remain unclear. In this study, we investigated the spatiotemporal patterns of the bacterial communities and the main environmental factors in the Taizicheng River, a high-latitude mountainous stream, to reveal the main driving factors for sedimental bacterial communities. Our findings identified that the phyla Acidobacteriota and Bacteroidota served as the strong discriminant for sedimental bacterial community in the non-freezing and freezing periods, respectively. In contrast, no significant difference was detected in bacterial functional composition. Mantel test and Redundancy analysis showed that temperature and nutrients played significant roles in determining the bacterial community structure and temperature critically influenced the bacterial metabolic processes. The results of partial least squares path model demonstrated that temperature affected the bacterial community structure in both directly (43.70%) and indirectly pathways (41.10%) by affecting the sediment parameters. However, the functional composition was not significantly affected by temperature and nutrients. Our results highlight that the change of temperature can significantly alters the structure of bacterial communities rather than functional composition and provides new insights into the response mechanisms of bacterial communities to environmental factors which contributes to the deep understanding of the driving factors as well as the protection strategies for microbial communities in mountain stream and aquatic ecosystem.