Observational study reveals distinct denitrifying bacterial community structures across littoral biotopes in Lake Baikal, highlighting niche-specific drivers of nitrogen cycling.
Key Points
To characterize the diversity, taxonomic composition, and environmental determinants of denitrifying bacterial communities across diverse littoral biotopes in Southern Lake Baikal.
Sampled four littoral biotopes in Southern Lake Baikal: epilithic biofilms on rocky substrates, the surface microlayer, the water column, and the near-bottom water layer.
Conducted high-throughput amplicon sequencing targeting the nitrite reductase functional genes nirK and nirS.
Modeled environmental drivers of community structure across biotopes using distance-based redundancy analysis (db-RDA).
nirS-type denitrifiers were dominated by Betaproteobacteria (64.9%), Alphaproteobacteria (28.6%), and Gammaproteobacteria (6.5%), with Rhodocyclaceae (25%) leading epilithic biofilms and Azonexaceae (23.6–36.6%) prevailing in water layers.
nirK-type denitrifiers comprised Alphaproteobacteria (99.96%) and Gemmatimonadia (0.04%), with Paracoccaceae (66.3–84.4%) and the genus Tabrizicola (59.4–76.7%) dominating all biotopes.
Distance-based redundancy analysis identified nitrate nitrogen as a significant determinant of nirK community structure, whereas nirS communities showed no significant correlations with tested environmental factors.