Characterization Free-living (FL) and Particle-attached (PA) bacterial communities of a canyon river reservoir on Yungui Plateau, China

Abstract Bacteria play an important role in nutrient recycling and energy conversion in any aquatic ecosystem. Revealing the composition of free-living (FL) and particle-attached (PA) bacterial communities provide insights into their roles for biogeochemical processes and algal bloom dynamics. This study revealed the structure of FL and PA bacterial communities in a canyon reservoir in the Yungui-Plateau region, southern China. Firstly, we compared the difference using 3.0 µm and 5.0 µm filter for PA and FL bacterial communities (defined as PA3, FL3 and PA5, FL5), in order to choose the better sampling protocol. Secondly, we identified the differences between FL and PA in respect of their composition, diversity as well as function. Results showed that (1) dominant taxa did not change between FL3 and FL5, PA3 and PA5, but the relative abundance varied. Community composition and predicted gene functions showed significant differences between PA3 and PA5, while insignificant difference was noticed between FL3 and FL5; (2) FL was dominated by Actinobacteria and Proteobacteria, while PA was dominated by Planctomycetes and Proteobacteria; (3) there was insignificant difference on α-diversity between PA3 and PA3, but PA5 community exhibited greater dissimilarity (β-diversity) than PA3; (4) differences were detected between FL and PA community, with PA community exhibiting greater diversity and metabolic versatility than FL; (5) nitrogen metabolism related genes were abundant, implying an important role of both FL and PA in aquatic nitrogen cycling and hence in the microbial loop in this reservoir. This study provided evidence for using 5.0 µm filter to separate PA bacterial community, and also presented fundamental information on FL and PA bacterioplankton in Wujiangdu reservoir.