Freshwaters play an essential role in providing ecosystem services worldwide, however, the water quality of different water bodies is strongly influenced by human activities such as urbanization, industry and agriculture. In this study, water and biofilm samples were collected from the main channel of the Danube River upstream and downstream of a metropolitan, from a regulated side arm within an urbanized area, and from two differently separated oxbow lakes located in nature conservation areas. The taxonomic diversity of bacterial communities was revealed by 16S rRNA gene-based amplicon sequencing using Illumina MiSeq platform. The results showed that all samples were dominated by phyla Pseudomonadota, Actinobacteriota and Bacteroidota. The bacterial community structures, however, clearly differentiated according to planktonic and epilithic or epiphytic habitats, as well as by riverine body types (main channel, side arm, oxbow lakes). The taxonomic diversity of biofilm communities was higher than that of planktonic ones in all studied habitats. Human impacts were mainly reflected in the slowly changing biofilm composition compared to the planktonic ones. Genera with pollution tolerance and/or degradation potential, such as Acinetobacter, Pseudomonas and Shewanella were mainly detected in biofilm communities of the highly urbanized section of the river side arm.

淡水在提供全球生态系统服务方面发挥着至关重要的作用，然而，不同水体的水质受到城市化、工业和农业等人类活动的强烈影响。在这项研究中，从大都市的多瑙河上游和下游主河道、城市化区域内的受监管侧臂以及位于自然保护区的两个不同分离的牛轭湖收集了水和生物膜样本。使用 Illumina MiSeq 平台，通过基于 16S rRNA 基因的扩增子测序揭示细菌群落的分类多样性。结果表明，所有样品均以假单胞菌门、放线杆菌门和拟杆菌门为主。然而，细菌群落结构根据浮游生物和附生或附生生境以及河流体型（主河道、侧臂、牛轭湖）明显区分。在所有研究的生境中，生物膜群落的分类多样性都高于浮游生物群落。与浮游生物膜相比，人类影响主要反映在缓慢变化的生物膜组成上。具有耐污染性和/或降解潜力的属，如不动杆菌属、假单胞菌属和希瓦氏菌属，主要在河滨臂高度城市化段的生物膜群落中检测到。