The influence of changing salinity on community composition and functional activity (Bacterial Production (BP) and ectoenzyme activity) of major bacterial taxa was evaluated using microcosm experiments in a tropical monsoon influenced estuary. Natural bacterial inocula at different salinities, representing marine, brackish, and freshwater, were inter-transferred and elucidated their response with an emphasis on community composition and β-Glucosidase (BGase) activity. The results revealed a significant decrease in the total bacterial count (TBC) and BP on the translocation of bacterial inocula to different salinity conditions in the case of freshwater bacteria. However, a significant increase in BGase activity coupled with shifts in the studied bacterial groups was evident in the case of marine as well as freshwater bacteria. Quantitative PCR (qPCR) revealed a shift in major bacterial taxa upon translocation to different waters, which was dependent on salinity and the source of inocula. Redundancy and qPCR analyses showed that members belonging to Gammaproteobacteria and Betaproteobacteria were higher, and possibly influenced BGase activity in marine and freshwater, respectively. Translocation of marine inocula to brackish and freshwater resulted in an emergence of Bacteroidetes, Actinobacteria, and Betaproteobacteria, respectively. Whereas, when freshwater inocula were translocated to marine or brackish water, Alphaproteobacteria and Gammaproteobacteria taxa emerged, and this was coupled with increased BGase activity. In contrast, brackish water bacteria showed a strong persistence in bacterial community composition when translocated to different salinities within this estuary. Such phylogenetic persistence or changes suggests species level shifts in specific bacterial taxa, and unravelling the same using different functional gene markers would ascertain their role in organic matter processing and is way forward.

在热带季风影响的河口使用缩影实验评估了盐度变化对主要细菌类群的群落组成和功能活性（细菌产生（BP）和外部酶活性）的影响。分别转移了代表海洋，咸淡水和淡水的不同盐度的天然细菌接种物，并阐明了它们的反应，重点是群落组成和β-葡萄糖苷酶（BGase）活性。结果表明，在淡水细菌的情况下，总细菌数（TBC）和血压显着降低了细菌接种物向不同盐度条件下的转运。然而，在海洋细菌和淡水细菌的情况下，BGase活性的显着增加以及所研究细菌群的转移是显而易见的。定量PCR（qPCR）显示，主要细菌类群在转移到不同水域时发生了转移，这取决于盐度和接种源。冗余和qPCR分析表明，属于γ-变形杆菌和β-变形杆菌的成员较高，并且可能分别影响了海洋和淡水中的BGase活性。海洋接种物向咸淡水和淡水的易位分别导致了拟杆菌，放线菌和β变形杆菌的出现。然而，当淡水接种物转移到海水或微咸水中时，出现了变形杆菌和γ变形杆菌类群，这与增加的BGase活性有关。相反，当在该河口内转移至不同盐度时，微咸水细菌在细菌群落组成中表现出强烈的持久性。这种系统发育的持久性或变化表明特定细菌类群中的物种水平发生了变化，使用不同的功能基因标记物对其进行分类将确定它们在有机物质加工中的作用，并且是前进的道路。