Regional Centre, CSIR-National Institute of Oceanography, Dr. Salim Ali Road, Post Box No. 1913, Kochi, Kerala, 682 018, India.
Space Application Centre, Jodhpur Tekra, Ahmadabad, Gujarat, 380015, India.
Mol Biol Rep. 2019 Jun;46(3):3113-3127. doi: 10.1007/s11033-019-04766-y. Epub 2019 Apr 1.
Upwelling and mud banks are two prominent oceanographic features in the coastal waters along the south west coast of India during the southwest monsoon (MON) season. The present study investigates the microbial diversity in the coastal environments of Alappuzha, India, where upwelling and mud banks co-exist. Water samples were collected from three stations, M1, M2, and M3, on a weekly basis to estimate the physico-chemical parameters and microbial abundance (MA). Presence of cold waters (< 26 °C) with high nitrate (6-8 µM) and low dissolved oxygen (5 µM) in the sub surface waters during monsoon (M) confirmed the presence of upwelling at all the three stations. Simultaneously, presence of unusually calm waters was seen at M2 alone during M indicating the formation of mud banks. The microbial diversity was determined from three stations, with distinct oceanographic conditions (M1: coastal reference station with only upwelling, M2: mud banks + upwelling, and M3: offshore reference station with only upwelling). The water samples were collected during two seasons, pre-monsoon (April) and M (July) and analysed using 16S rRNA-based Illumina high-throughput metagenomic sequencing. Proteobacteria was the most dominant phyla, followed by Bacteroidetes, Firmicutes, Cyanobacteria, Actinobacteria, and Verrucomicrobia in order, with variations in their relative abundance spatially and seasonally. Though the MA increased during M at all the stations, the relative abundance of most of the bacterial phyla except Proteobacteria decreased during M season. Interestingly, most of the sequences at M2 during mud banks were unclassified at the class level indicating the presence of unique microbial populations in this station. Prediction of metabolic activity revealed ammonia oxidation, nitrite reduction, sulphate reduction, xylan degradation, dehalogenation, chitin degradation, etc. as important functions. The metabolic activity throws light on the role of microbes in this environment thereby providing a system-scale perspective of microbial community interactions.
上升流和泥滩是印度西南海岸沿海水域在西南季风（MON）季节的两个突出海洋特征。本研究调查了印度阿勒皮沿海环境中的微生物多样性，那里存在上升流和泥滩共存的情况。每周从三个站点 M1、M2 和 M3 收集水样，以估计水的理化参数和微生物丰度（MA）。在季风期间，次表层水中存在冷水（<26°C），高硝酸盐（6-8µM）和低溶解氧（5µM），这证实了所有三个站点都存在上升流。同时，仅在 M 期间，M2 站点出现了异常平静的水域，表明泥滩的形成。从三个具有明显海洋条件的站点确定了微生物多样性（M1：仅上升流的沿海参考站，M2：泥滩+上升流，M3：仅上升流的近海参考站）。水样分别在季风前（四月）和季风期间（七月）采集，并使用基于 16S rRNA 的 Illumina 高通量宏基因组测序进行分析。结果表明，变形菌门是最主要的门，其次是拟杆菌门、厚壁菌门、蓝藻门、放线菌门和疣微菌门，它们在空间和季节上的相对丰度存在差异。尽管在所有站点，MA 在季风期间增加，但除变形菌门外，大多数细菌门的相对丰度在季风期间下降。有趣的是，在 M2 站点泥滩期间，大多数序列在分类级别上未被分类，这表明该站点存在独特的微生物种群。代谢活性预测表明氨氧化、亚硝酸盐还原、硫酸盐还原、木聚糖降解、脱卤、几丁质降解等是重要的功能。代谢活性揭示了微生物在该环境中的作用，从而提供了微生物群落相互作用的系统范围的视角。
