Abstract Oxygen minimum zones (OMZs) are unique, widely spread and well-studied features of the global ocean, varying in seasonality and intensity. The Northern Indian Ocean contains OMZs in the Arabian Sea (AS-OMZ) and the Bay of Bengal (BB-OMZ) having unique biogeochemical features. OMZ water column harbours distinct microbial communities that play vital roles in ocean biogeochemical cycles. Sulphur cycling processes facilitated by OMZ microbial communities are poorly understood with regards to different microbial groups involved, spatially and temporally. Here we sampled different stations in the AS-OMZ and BB-OMZ across dissolved oxygen gradients, to obtain culturable sulphur-oxidising bacterial (SOB) diversity using modified agar-based media. Phylogenetic analysis of the isolates placed the majority of them in Phylum Proteobacteria, followed by Actinobacteria, Firmicutes, and Bacteroidetes. Analyses of thiosulphate oxidation potential of isolates revealed that an α-proteobacteria, Citreicella thiooxidans and a β-proteobacterial species, Achromobacter xylosoxydans oxidised thiosulphate to sulphate within 48 h, suggesting that this potential is present within a narrow group of bacteria. This study sheds light on the functioning of the microbial community in the sulphur cycle of the Indian Ocean OMZs.

中文翻译：

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北印度洋最低氧区可培养硫氧化细菌的多样性

摘要 最低含氧区 (OMZ) 是全球海洋独特、广泛分布且研究充分的特征，其季节性和强度各不相同。北印度洋在阿拉伯海 (AS-OMZ) 和孟加拉湾 (BB-OMZ) 中包含具有独特生物地球化学特征的 OMZ。OMZ 水柱拥有独特的微生物群落，在海洋生物地球化学循环中起着至关重要的作用。OMZ 微生物群落促进的硫循环过程在空间和时间上对涉及的不同微生物群知之甚少。在这里，我们跨越溶解氧梯度对 AS-OMZ 和 BB-OMZ 中的不同站点进行采样，以使用改良的琼脂培养基获得可培养的硫氧化细菌 (SOB) 多样性。分离株的系统发育分析将它们中的大部分置于变形菌门中，其次是放线菌、厚壁菌门和拟杆菌门。分离株的硫代硫酸盐氧化电位分析显示，α-变形菌属、Citreicella thiooxidans 和 β-变形菌种、Achromobacter xylosoxydans 在 48 小时内将硫代硫酸盐氧化为硫酸盐，这表明这种电位存在于一小群细菌中。这项研究揭示了印度洋 OMZ 硫循环中微生物群落的功能。