Phylogenetic diversity of culturable marine bacteria from sediments underlying the oxygen minimum zone of the Arabian Sea and their role in nitrate reduction

Abstract

The dissolved oxygen concentration in ocean water is the main driver of nutrient and energy flow patterns within marine ecosystems (Diaz & Rosenberg, 2008;Diaz et al., 2009). Oxygen deficiency in ocean water selects for microbial groups capable of utilizing alternative respiratory substrates including nitrate, nitrite, sulfate, or carbon dioxide (Zehnder & Stumm, 1988). Within oxygen-deficient waters, the use of nitrite or nitrate as alternative electron acceptors results in the production of nitrous oxide and nitrogen gas (Lam & Kuypers, 2011). This leads to denitrification or loss of fixed nitrogen.The Arabian Sea (AS) oxygen minimum zone (OMZ) is one of the largest pelagic low-oxygen environments in the open ocean, which is a major part of global ocean-led denitrification, which extends from ~100 to 1,200 m of depth (Jayakumar et al., 2009). Here the oxygen concentration drops to 0.1 ml/L (4.5 μmol/kg) or lower, compared to the average ocean dissolved oxygen concentration that ranges between 6 and 8 ml/L (270-360 μmol/kg). These OMZ regions are of microbiological importance as major biogeochemical processes are catalyzed by the microbial communities which inhabit them

Elucidating the functional profiles of cultivable bacterial communities in the water and sediments during the southwest monsoon season, along the west coast of India

“…Previous studies have consistently identified the phyla Proteobacteria, Firmicutes, and Actinobacteria as the predominant bacterial groups in this region. This finding further supports the notion that these phyla play a crucial role in shaping the bacterial composition and dynamics within the productive upwelling zone of the Arabian Sea (Amberkar et al 2021;Parab et al 2022). Firmicutes contributed maximum during the monsoon season showing an abundance of 71% each in both water and sediment.…”

Diversity and Quantitative Detection of Clade I Type <i>nosZ</i> Denitrifiers in the Arabian Sea Oxygen Minimum Zone

“…Proteobacteria have been identified as the dominant phylum and play a significant role in denitrification in the AS-OMZ (Bandekar et al, 2018a;Gomes et al, 2018). OTUs obtained from the ASTS aligned into three classes: Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria, which is consistent with findings from the OMZ of the Subtropical Deep Reservoir (Zheng et al, 2014) and sediments of the AS (Amberkar et al, 2021). nosZ denitrifiers from the present study were predominant within the class Alphaproteobacteria, which is in accordance with the findings of Wyman et al (2013) from the AS.…”

Microbial Ecology of Oxygen Minimum Zones Amidst Ocean Deoxygenation

“…The redox conditions of OMZs are often favorable for processes in the nitrogen cycle such as denitrification and anammox as well as other important processes in the sulfur and methane cycles. These redox conditions are reflected in the organisms present in OMZs such as known nitrogen and sulfur cycling organisms like genera belonging to Candidatus Scalindua, Caulobacteriaceae, Pelagibacteriaceae, α-Proteobacteria, δ-Proteobacteria, and γ-Proteobacteria in the Arabian Sea and Bay of Bengal (Bandekar et al, 2018a,b;Rajpathak et al, 2018;Fernandes et al, 2019Fernandes et al, , 2020Amberkar et al, 2021), the Gulf of Alaska (Muck et al, 2019), Cariaco Basin (Madrid et al, 2001;Lin et al, 2008;Rodriguez-Mora et al, 2013Cernadas-Martín et al, 2017), the ETSP (Stevens and Ulloa, 2008;Bryant et al, 2012), the ETNP (Podlaska et al, 2012;Beman and Carolan, 2013;Beman et al, 2020;Pajares et al, 2020), and Saanich Inlet (Zaikova et al, 2010;Walsh and Hallam, 2011;Torres-Beltrán et al, 2019). The contribution of prokaryotes identified in OMZs to biogeochemical cycles has global ramifications and has thus been well-studied throughout previous decades and remains a highly active research endeavor.…”

“…The role of sediments in nutrient cycling extends to the nitrogen cycle as nitrification, denitrification, anammox, and DNRA all occur in the ETSP, where the sediments contribute to a net loss of N where the bottom waters are anoxic or nearly anoxic (Bohlen et al, 2011). Denitrifiers are also found in the sediments underlying the Arabian Sea (Lincy and Manohar, 2020;Amberkar et al, 2021), the Bay of Bengal (Lincy and Manohar, 2020), and the ETNP (Liu et al, 2003). Even the sediments in less intense OMZs, such as the NESAP, can greatly contribute to N 2 O production from denitrification and is largely modulated by the oxygen concentration of bottom waters (Jameson et al, 2021).…”

“…Even the sediments in less intense OMZs, such as the NESAP, can greatly contribute to N 2 O production from denitrification and is largely modulated by the oxygen concentration of bottom waters (Jameson et al, 2021). Likewise, the effect of low bottom water oxygen concentrations is felt by the prokaryotic communities as well, with different microbes occurring in sediments with oxic bottom waters compared to those with anoxic bottom waters (e.g., Divya et al, 2011;Divya, 2017;Besseling et al, 2018;Bhattacharya et al, 2020;Lincy and Manohar, 2020;Amberkar et al, 2021). Unfortunately, there have been no studies characterizing the community composition of viruses in sediment underlying marine OMZs.…”