16S rRNA-based bacterial diversity in the organic-rich sediments underlying oxygen-deficient waters of the eastern Arabian Sea

Abstract

The eastern Arabian Sea has a unique and permanent oxygen minimum zone (OMZ) that extends along the western continental margin of India. The sediment below this region is rich in organic matter. This study describes the bacterial community structure and diversity in OMZ sediments of the eastern Arabian Sea (AS) through 16S rRNA clone library analysis. Phylogenetic analysis of the sequences demonstrated that phylum Proteobacteria (52%), followed by Planctomycetes (12.7%), Chloroflexi and an unidentified bacterial group (8.8% each) were represented in the library. Deltaproteobacteria was the dominant class (62.5%) in phylum Proteobacteria with clones falling in orders Syntrophobacterales and Desulfovibrionales. Few minor phylogenetic groups, corresponding to Spirochetes, Firmicutes, Acidobacteria and Verrucomicrobia were found. Unidentified candidate groups falling in OP11, OP8 and OP3 were represented by 0.9, 2.9 and 3.9%, respectively and two clusters of the cloned sequences in this study showed very low identity to known sequences. This is the first report that discusses the phylogenetic groups in the OMZ sediments of eastern Arabian Sea individually and compares it with available data from marine hypoxic locales and water mass. LIBSHUFF statistics revealed high richness of the bacterial community of the Arabian Sea OMZ (AS-OMZ) compared to the other regions.

Bacterial diversity in the surface sediments of the hypoxic zone near the Changjiang Estuary and in the East China Sea

“…Cluster 2 included OTUs related to Phycisphaera mikurensis. More than 100 sequences from the O 2 -depleted stations were grouped into OTU228, which possessed 97% identity with an environmental clone from the organic-rich sediment underlying O 2deficient waters of the eastern Arabian Sea (Divya et al 2011). A few sequences in three OTUs within OM190 were distantly related to anammox-like environmental sequences in Cluster 3 (Fig.…”

Diversity and bioactive potentials of culturable heterotrophic bacteria from the surficial sediments of the Arabian Sea

“…The dominance of Firmicutes and γ-Proteobacteria in sediments of AS at 200, 500 and 1000 m depth of Goa coast was reported earlier (Divya et al 2010). Divya et al (2011) also confirmed the dominance of Proteobacteria in AS sediments by culture-independent clone library approach. Although the diversity of bacteria from different marine environments are reported, an ecological interpretation, including which group of bacteria are dominant in different environment (like oligotrophic, OMZ, vents, etc.…”

“…OMZ alters the chemical composition of the surrounding environment and also induce stress on the organisms (Childress and Sieibel 1998; Schneider and Bush-Brown 2003). Previous studies on OMZ have concentrated primarily on the diversity of microorganisms in these waters/sediments (Bryant et al 2012; Divya et al 2010, 2011) and their functional role in nitrogen cycle (Paulmier and Ruiz-Pino 2009). Though OMZ constitute only about 0.1% of the total oceanic volume, about 30–40% of the total oceanic nitrogen loss is estimated to occur within it.…”

Seasonal Variation of Bacterial Community in the Seawater of Gwangyang Bay Estimated by Amplified Ribosomal DNA Restriction Analysis

“…This observation was also obtained from the earlier study on the estimation of bacterial diversity of seawater in Gwangyang bay by phylogenetic analysis conducted by Kim [15] except the predominance of Firmicutes in spring. A research on 16S rRNA-based bacterial diversity in the organic-rich sediments underlying oxygen deficient waters of eastern Arabian Sea also revealed that Proteobacteria was the most prevalent phylum represented by both cultivable and non-culturable classes [6]. The predominant presence of Proteobacteria was also observed in all sea water samples collected from four different locations or habitat along the coast of the Red Sea in Saudi Arabia [19] and Yellow Sea, Korea [23].…”

“…The phylogeny of prokaryotes states that phylum Proteobacteria is of biological significance as it is the most dominant and diverse group of the microbial assemblage [9]. It has been reported that occurrence of classes of Proteobacteria in sediments was dominant in certain regions of water [6,16,31]. Class Alphaproteobacteria are frequently encountered in the marine habitats especially in the pelagic zone [11] and Gammaproteobacteria has been reported among culturable and non-culturable bacteria of pelagic waters [7,22].…”