16SrRNA and enzymatic diversity of culturable bacteria from the sediments of oxygen minimum zone in the Arabian Sea

Abstract

Sediment underlying the oxygen minimum zone of the eastern Arabian Sea is rich in organic matter. Bacteria in this sediment-water interface are of great ecological importance as they are responsible for decomposing, mineralizing and subsequent recycling of organic matter. This study has for the first time addressed the phylogenetic and functional description of culturable bacteria of this region. Genotypic characterization of the isolates using amplified rDNA restriction analysis (ARDRA) followed by 16SrRNA sequencing grouped them into various phylogenetic groups such as Firmicutes, Gammaproteobacteria, Low G+C Gram positive bacteria, Actinobacteria and unaffiliated bacteria. Among the enzyme activities, phosphatase was predominant (52%) and was associated with all the phylotypes followed by amylase (37%) and gelatinase (33%). These hydrolytic enzymes were expressed at a wide range of temperature and pH. Firmicutes expressed most of the hydrolytic activities, consistent with a role in degradation of organic matter. Multiple enzyme expression (>/=3) was exhibited by Actinobacteria (100%), followed by unaffiliated group (62.5%) and Firmicutes (61.5%). Besides hydrolytic enzymes, the phylotypes also elaborated functional enzymes such as nitrate reductase and catalase (58 and 81% of the isolates, respectively). In the oxygen minimum zone, the diversity was high with 28 phylotypes. Culturable bacterial assemblages encountered were Bacillus sp., Halobacillus sp., Virgibacillus sp., Paenibacillus sp., Marinilactibacillus sp., Kytococcus sp., Micrococcus sp., Halomonas sp. and Alteromonas sp. The high diversity and high percentage of extracellular hydrolytic enzyme activities of the culturable bacteria reflect their important ecological role in biogeochemical cycling of organic matter in the oxygen minimum zone.

Isolation, diversity, and biotechnological potential of rhizo- and endophytic bacteria associated with mangrove plants from Saudi Arabia

“…Previous studies have also reported production of different hydrolases from marine bacteria belonging to genera Erwinia, Vibrio, Psychrobacter marinobacter, Chromohalobacter, Halomonas, Microbulbifer, and Alteromonas (Dalmaso et al, 2015), whereas the production of enzymes by marine Aidingimonas have not been previously reported. The second dominant phylum Firmicutes comprised of Bacillus, which has been reported as a dominant genus among all the marine enzyme-producing bacteria (Divya et al, 2010). This is because Bacillus is easy to culture and can endure harsh environmental conditions.…”

Evaluating the Diversity of Culturable Thermotolerant Bacteria from Four Hot Springs of India

“…At 90% similarity level, thermotolerant isolates from Bakreshwar, Balrampur, Chumathang and Vashist thermal springs grouped into 14, 14, 11 and 9 clusters respectively. ARDRA has been effectively utilized in the past for both culture dependent and culture independent diversity studies as a tool to group the isolates and clones into phylotypes [17][18][19].…”

“…The use of 16S rRNA gene sequencing in combination with ARDRA for grouping into phylogenetic clusters and identification of bacteria is well documented [18][19][20]. Although the number of phylogenetic clusters is less in Vashist, the average bacterial population was highest in Vashist and the lowest in Balrampur.…”

“…Restriction patterns can then be compared [17] and analysed using bioinformatic tools. The utility of ARDRA in genotypic characterization of bacteria [18] and screening clone libraries [19] for grouping them into phylogenetic clusters is undisputed. ARDRA has been utilized in the past for identification of bacteria up to species level also [20].…”

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

“…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.…”