Bacterial and archaeal communities in deep sea waters near the Ninetyeast Ridge in Indian Ocean

Depth-dependent distribution patterns of bacterial and archaeal communities in deep sea water column around the Ninetyeast Ridge in the Indian Ocean were investigated using 16S rRNA gene profiling.Sampling was conducted at the northern Ninetyeast Ridge(1°59.89′N–9°59.70′S,87°58.90′E–88°00.03′E)from September to November 2016 where samples were collected from the bathyal(1000 m)to bathypelagic depths(>4000 m)in four different stations.A total of 1565405 clean data falling into 6712 bacterial OTUs and 1452727 clean data falling into 806 archaeal OTUs based on 97%similarity level were analyzed.Most of the bacterial 16S rRNA gene sequences were affiliated with Gammaproteobacteria,followed by Alphaproteobacteria and Bacteroidia.The archaeal 16S rRNA gene sequences mostly affiliated to Nitrososphaeria(Thaumarchaeota)dominated with relative abundances ranging from 52.68%to 97.2%,followed by Thermoplasmata(Euryarchaeota).Vertical partitioning of bacterial and archaeal communities among different water layers was observed.Canonical correspondence analysis(CCA)and Spearman’s correlations revealed that depth(P=0.003),dissolved oxygen(P=0.019),and nitrite(P=0.033)were the main environmental factors affecting bacterial community structure at genus level in the Ninetyeast Ridge.On the other hand,the first two CCA axes accounted for 74.4%of the explained total variance,it seems that the archaeal communities at genus level were heavily influenced by the environmental variables including depth,dissolved oxygen(DO),nitrite,salinity,phosphate,ammonia,nitrate,and silicate,but none of them exhibited any significant correlation on the structuring(P>0.1).

Integration of metabolomics and transcriptomics revealed the biosynthetic mechanism of anti-parasitic compounds in Salinivibrio proteolyticus strain YCSC6

The fermentation broth of Salinivibrio proteolyticus strain YCSC6 shows potent anti-parasitic activity against Uronema marinum,with activity varying in each fermentation stage.To investigate the biosynthetic mechanism of anti-parasitic compounds in strain YCSC6,a comprehensive analysis of metabolomics and transcriptomics over four diff erent time points(12,24,48,and 72 h)was performed.Metabolomics detected 17943 metabolites with 1129 known metabolites.A trend analysis of the known metabolites showed that 575 metabolites,including 69 polyketides,were continuously enhanced,being the potential source of anti-parasitic agents.In addition,941 genes mapped to the same pathways of these metabolites,were screened through the association analysis of metabolites and genes.KEGG pathway enrichment of these genes showed 270 genes mapped to the biosynthesis of secondary metabolites and 192 genes mapped to the biosynthesis of antibiotics.This demonstrates the potent secondary metabolic capacity of strain YCSC6.Finally,a gene-metabolite correlation network was created based on the 575 continuously enhanced metabolites and 43 continuously up-regulated genes.This revealed 13 genes at the key position that mapped to a putative metabolic pathway associated with the biosynthesis of polyketides and caprylic acid,which contributes to the potent anti-parasitic activity of strain YCSC6.This comprehensive analysis of metabolomics and transcriptomics provides insights into the biosynthetic mechanisms of anti-parasitic compounds in strain YCSC6 and guides the exploitation of more anti-parasitic agents for aquaculture.