Environmental Adaptation And Genetic Resources Discovery Of A Deep-sea Hydrothermal Vent Chimney Microbial Community

Deep-sea hydrothermal vent chimneys that form by interactions between hot fluids and cold seawater are regarded as primordial environments reminiscent of early Earth conditions, with reactive gases, dissolved elements, and thermal and chemical gradients operating over spatial scales of millimeters and centimeters up to meters. These chemical and thermal gradients along and inside the sulfide chimneys provide a wide range of microhabitats for chemolithoautotrophic microorganisms that fix inorganic carbon using chemical energy obtained through the oxidation of reduced inorganic compounds contained in the hydrothermal fluids, converting the geothermally derived energy into microbial biomass. Although the phylogenetic diversity of these microorganisms has been described previously, the adaptation and metabolic potential of the microbial communities is only beginning to be revealed. A pyrosequencing approach was utilized to directly obtain sequences from a fosmid library constructed from a black smoker chimney 4143-1 in the Mothra hydrothermal vent field at the Juan de Fuca Ridge. A total of 308,034 reads with an average sequence length of 227 bp were generated. The sequenced microbiome of the hydrothermal vent sample consisted of 31,405 contigs and 22,968 singletons, a total of 15.3 MB. A total of 21,836 open reading frames (ORFs) were predicted from the data set, more than 70% of which could be classified into function sets in the COG category.Firstly, comparative genomic analyses of metagenomes from a variety of environments by two-way clustering of samples and functional gene categories demonstrated that the 4143-1 metagenome clustered most closely with that from a carbonate chimney from Lost City; both are highly enriched in genes for mismatch repair and homologous recombination, suggesting that the microbial communities have evolved extensive DNA repair systems to cope with the extreme conditions that have potential deleterious effects on the genomes. As previously reported for the Lost City microbiome, the metagenome of chimney 4143-1 exhibited a high proportion of transposases, implying that horizontal gene transfer may be a common occurrence in the deep-sea vent chimney biosphere. In addition, genes for chemotaxis and flagellar assembly were highly enriched in the chimney metagenomes, reflecting the adaptation of the organisms to the highly dynamic conditions present within the chimney walls.Secondly, we reconstruct the metabolic pathways at the metegenome level. The result indicated that the microbial community in the wall of chimney 4143-1 was mainly fueled by sulfur oxidation through sulfur-compound oxidation (sox) dependent and adenosine-5'-phosphosulfate (APS) dependent pathways, putatively coupled to nitrate reduction to perform inorganic carbon fixation through the Calvin-Benson-Bassham cycle (CBB cycle). Based on the genomic organization of the key genes of the carbon fixation and sulfur oxidation pathways contained in the large genomic fragments, both obligate and facultative autotrophs appear to be present and contributing to biomass production.Then, we screened the library with specific primers and got two fomsid containing PKS/NPRS gene fragments. Although neither of them had antimicrobial functions towards Escherichia coli, Bacillus subtilis or Saccharomyces cerevisiae. There are some characters of the two PKS/NPRS clusters, which are different from knows.In summary, in addition to the understanding of novel mechanism for the formation of such unique environment driven by this special community of microbiota, the genetic resources from the deep-sea vent environments will be available for further functional analyses as gene treasure house through this novel approach.