| Deep-sea hydrothermal ventisone ofthe most extreme environments on earth. Since its first discovery in 1977, deep-sea hydrothermal vent ecosystem has been widely concerned by marine scientists, and becomesa hotspot in marine biology and ecology. Chemoautotrophic archaea and bacteria use thermal and chemical energy to synthesize organic matters, supplying nutrientsfor other hydrothermal organisms. As the basis of deep-seavent ecosystem, microorganisms can regulate the vent biological communities. Previous studies have been found that virusesare abundant in hydrothermal vents, suggesting that viruses maybe essential players in the deep-sea vent ecosystems. Therefore, the interactions between the vent virus and microorganismare very important forrealizing the deep-seavent ecosystems.The dynamic changes of temperature and chemical gradients in deep-sea hydrothermal vents may influence the vent microbial community structure and abundance. In this study, the bacterial communities of the vent sulfide,seawater and tubeworm trophosome from East Pacific Rise, South Atlantic Ridge and Southwest Indian Ridge were firstly characterized. The analysis of bacterial 16S rRNA sequencesshowed that Proteobacteria, Actinobacteria and Bacteroideteswere the predominant phyla in all vents.However,thedifferences of bacterial diversity were observed among different vents from three oceanic regions.The sulfides ofEast Pacific Rise possessedthe mostdiversebacterial communities. The bacterial diversities of vent seawater were much lower than those of vent sulfides. The symbiotic bacteria of tubeworm Ridgeia piscesaewere included in the bacterial community of vent sulfides, suggesting their significant ecological functions as the primary producers in the deep-sea hydrothermal vent ecosystems.Therefore, our study presented a comprehensive view ofbacterial communities in deep-sea hydrothermal vents from different oceans.The results indicated that the bacterial communities in the hydrothermal vents from different oceans were various, suggesting that viruses might play important roles in bacterial communities. Therefore,the virus-microbe interactions in deep-sea hydrothermal vent were explored. To obtain the metagenomic DNA of deep-sea vent viruses, the efficient strategies for the isolation of vent virions and the extraction of virus metagenomic DNA were investigated. The results revealed that the virus metagenomic DNA of the isolated virions from deep-sea vent could be used for high-throughput sequencing. Therefore, an efficient method for the isolation of vent virions and the extraction of virus metagenomic DNAwas established in this study. Using the improved virus isolation and metagenomic DNA extraction method, the viral and microbial metagenomes of deep-sea hydrothermal vent were analyzed.The results showed that the classification of viral functional genes was similar to that of microbial functional genes in deep-sea hydrothermal vents. The genes involved inamino acid transport and metabolism, transcription, inorganic ions transport and metabolism, cell membrane and cell wall metabolism, energy production and transformation accouted for higher proportions in theviral and microbial metagenomes. It was revealed that the virus could encode the protins related to host lysis, including transglycosylase, dipeptidase and N-acetylmuramoyl-L-alanine amidase. The findings suggested that viruses could lyse microorganisms in deep-sea hydrothermal vents. The analysis of KEGG pathwaysindicated that the viral genes were involved in themicrobial metabolic processes.Some viral genes, such as glucokinase, 6-phosphofructokinase 1, hydroxyacyl glutathione hydrolase, D-lactate dehydrogenase, acetate kinase and aldehyde dehydrogenasegenes took compensation effectsonthemicrobial metabolic processes. The results revealed that the viral genes improved the microbial metabolism, leading to the enhancement of microorganism’s suitability in the deep-sea vent ecosystems. These findings presented that viruses could regulate the structures and metabolism of microorganisms and further took great effects on the deep-sea vent ecosystems.The findings indicated that the virus infection could change the metabolism of its host microorganisms. Themetabolic changes were similar to the metabolic processes of tumors during tumorigenesis. Thus,on the basis of previous studies, the secondary metabolites of Geobacillus sp. E263, a thermopile from deep-sea hydrothermal vent, in response to its bacteriophage GVE2 infectionwere screened for the anti-tumor compounds.The results showed that among the 6 compounds with known structure (L-norleucine,2-Amino-4-methylphenol,4-Hydroxybenzyl alcohol, tryptophol, adenine and antipyrine), L-norleucine could significantly inhibit thecell proliferation, migration, invasion and adhesion of gastric cancer cell HGC-27 and breast cancer cell MDA-MB-435. But L-norleucine had no effect on theproliferation of normal gastric and breast cells. Our study presented that L-norleucineexhibited the activity of anti-tumor metastasis.Based on the analysis of anti-tumor activity of L-norleucine analogues, the active group of L-norleucine was identified. After derivatization of L-norleucine and the anti-tumor assays using L-norleucine derivants, it was found that (3 s,6 s)-3,6-dibutyl piperazine-2,5-diketone could inhibit the cancer cell metastasis. The further investigations showed that L-norleucine exhibited its activity of anti-tumor metastasisby interacting with hnRNPA2/B1 protein and upregulating the E-cadherin expression.This study focused on the virus-microorganism interactions in deep-sea hydrothermal vent. The findings onthe diversities of bacterial communities from East Pacific Rise, South Atlantic Ridge and Southwest Indian Ridge expanded our understanding of the microbial communitiesin deep-sea hydrothermal vents.The subsequent investigations on the microbial and viral metagenomes revealed that viruses played very important roles in regulating the deep-sea vent microbial communities. Based on the analysis of the secondary metabolites of bacteriophage GVE2-infected Geobacillus sp. E263, L-norleucine exhibited the activity of anti-tumor metastasis. In this context, our findings provided novel insights into the virus-micriobe interactions and the microbial resourcesin deep-sea hydrothermal vents. |
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