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Summary: Viruses represent a driving force in the evolution of microorganisms including those thriving in extreme environments. However, our knowledge of the viral diversity associated to microorganisms inhabiting the deep‐sea hydrothermal vents remains limited. The phylum of Thermotogae, including thermophilic bacteria, is well represented in this environment. Only one virus was described in this phylum, MPV1 carried by Marinitoga piezophila. In this study, we report on the functional and genomic characterization of two new bacterioviruses that infect bacteria from the Marinitoga genus. Marinitoga camini virus 1 and 2 (MCV1 and MCV2) are temperate siphoviruses with a linear dsDNA genome of 53.4 kb and 50.5 kb respectively. Here, we present a comparative genomic analysis of the MCV1 and MCV2 viral genomes with that of MPV1. The results indicate that even if the host strains come from geographically distant sites, their genomes share numerous similarities. Interestingly, heavy metals did not induce viral production, instead the host of MCV1 produced membrane vesicles. This study highlights interaction of mobile genetic elements (MGE) with their hosts and the importance of including hosts‐MGEs' relationships in ecological studies. [ABSTRACT FROM AUTHOR]

Deep-sea hydrothermal vents are inhabited by complex communities of microbes and their viruses. Despite the importance of viruses in controlling the diversity, adaptation and evolution of their microbial hosts, to date, only eight bacterial and two archaeal viruses isolated from abyssal ecosystems have been described. Thus, our efforts focused on gaining new insights into viruses associated with deep-sea autotrophic archaea. Here, we provide the first evidence of an infection of hyperthermophilic methanogenic archaea by a head-tailed virus, Methanocaldococcus fervens tailed virus 1 (MFTV1). MFTV1 has an isometric head of 50 nm in diameter and a 150 nm-long non-contractile tail. Virions are released continuously without causing a sudden drop in host growth. MFTV1 infects Methanocaldococcus species and is the first hyperthermophilic head-tailed virus described thus far. The viral genome is a double-stranded linear DNA of 31 kb. Interestingly, our results suggest potential strategies adopted by the plasmid pMEFER01, carried by M. fervens, to spread horizontally in hyperthermophilic methanogens. The data presented here open a new window of understanding on how the abyssal mobilome interacts with hyperthermophilic marine archaea., (© 2020 Society for Applied Microbiology and John Wiley & Sons Ltd.)

Trillions of microorganisms, termed the "microbiota", reside in the mammalian gastrointestinal tract, and collectively participate in regulating the host phenotype. It is now clear that the gut microbiota, metabolites, and intestinal immune function are correlated, and that alterations of the complex and dynamic host-microbiota interactions can have deep consequences for host health. However, the mechanisms by which the immune system regulates the microbiota and by which the microbiota shapes host immunity are still not fully understood. This article discusses the contribution of metabolites in the crosstalk between gut microbiota and immune cells. The identification of key metabolites having a causal effect on immune responses and of the mechanisms involved can contribute to a deeper insight into host-microorganism relationships. This will allow a better understanding of the correlation between dysbiosis, microbial-based dysmetabolism, and pathogenesis, thus creating opportunities to develop microbiota-based therapeutics to improve human health. In particular, we systematically review the role of soluble and membrane-bound microbial metabolites in modulating host immunity in the gut, and of immune cells-derived metabolites affecting the microbiota, while discussing evidence of the bidirectional impact of this crosstalk. Furthermore, we discuss the potential strategies to hear the sound of such metabolite-mediated crosstalk.

Viruses represent a driving force in the evolution of microorganisms including those thriving in extreme environments. However, our knowledge of the viral diversity associated to microorganisms inhabiting the deep-sea hydrothermal vents remains limited. The phylum of Thermotogae, including thermophilic bacteria, is well represented in this environment. Only one virus was described in this phylum, MPV1 carried by Marinitoga piezophila. In this study, we report on the functional and genomic characterization of two new bacterioviruses that infect bacteria from the Marinitoga genus. Marinitoga camini virus 1 and 2 (MCV1 and MCV2) are temperate siphoviruses with a linear dsDNA genome of 53.4 kb and 50.5 kb respectively. Here, we present a comparative genomic analysis of the MCV1 and MCV2 viral genomes with that of MPV1. The results indicate that even if the host strains come from geographically distant sites, their genomes share numerous similarities. Interestingly, heavy metals did not induce viral production, instead the host of MCV1 produced membrane vesicles. This study highlights interaction of mobile genetic elements (MGE) with their hosts and the importance of including hosts-MGEs' relationships in ecological studies., (© 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.)