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Physiological and gene expression studies of deep-sea bacteria under pressure conditions similar to those experienced in their natural habitat are critical for understanding growth kinetics and metabolic adaptations to in situ conditions. The Campylobacterium (aka Epsilonproteobacterium) Nautilia sp. strain PV-1 was isolated from hydrothermal fluids released from an active deep-sea hydrothermal vent at 9° N on the East Pacific Rise. Strain PV-1 is a piezophilic, moderately thermophilic, chemolithoautotrophic anaerobe that conserves energy by coupling the oxidation of hydrogen to the reduction of nitrate or elemental sulfur. Using a high-pressure-high temperature continuous culture system, we established that strain PV-1 has the shortest generation time of all known piezophilic bacteria and we investigated its protein expression pattern in response to different hydrostatic pressure regimes. Proteogenomic analyses of strain PV-1 grown at 20 and 5 MPa showed that pressure adaptation is not restricted to stress response or homeoviscous adaptation but extends to enzymes involved in central metabolic pathways. Protein synthesis, motility, transport, and energy metabolism are all affected by pressure, although to different extents. In strain PV-1, low-pressure conditions induce the synthesis of phage-related proteins and an overexpression of enzymes involved in carbon fixation.

This study delves into the genomic features of 10 Vibrio strains collected from deep-sea hydrothermal vents in the Pacific Ocean, providing insights into their evolutionary history and ecological adaptations. Through sequencing and pan-genome analysis involving 141 Vibrio species, we found that deep-sea strains exhibit larger genomes with unique gene distributions, suggesting adaptation to the vent environment. The phylogenomic reconstruction of the investigated isolates revealed the presence of 2 main clades: The first is monophyletic, consisting exclusively of Vibrio alginolyticus , while the second forms a monophyletic clade comprising both Vibrio antiquarius and Vibrio diabolicus species, which were previously isolated from deep-sea vents. All strains carry virulence and antibiotic resistance genes related to those found in human pathogenic Vibrio species which may play a wider ecological role other than host infection in these environments. In addition, functional genomic analysis identified genes potentially related to deep-sea survival and stress response, alongside candidate genes encoding for novel antimicrobial agents. Ultimately, the pan-genome we generated represents a valuable resource for future studies investigating the taxonomy, evolution, and ecology of Vibrio species. [ABSTRACT FROM AUTHOR]

Varunaivibrio sulfuroxidans type strain TC8T is a mesophilic, facultatively anaerobic, facultatively chemolithoautotrophic alphaproteobacterium isolated from a sulfidic shallow-water marine gas vent located at Tor Caldara, Tyrrhenian Sea, Italy. V. sulfuroxidans belongs to the family Thalassospiraceae within the Alphaproteobacteria, with Magnetovibrio blakemorei as its closest relative. The genome of V. sulfuroxidans encodes the genes involved in sulfur, thiosulfate and sulfide oxidation, as well as nitrate and oxygen respiration. The genome encodes the genes involved in carbon fixation via the Calvin–Benson–Bassham cycle, in addition to genes involved in glycolysis and the TCA cycle, indicating a mixotrophic lifestyle. Genes involved in the detoxification of mercury and arsenate are also present. The genome also encodes a complete flagellar complex, one intact prophage and one CRISPR, as well as a putative DNA uptake mechanism mediated by the type IVc (aka Tad pilus) secretion system. Overall, the genome of Varunaivibrio sulfuroxidans highlights the organism's metabolic versatility, a characteristic that makes this strain well-adapted to the dynamic environmental conditions of sulfidic gas vents. [ABSTRACT FROM AUTHOR]

ABSTRACT Between October 2005 and March 2006, a seafloor volcanic eruption occurred at 9°50'N East Pacific Rise (EPR), establishing a 'time zero' for characterizing newly-formed hydrothermal vent habitats and comparing [...]

ABSTRACT In April 1991, submarine volcanic eruptions initiated the formation of numerous hydrothermal vents between 9°45' and 9°52'N along the crest of the East Pacific Rise (EPR). Dramatic changes in [...]

The vertical distribution of bacteriochlorophyll a, the numbers of infrared fluorescent cells, and the variable fluorescence signal at 880 nanometers wavelength, all indicate that photosynthetically competent anoxygenic phototrophic bacteria are abundant in the upper open ocean and comprise at least 11% of the total microbial community. These organisms are facultative photoheterotrophs, metabolizing organic carbon when available, but are capable of photosynthetic light utilization when organic carbon is scarce. They are globally distributed in the euphotic zone and represent a hitherto unrecognized component of the marine microbial community that appears to be critical to the cycling of both organic and inorganic carbon in the ocean., Although closely related to purple photosynthetic bacteria, aerobic anoxygenic photoheterotrophs (AAPs) are obligate aerobes, with unusually high concentrations of carotenoids (1-3), low cellular contents of bacteriochlorophyll a (BChla) (4), and [...]

Phylogenetic characterization and population structure of marine benthic archaea in deep-sea sediments are discussed. These microbes are important in marine picoplankton assemblages. A complex archaeal population structure was found by phylogenetic analysis of rDNA sequences. Significant depth-related variability in the population was seen.

The high levels of mercury resistance merA to Hg (II) found in bacteria isolated form the interface between hydrothermal fluids and oxygenated seawater is studied. The distribution of mercury resistance among the deep-sea strains studied clearly showed that mesophilic and moderately thermophilic strains from the vent and its associated plume were more resistant to Hg(II) than psychrophilic strains collected at the control side.

Biomass samples from the Black Sea were analyzed for SSU genes from Bacteria and Archaea after ten years of storage at -80 degrees Celsius and both clonal libraries and fingerprinting by terminal restriction fragment length polymorphism analyses were used to assess the microbial community. Of the clones obtained, an epsilon-Proteobacteria and a Pseudoalteromonas-like clone accounted for major peaks in the fingerprint, while deeply branching lineages were associated with smaller peaks.