Psychromonas profunda sp. nov., a psychropiezophilic bacterium from deep Atlantic sediments

Researchers isolated and characterized a novel bacterial species, Psychromonas profunda, from deep Atlantic sediments at 2770 meters depth and 2.7°C temperature. This Gram-negative rod bacterium is a strict psychrophile with optimal growth at 3-4°C and exhibits moderate piezophily, with maximum growth rate at 15-20 MPa pressure at 6°C. The strain's piezophilic response increases at higher temperatures, reaching optimal growth around 25 MPa at 10°C. Polyphasic analysis including 16S rRNA sequencing, DNA-DNA hybridization, fatty acid profiling, and phenotypic characterization confirmed this as a distinct species within the genus Psychromonas. The bacterium is facultatively anaerobic, oxidase-positive, and prototrophic except for possible vitamin dependency. Its G+C content is 38.1 mol%, lower than related Psychromonas species. DNA-DNA relatedness values below 40% with known Psychromonas species confirmed its novelty. P. profunda occupies an intermediate position in piezophily between the non-piezophilic P. antarctica and obligately piezophilic P. kaikoae, providing valuable material for studying enzyme adaptation to combined extreme conditions of cold and high pressure.

Key findings

• Psychromonas profunda is a novel psychropiezophilic bacterium isolated from deep Atlantic sediments, representing a new species with 38.1 mol% G+C content and <40% DNA-DNA relatedness to other Psychromonas species
• The strain exhibits optimal growth at 3-4°C under atmospheric pressure and moderate piezophily with maximum growth at 15-20 MPa at 6°C or 25 MPa at 10°C, intermediate between non-piezophilic P. antarctica and obligately piezophilic P. kaikoae
• P. profunda demonstrates increased piezophilic response when temperature increases, suggesting temperature and pressure affect enzyme function and membrane fluidity in offsetting ways
• The availability of closely related Psychromonas species adapted to different ocean depths provides a biological model for studying functional adaptation of cold-active enzymes across the piezosphere's hydrostatic pressure range