Abstract
Microorganisms living in deep-oil reservoirs face extreme conditions of elevated temperature and hydrostatic pressure. Within these microbial communities, members of the order Thermotogales are predominant. Among them, the genus Pseudothermotoga is widespread in oilfield-produced waters. The growth and cell phenotypes under hydrostatic pressures ranging from 0.1 to 50 MPa of two strains from the same species originating from subsurface, Pseudothermotoga elfii DSM9442 isolated from a deep African oil-producing well, and surface, P. elfii subsp. lettingae isolated from a thermophilic sulfate-reducing bioreactor, environments are reported for the first time. The data support evidence for the piezophilic nature of P. elfii DSM9442, with an optimal hydrostatic pressure for growth of 20 MPa and an upper limit of 40 MPa, and the piezotolerance of P. elfii subsp. lettingae with growth occurring up to 20 MPa only. Under the experimental conditions, both strains produce mostly acetate and propionate as volatile fatty acids with slight variations with respect to the hydrostatic pressure for P. elfii DSM9442. The data show that the metabolism of P. elfii DSM9442 is optimized when grown at 20 MPa, in agreement with its piezophilic nature. Both Pseudothermotoga strains form chained cells when the hydrostatic pressure increases, especially P. elfii DSM9442 for which 44% of cells is chained when grown at 40 MPa. The viability of the chained cells increases with the increase in the hydrostatic pressure, indicating that chain formation is a protective mechanism for P. elfii DSM9442.
Highlights
The organisms growing preferentially under a hydrostatic pressure higher than the atmospheric pressure are called “piezophiles” (Zobell and Johnson, 1949; Yayanos, 1995)
A pressure-resistant terminal oxidase was discovered in Shewanella violacea (Tamegai et al, 2011); a piezophilic bioluminescent bacterium isolated at a 2,200 m water depth, Photobacterium phosphoreum ANT-2200, exhibits higher bioluminescence under high hydrostatic pressure than at atmospheric pressure (Martini et al, 2013) while no change at the transcriptional level of the light-emission involved genes can be detected (Tanet et al, 2019); and in the anaerobic sulfate-reducing bacterium D. piezophilus, transcriptomic and biochemical analyses have shown that metabolite cycling (H2/Formate) is an important mechanism required for energy conservation at high hydrostatic pressure (26 MPa; Pradel et al, 2013; Amrani et al, 2016)
Cultures of P. elfii DSM9442 at 0.1, 10, 20, 25, 30, 35, 40, and 50 MPa at 65°C revealed that this strain was able to grow up to 40 MPa, with no growth observed at 50 MPa after 5 days of incubation
Summary
The organisms growing preferentially under a hydrostatic pressure higher than the atmospheric pressure are called “piezophiles” (Zobell and Johnson, 1949; Yayanos, 1995). A pressure-resistant terminal oxidase was discovered in Shewanella violacea (Tamegai et al, 2011); a piezophilic bioluminescent bacterium isolated at a 2,200 m water depth, Photobacterium phosphoreum ANT-2200, exhibits higher bioluminescence under high hydrostatic pressure than at atmospheric pressure (Martini et al, 2013) while no change at the transcriptional level of the light-emission involved genes can be detected (Tanet et al, 2019); and in the anaerobic sulfate-reducing bacterium D. piezophilus, transcriptomic and biochemical analyses have shown that metabolite cycling (H2/Formate) is an important mechanism required for energy conservation at high hydrostatic pressure (26 MPa; Pradel et al, 2013; Amrani et al, 2016) Because these strategies have been identified by biochemical and genomic studies performed on cultured piezophilic strains, they yield a fragmented view on the adaptive mechanisms in piezophiles. One might expect that among the diverse and uncultured species of the deep biosphere, other unique and so-far unknown metabolic and physiological strategies to cope with elevated hydrostatic pressure are yet to be discovered (Cario et al, 2019)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
