Temperature and pressure adaptation of a sulfate reducer from the deep subsurface

Abstract

Microbial life in deep marine subsurface faces increasing temperatures and hydrostatic pressure with depth. In this study, we have examined growth characteristics and temperature-related adaptation of the Desulfovibrio indonesiensis strain P23 to the in situ pressure of 30 MPa. The strain originates from the deep subsurface of the eastern flank of the Juan de Fuca Ridge (IODP Site U1301). The organism was isolated at 20°C and atmospheric pressure from ~61°C-warm sediments approximately 5 m above the sediment–basement interface. In comparison to standard laboratory conditions (20°C and 0.1 MPa), faster growth was recorded when incubated at in situ pressure and high temperature (45°C), while cell filamentation was induced by further compression. The maximum growth temperature shifted from 48°C at atmospheric pressure to 50°C under high-pressure conditions. Complementary cellular lipid analyses revealed a two-step response of membrane viscosity to increasing temperature with an exchange of unsaturated by saturated fatty acids and subsequent change from branched to unbranched alkyl moieties. While temperature had a stronger effect on the degree of fatty acid saturation and restructuring of main phospholipids, pressure mainly affected branching and length of side chains. The simultaneous decrease of temperature and pressure to ambient laboratory conditions allowed the cultivation of our moderately thermophilic strain. This may in turn be one key to a successful isolation of microorganisms from the deep subsurface adapted to high temperature and pressure.

Microbial Sulfate Reduction Potential in Coal-Bearing Sediments Down to ~2.5 km below the Seafloor off Shimokita Peninsula, Japan

“…Increasing pressure affects e.g., motility, cell division, DNA replication, transcription, translation, or certain enzymatic reactions (Marietou and Bartlett, 2014 ) and increasing temperature has recently been shown to increase damage of cell walls and DNA by protein racemization and DNA depurination reactions (Lever et al, 2015 ). In a recent study, sulfate reducers isolated from deep and hot (~60°C, 30 MPa) sediments at the Juan de Fuca Ridge showed adaptation to the increased pressure and temperature e.g., by exchanged membrane lipid composition and an increase of their optimum growth temperature (Fichtel et al, 2015 ).…”

Seawater recirculation through subducting sediments sustains a deeply buried population of sulfate‐reducing bacteria

“…Fichtel et al. (, ) investigated a microbial community residing above a ridge flank SBI with known sulfate diffusion. They suggested that 30–40 m of hemipelagic clay overlying the basement could act as a hydrogeological barrier for advective fluid flow, and therefore, stop the transportation of particles such as microbial cells.…”

“…Desulfovibrionales have been cultured from a variety of subsurface environments (e.g., Magot, Basso, Tardy‐Jacquenod, & Caumette, ; Pedersen, Arlinger, Ekendahl, & Hallbeck, ; Sass & Cypionka, ) with in situ temperatures >60°C (Bale et al., ; Fichtel et al., ), exceeding their optimum growth temperature of ~40°C. Cores 322‐C0012A‐29R to 322‐C0012A‐56R (313 mbsf–554 mbsf) were obtained from depths with in situ temperatures of 40–63°C (Henry et al., ).…”

“…Spore-forming bacteria were present in the total 16S rRNA gene library (Supporting Information Figure S3); however, these taxa showed no close phylogenetic relationship to SRB, except for Desulfosporosinus (0.04% relative abundance of total 16S rRNA gene-based SRB taxa). Fichtel et al (2012Fichtel et al ( , 2015 investigated a microbial community residing above a ridge flank SBI with known sulfate diffusion. They suggested that 30-40 m of hemipelagic clay overlying the basement could act as a hydrogeological barrier for advective fluid flow, and therefore, stop the transportation of particles such as microbial cells.…”

Utilizing Lipid Biomarkers to Understand the Microbial Community Structure of Deep Subsurface Black Shale Formations

“…For example, we do not yet know the in situ microbial survival mechanisms in the subsurface and how they have been/were affected by the prevailing geologic and environmental conditions. It is also difficult to establish whether the microbes detected in the deep subsurface represent environmental conditions at the time of deposition or if they reflect changes that took place after deposition (Fredrickson et al, 1995b;1997;Fichtel et al, 2015;Inagaki et al, 2015). This is further complicated by the fact that drilling and fracturing fluids used during development, introduces large quantities of labile carbon, nutrients, and exogenous organisms into the subsurface Lester et al, 2015;Gaspar et al, 2014;) making it unclear whether indigenous communities exist in these shale formations.…”