Rhodothermus bifroesti sp. nov., a thermophilic bacterium isolated from the basaltic subsurface of the volcanic island Surtsey

Abstract

Novel thermophilic heterotrophic bacteria were isolated from the subsurface of the volcanic island Surtsey off the south coast of Iceland. The strains were isolated from tephra core and borehole fluid samples collected below 70 m depth. The Gram-negative bacteria were rod-shaped (0.3–0.4 µm wide, 1.5–7 µm long), aerobic, non-sporulating and non-motile. Optimal growth was observed at 70 °C, at pH 7–7.5 and with 1% NaCl. Phylogenetic analysis identified the strains as members of the genus Rhodothermus . The type strain, ISCAR-7401T, was genetically distinct from its closest relatives Rhodothermus marinus DSM 4252T and Rhodothermus profundi PRI 2902T based on 16S rRNA gene sequence similarity (95.81 and 96.01%, respectively), genomic average nucleotide identity (73.73 and 72.61%, respectively) and digital DNA–DNA hybridization (17.6 and 16.9%, respectively). The major fatty acids of ISCAR-7401T were iso-C17:0, anteiso-C15:0, anteiso-C17:0 and iso-C15:0 (>10 %). The major isoprenoid quinone was MK-7 while phosphatidylethanolamine, diphosphatidylglycerol, an unidentified aminophospholipid and a phospholipid were the predominant polar lipid components. Based on comparative chemotaxonomic, genomic and phylogenetic analyses, we propose that the isolated strain represents a novel species of the genus Rhodothermus with the name Rhodothermus bifroesti sp. nov. The type strain is ISCAR-7401T (=DSM 112103T=CIP 111906T).

Culturable Bacterial Diversity from the Basaltic Subsurface of the Young Volcanic Island of Surtsey, Iceland

“…Most of the isolates were aerobic and heterotrophic bacteria, and few novel species were isolated. In this perspective, a bacterium isolated in this study, Rhodothermus bifroesti, has been characterized [56]. The comparison of our cultured strains and ASVs from 16S rRNA amplicon gene datasets obtained from the same samples [37] revealed that isolates were detected using both culture-dependent (isolation) and -independent methods (metabarcoding).…”

“…The closest neighbor sequences corresponded to uncultured Rhodothermus species detected in seawater (EU249949) and Rubrobacter xylanophilus DSM 9941 isolated from hot spring water samples (CP000386) (Figure 2). The novel strains of Rhodothermus were characterized, and the name Rhodothermus bifroesti was attributed to the new species [56]. In addition, other isolated strains potentially represent novel species.…”

Co-isolation ofPenicillium citrinumand its cell-switching partnerMeyerozyma guilliermondiifrom a geothermal power plant

“…One example of these underexplored extreme environments is deep subsurface geothermal reservoirs used either for heating or for electricity production. Microbial strains isolated from these deep subsurface geothermal fluids include diverse bacterial species such as Thermus thermophilus TMY [16], Anoxybacillus geothermalis [17], [18], and Rhodothermus bifroesti [19], and archaeal strains including Pyrobacurum [20] or Archaeoglobus fulgidus [21]. However, to the best of our knowledge, no fungi had yet been isolated from deep geothermal fluids.…”