title: Survival of Desulfotomaculum spores from estuarine sediments after serial autoclaving and high-temperature exposure.
abstract: Bacterial spores are widespread in marine sediments, including those of thermophilic, sulphate-reducing bacteria, which have a high minimum growth temperature making it unlikely that they grow in situ. These Desulfotomaculum spp. are thought to be from hot environments and are distributed by ocean currents. Their cells and spores upper temperature limit for survival is unknown, as is whether they can survive repeated high-temperature exposure that might occur in hydrothermal systems. This was investigated by incubating estuarine sediments significantly above (40-80 °C) maximum in situ temperatures (∼ 23 °C), and with and without prior triple autoclaving. Sulphate reduction occurred at 40-60 °C and at 60 °C was unaffected by autoclaving. Desulfotomaculum sp. C1A60 was isolated and was most closely related to the thermophilic D. kuznetsovii(T) (∼ 96% 16S rRNA gene sequence identity). Cultures of Desulfotomaculum sp. C1A60, D. kuznetsovii(T)and D. geothermicum B2T survived triple autoclaving while other related Desulfotomaculum spp. did not, although they did survive pasteurisation. Desulfotomaculum sp. C1A60 and D. kuznetsovii cultures also survived more extreme autoclaving (C1A60, 130 °C for 15 min; D. kuznetsovii, 135 °C for 15 min, maximum of 154 °C reached) and high-temperature conditions in an oil bath (C1A60, 130° for 30 min, D. kuznetsovii 140 °C for 15 min). Desulfotomaculum sp. C1A60 with either spores or predominantly vegetative cells demonstrated that surviving triple autoclaving was due to spores. Spores also had very high culturability compared with vegetative cells (∼ 30 × higher). Combined extreme temperature survival and high culturability of some thermophilic Desulfotomaculum spp. make them very effective colonisers of hot environments, which is consistent with their presence in subsurface geothermal waters and petroleum reservoirs.
authors.affiliation: School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, Wales, UK.
authors.forename: Louise A
authors.initials: LA
authors.lastname: O'Sullivan
authors.affiliation: School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, Wales, UK.
authors.forename: Erwan G
authors.initials: EG
authors.lastname: Roussel
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3AT, Wales, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Weightman
authors.affiliation: 1] School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, Wales, UK [2] Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3AT, Wales, UK.
authors.forename: Gordon
authors.initials: G
authors.lastname: Webster
authors.affiliation: School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Casey R J
authors.initials: CR
authors.lastname: Hubert
authors.affiliation: School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Emma
authors.initials: E
authors.lastname: Bell
authors.affiliation: School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Head
authors.affiliation: School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, Wales, UK.
authors.forename: Henrik
authors.initials: H
authors.lastname: Sass
authors.affiliation: School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, Wales, UK.
authors.forename: R John
authors.initials: RJ
authors.lastname: Parkes
mesh_terms: D045859:Desulfotomaculum / Q000145:classification / Q000502:physiology*; D063366:Estuaries; D019015:Geologic Sediments / Q000382:microbiology*; D006358:Hot Temperature; D050296:Microbial Viability; D010084:Oxidation-Reduction; D010802:Phylogeny; D013171:Spores, Bacterial / Q000502:physiology