Terje Torsvik

Microbes play an important role in the alteration of oceanic crust

Microbes have been identified within altered parts of the glass rims of pillow lavas in the upper oceanic crust, 237 m below the top of the volcanic basement of ODP Hole 896A at the Costa Rica Rift. Their presence is verified by spherical and vermicular microbodies containing DNA. The elemental composition of the microbially processed areas differ from the parent glass. Further, the microbially processed parts, showing different morphological forms also show different elemental composition. Extreme K-enrichment indicate that microbes are presently active in the alteration process. The carbon isotopic composition of disseminated carbonates within the basaltic section of the Hole 504B (1 km distance from Hole 896A) also give evidence for microbial activity during rock alteration. The σ13C values of most of these trace carbonates are very low, reflecting metabolic control of the carbon cycle in these rocks. Microbial alteration of basaltic glass, comprising a substantial volume and surface area of the upper oceanic crust, may thus play an important role in the element exchange between oceanic crust and seawater.

Evidence for microbial activity at the glass-alteration interface in oceanic basalts

A detailed microbiological and geochemical study related to the alteration of basaltic glass of pillow lavas from the oceanic crust recovered from Hole 896A on the Costa Rica Rift (penetrating 290 m into the volcanic basement) has been carried out. A number of independent observations, pointing to the influence of microbes, may be summarized as follows: (1) Alteration textures are reminiscent of microbes in terms of form and shape. (2) Altered material contains appreciable amounts of C, N and K, and the N=C ratios are comparable to those of nitrogen-starved bacteria. (3) Samples stained with a dye (DAPI) that binds specifically to nucleic acids show the presence of DNA in the altered glass. Further, staining with fluorescent labeled oligonucleotide probes that hybridize specifically to 16S-ribosomal RNA of bacteria and archaea demonstrate their presence in the altered part of the glass. (4) Disseminated carbonate in the glassy margin of the majority of pillows shows d 13 C values, significantly lower than that of fresh basalt, also suggests biological activity. The majority of the samples have d 18 O values indicating temperatures of 20‐100oC, which is in the range of mesophilic and thermophilic micro-organisms.

Diversity of life in ocean floor basalt

Abstract Electron microscopy and biomolecular methods have been used to describe and identify microbial communities inhabiting the glassy margins of ocean floor basalts. The investigated samples were collected from a neovolcanic ridge and from older, sediment-covered lava flows in the rift valley of the Knipovich Ridge at a water depth around 3500 m and an ambient seawater temperature of −0.7°C. Successive stages from incipient microbial colonisation, to well-developed biofilms occur on fracture surfaces in the glassy margins. Observed microbial morphologies are various filamentous, coccoidal, oval, rod-shaped and stalked forms. Etch marks in the fresh glass, with form and size resembling the attached microbes, are common. Precipitation of alteration products around microbes has developed hollow subspherical and filamentous structures. These precipitates are often enriched in Fe and Mn. The presence of branching and twisted stalks that resemble those of the iron-oxidising Gallionella , indicate that reduced iron may be utilised in an energy metabolic process. Analysis of 16S-rRNA gene sequences from microbes present in the rock samples, show that the bacterial population inhabiting these samples cluster within the γ- and ϵ-Proteobacteria and the Cytophaga/Flexibacter/Bacteroides subdivision of the Bacteria, while the Archaea all belong to the Crenarchaeota kingdom. This microbial population appears to be characteristic for the rock and their closest relatives have previously been reported from cold marine waters in the Arctic and Antarctic, deep-sea sediments and hydrothermal environments.

Microbial community diversity in seafloor basalt from the Arctic spreading ridges

Microbial communities inhabiting recent (< or =1 million years old; Ma) seafloor basalts from the Arctic spreading ridges were analyzed using traditional enrichment culturing methods in combination with culture-independent molecular phylogenetic techniques. Fragments of 16S rDNA were amplified from the basalt samples by polymerase chain reaction, and fingerprints of the bacterial and archaeal communities were generated using denaturing gradient gel electrophoresis. This analysis indicates a substantial degree of complexity in the samples studied, showing 20-40 dominating bands per profile for the bacterial assemblages. For the archaeal assemblages, a much lower number of bands (6-12) were detected. The phylogenetic affiliations of the predominant electrophoretic bands were inferred by performing a comparative 16S rRNA gene sequence analysis. Sequences obtained from basalts affiliated with eight main phylogenetic groups of Bacteria, but were limited to only one group of the Archaea. The most frequently retrieved bacterial sequences affiliated with the gamma-proteobacteria, alpha-proteobacteria, Chloroflexi, Firmicutes, and Actinobacteria. The archaeal sequences were restricted to the marine Group 1: Crenarchaeota. Our results indicate that the basalt harbors a distinctive microbial community, as the majority of the sequences differed from those retrieved from the surrounding seawater as well as from sequences previously reported from seawater and deep-sea sediments. Most of the sequences did not match precisely any sequences in the database, indicating that the indigenous Arctic ridge basalt microbial community is yet uncharacterized. Results from enrichment cultures showed that autolithotrophic methanogens and iron reducing bacteria were present in the seafloor basalts. We suggest that microbial catalyzed cycling of iron may be important in low-temperature alteration of ocean crust basalt. The phylogenetic and physiological diversity of the seafloor basalt microorganisms differed from those previously reported from deep-sea hydrothermal systems.

Desulfotomaculum thermocisternum sp. nov., a Sulfate Reducer Isolated from a Hot North Sea Oil Reservoir

The organism described in this paper, strain ST90T (T = type strain), is a thermophilic, spore-forming, rod-shaped sulfate reducer that was isolated from North Sea oil reservoir formation water. In cultivation the following substances were used as electron donors and carbon sources: H2-CO2, lactate, pyruvate, ethanol, propanol, butanol, and C3 to C10 and C14 to C17 carboxylic acids. Sulfate was used as the electron acceptor in these reactions. Lactate was incompletely oxidized. Sulfite and thiosulfate were also used as electron acceptors. In the absence of an electron acceptor, the organism grew syntrophically on propionate together with a hydrogenothrophic methanogen. The optimum conditions for growth on lactate and sulfate were 62°C, pH 6.7, and 50 to 200 mM NaCI. The G+C content was 56 mol%, as determined by high-performance liquid chromatography and 57 mol% as determined by thermal denaturation. Spore formation was observed when the organism was grown on butyrate or propanol as a substrate and at low pH values. On the basis of differences in G+C content and phenotypic and immunological characteristics when the organism was compared with other thermophilic Desulfotomaculum species, we propose that strain ST90T is a member of a new species, Desulfotomaculum thermocisternum. D. thermocisternum can be quickly identified and distinguished from closely related Desulfotomaculum species by immunoblotting.

Thermodesulforhabdus norvegicus gen. nov., sp. nov., a novel thermophilic sulfate-reducing bacterium from oil field water

A novel gram-negative, thermophilic, acetate-oxidizing, sulfate-reducing bacterium, strain A8444, isolated from hot North Sea oil field water, is described. The rod-shaped cells averaged 1 μm in width and 2.5 μm in length. They were motile by means of a single polar flagellum. Growth was observed between 44 and 74°C, with an optimum at 60°C. Spores were not produced. Sulfate and sulfite were used as electron acceptors. Sulfur, thiosulfate, nitrate, fumarate, and pyruvate were not reduced. In the presence of sulfate, growth was observed with acetate, lactate, pyruvate, butyrate, succinate, malate, fumarate, valerate, caproate, hepatanoate, octanoate, nonadecanoate, decanoate, tridecanoate, pentadecanoate, palmitate, heptadecanoate, stearate, and ethanol. Pyruvate, lactate, and fumarate did not support fermentative growth. Cytochromes of thec-type were present. Desulfoviridin, desulforubidin, P582, and desulfofuscidin were not present. The G+C content of the DNA was 51 mol%. Sequence analysis of 16S rDNA showed that phylogenetically strain A8444 belongs to the delta subdivision of the Proteobacteria. The closest relatives areDesulfacinum infernum andSyntrophobacter wolinii. Strain A8444 is described as the type strain of the new taxonThermodesulforhabdus norvegicus gen. nov., sp. nov.

Microbial fractionation of carbon isotopes in altered basaltic glass from the Atlantic Ocean, Lau Basin and Costa Rica Rift

Abstract Textural and DNA studies of pillow lavas in DSDP/ODP cores from the Atlantic Ocean, the Lau Basin and the Costa Rica Rift indicate that microbes had a significant role in the alteration of basaltic glasses. Carbon isotopes ( δ 13 C) in carbonates from glassy and crystalline basalts from these locations also show differences that may relate to microbial activity during alteration. The generally low δ 13 C values ( Bacteria and oxidation of organic matter. Positive δ 13 C values of some samples from the Atlantic suggest lithotrophic utilization of CO 2 , in which methanogenic Archaea produced CH 4 from H 2 and CO 2 . This may result from higher abiotic production of H 2 in the slow-spreading, fault-dominated Atlantic crust, due to more extensive serpentinization than at the intermediate-spreading Costa Rica Rift.

Persisting Phage Infection in Halobacterium salinarium str. 1

Summary Cultures of Halobacterium salinarium str. 1 are persistently infected with the virulent and extremely halophilic phage Hs1. The nature of phage infection depended on the salt concentration in the medium, changing from lytic to persistent as the salt concentration increased from 17.5 to 30% (w/v) NaCl. At salt concentrations below 25% (w/v) NaCl, phage infection resulted in a lytic development with phage production. The lytic development was characterized by a constant eclipse and latent period, irrespective of bacterial growth rate or salt concentration. At salt concentrations above 25% (w/v) NaCl phage infection resulted in the establishment of a carrier state in which lysis of the infected bacteria was delayed for several generations. In this carrier state the infected bacteria continued to multiply at the same rate as uninfected cells. Bacteria infected under conditions favouring lytic development could survive if transferred to a medium which favoured the formation of carrier cells. More than 77% of the bacteria infected with phage in a medium containing 20% (w/v) NaCl were able to form colonies if plated 90 min p.i. on agar plates containing 30% (w/v) NaCl. A majority of the colonies carried phage.

Biogenic alteration of volcanic glass from the Troodos ophiolite, Cyprus

Alteration of basaltic glass through the entire volcanic sequence of the Troodos ophiolite is partly bio-mediated. The following observations support this conclusion: alteration textures resembling microbes in form and size; altered glass locally shows high carbon concentrations at the alteration front and organic remains. The absence of DNA suggests that the bio-alteration is a fossil process. Temperatures calculated from δ18O of carbonate, assumed to have been in equilibrium with seawater, yield 27–65°C, and δ18Osilicate versus H2O relationships indicate seawater alteration. These data are consistent with biogenic alteration during an early stage of ocean-floor alteration of the Troodos oceanic crust some 70–90 Ma ago.

The tectonic implications of Solundian (Upper Devonian) magnetization of the Devonian rocks of Kvamshesten, western Norway

The allochthonous Old Red Sandstone of Kvamshesten, western Norway, records polyphase orogenic deformation, and palaeomagnetic results from both the Devonian sediments and mylonites associated with the basal thrust define a syn- (to post-) tectonic magnetization withD = 218°,I = +3° andα95 = 9.7°. The corresponding pole position (lat. 21°S, long. 324°E) suggests a Late Devonian/Early Carboniferous magnetization age (Solundian), and probably dates the time of thrust movements.