J. Kuever - Academia.edu (original) (raw)

Papers by J. Kuever

The effect of volcanic activity on submarine hydrothermal systems has been well documented along ... more The effect of volcanic activity on submarine hydrothermal systems has been well documented along fast- and intermediate-spreading centers but not from slow-spreading ridges. Indeed, volcanic eruptions are expected to be rare on slow-spreading axes. Here we report the presence of hydrothermal venting associated with extremely fresh lava flows at an elevated, apparently magmatically robust segment center on the slow-spreading southern Mid-Atlantic Ridge near 5°S. Three high-temperature vent fields have been recognized so far over a strike length of less than 2 km with two fields venting phase-separated, vapor-type fluids. Exit temperatures at one of the fields reach up to 407°C, at conditions of the critical point of seawater, the highest temperatures ever recorded from the seafloor. Fluid and vent field characteristics show a large variability between the vent fields, a variation that is not expected within such a limited area. We conclude from mineralogical investigations of hydrothermal precipitates that vent-fluid compositions have evolved recently from relatively oxidizing to more reducing conditions, a shift that could also be related to renewed magmatic activity in the area. Current high exit temperatures, reducing conditions, low silica contents, and high hydrogen contents in the fluids of two vent sites are consistent with a shallow magmatic source, probably related to a young volcanic eruption event nearby, in which basaltic magma is actively crystallizing. This is the first reported evidence for direct magmatic-hydrothermal interaction on a slow-spreading mid-ocean ridge.

Microbiological Research, 2015

The guts of termites feature suitable conditions for methane oxidizing bacteria (MOB) with their ... more The guts of termites feature suitable conditions for methane oxidizing bacteria (MOB) with their permanent production of CH4 and constant supply of O2via tracheae. In this study, we have isolated MOB from the gut contents of the termites Incisitermes marginipennis, Mastotermes darwiniensis, and Neotermes castaneus for the first time. The existence of MOB was indicated by detecting pmoA, the gene for the particulate methane monooxygenase, in the DNA of gut contents. Fluorescence in situ hybridization and quantitative real-time polymerase chain reaction supported those findings. The MOB cell titer was determined to be 10(2)-10(3) per gut. Analyses of the 16S rDNA from isolates indicated close similarity to the genus Methylocystis. After various physiological tests and fingerprinting methods, no exact match to a known species was obtained, indicating the isolation of new MOB species. However, MALDI-TOF MS analyses revealed a close relationship to Methylocystis bryophila and Methylocystis parvus.

Systematic and Applied Microbiology, 1995

The phylogenetic relationships of three ThlOploca species, T. arat/we, T. chile,le and T. ingrica... more The phylogenetic relationships of three ThlOploca species, T. arat/we, T. chile,le and T. ingrica. as well as Beggiatoa alba, Beggiatoa sp. str 1401-13, and Thiothrix nh'ea were determined by 165 rRNA sequence analysis. Fluorescent in situ hybridization with Thioploca-specific oligonucleotide probes was used to substantiate the sequences of T. arat/cae and T. chileae. All three Thioploca species form a monophyletic group. They are affiliated with Beggiatoa alba and Beggiatoa sp. 5tr 1401-13. Thioploca and Beggiatoa constitute a new phylogenetic lineage within the gamma-subdivision of the proteobacteria, showing similar genetic diversity as other major groups of gamma-or beta-subdivision sulfur oxidizers. Thiothrix nivea is a member of the gamma proteobacteria, but does not form a monophyletic lineage with Beggiatoa and Thioploca.

International Journal of Systematic and Evolutionary Microbiology, 2005

Two psychrophilic, chemolithoautotrophic, sulfur-oxidizing bacteria were isolated from marine Arc... more Two psychrophilic, chemolithoautotrophic, sulfur-oxidizing bacteria were isolated from marine Arctic sediments sampled off the coast of Svalbard with thiosulfate as the electron donor and CO2 as carbon source. Comparative analysis of 16S rRNA gene sequences suggested that the novel strains, designated SVAL-DT and SVAL-ET, represent members of the genus Thiomicrospira. Further genotypic (DNA–DNA relatedness, DNA G+C content) and phenotypic characterization revealed that the strains represent members of two novel species. Both organisms are obligately autotrophic and strictly aerobic. Nitrate was not used as an electron acceptor. Chemolithoautotrophic growth was observed with thiosulfate, tetrathionate and sulfur. The temperature limits for growth of both strains were between −2 °C and 20·8 °C, with optima of 11·5–13·2 °C (SVAL-ET) and 14·6–15·4 °C (SVAL-DT), which is about 13–15 °C lower than the optima of all other recognized Thiomicrospira species. The maximum growth rate on thiosu...

European Journal of Phycology, 1998

... WOLFGANG GROSS1, JAN KU=VER2, GILBERT TISCHENDORF1, NICOLAS BOUCHAALA3 AND WILHELM BU=SCH4 ..... more ... WOLFGANG GROSS1, JAN KU=VER2, GILBERT TISCHENDORF1, NICOLAS BOUCHAALA3 AND WILHELM BU=SCH4 ... Cells were grown heterotrophically on 50 mM galactose (Galdieria sulphuraria strain 002P and strain 074: Pinto et al., 1992) or autotrophically (Cyanidium ...

Archives of Microbiology, 1995

Cyclohexane carboxylate supported relatively rapid growth (doubling times 7-8 h) of Rhodopseudomo... more Cyclohexane carboxylate supported relatively rapid growth (doubling times 7-8 h) of Rhodopseudomonas palustris under oxic or photosynthetic conditions, but did not serve as a substrate for either of the known aromatic CoA ligases. A CoA ligase that thioesterifies cyclohexane carboxylate was partially purified and did not cross react immunologically with the two CoA ligases purified previously from this bacterium. Crude extracts of R. palustris cells grown with a range of aromatic or alicyclic acids contained a dehydrogenase that reacted with cyclohexane carboxyl-CoA or cyclohex-1-ene carboxyl-CoA, using 2,6-dichlorophenolindophenol or ferricenium ion as electron carrier. This activity was not detected in extracts of adipate-, glutamate-, or succinate-grown cells. No oxidation or reduction of nonesterified cyclohexane carboxylate or cyclohexene carbocylate was detected in extracts of cells grown with aromatic or aliphatic substrates, neither aerobically nor anaerobically. A constitutively expressed thioesterase that hydrolyzed cyclohexane carboxyl-CoA and also some alicyclic and aliphatic CoA derivatives was purified and characterized. The enzyme had little or no activity on benzoyl-CoA or 4-hydroxybenzoyl-CoA. The presence of a thioesterase that effectively hydrolyzes cyclohexane carboxyl-CoA suggests that transient production of cyclohexane carboxylate is a physiological response to temporary excess of reductant during metabolism of aromatic compounds.

Archives of Microbiology, 1993

A new sulfate-reducer "strain SAX" was isolated from an anaerobic marine sedime... more A new sulfate-reducer "strain SAX" was isolated from an anaerobic marine sediment [Saxild, Denmark]. The isolate was a gram-negative, motile and non-spore-forming rod which sometimes appeared as a curved rod. Strain SAX differed from all described Desulfovibrio-, Desulfobotulus- and Desulfoarculus-species by the ability to degrade aromatic compounds such as benzoate, 4-hydroxybenzoate and phenol completely to CO2. Electron donors used included lactate, pyruvate, malate, fumarate, crotonate and butyrate, while pyruvate was fermented in the absence of an external electron acceptor. Sulfate, thiosulfate or sulfite served as electron acceptors with benzoate as the donor, while nitrate and nitrite did not. The sulfate-reducing bacterium required vitamins and NaCl-concentrations of about 20 g/l. The optimum temperature for growth of strain SAX was 30 degrees C and the optimum pH value was 7.3. The DNA base composition was 62.4 mol% G+C. The strain possessed cytochrome c3, but no desulfoviridin. On the basis of these characteristics and because strain SAX could not be ascribed to any of the existing species therefore assignment as a new species to the genus Desulfoarculus was suggested.

Journal of General Microbiology, 1993

The transformation of several mono-and dinitroaromatic compounds (tested at 50-200 p~) by methano... more The transformation of several mono-and dinitroaromatic compounds (tested at 50-200 p~) by methanogenic bacteria, sulphate-reducing bacteria and clostridia was studied. Some of the nitroaromatics tested were transformed chemically by 1.5 mM quantities of culture media reducing agents, like cysteine or sulphide. This abiotic reduction occurred at the o-nitro-groups preferentially. Nitrophenols, p-nitroaniline and p-nitrobenzoic acid were completely transformed biologically into the corresponding amino derivatives. The nitroaromatics were transformed by all of the bacterial strains tested. While growing cells of sulphate-reducing bacteria and Clostridium spp. carried out nitroreduction, methanogen cells lysed in the presence of nitroaromatics. Nevertheless these culture suspensions converted nitroaromatics to the corresponding amino derivatives. This was also confirmed by crude cell extracts of methanogenic bacteria. The rate of nitroreduction by sulphate-reducing bacteria depended on the electron donors supplied and the cell density, with molecular hydrogen being the most effective donor of reducing equivalents. The toxicity of p-nitrophenol to some of the organisms tested depended on the concentration of the nitroaromatic compound and the type of organism.

Heritage Microbiology and Science, 2008

... Citation: The BIOBRUSH project for bioremediation of heritage stone / E. May, AM Webster, R. ... more ... Citation: The BIOBRUSH project for bioremediation of heritage stone / E. May, AM Webster, R. Inkpen, D. Zamarreño, J. Kuever, C. Rudolph, T. Warscheid, C. Sorlini, F. Cappitelli, E. Zanardini, G. Ranalli, L. Krage, A. Vgenopoulos, D. Katsinis, E. Mello, M. Malagodi - In: Heritage ...

Journal of Bacteriology, 2005

The dissimilatory reduction of sulfate is an ancient metabolic process central to today's bio... more The dissimilatory reduction of sulfate is an ancient metabolic process central to today's biogeochemical cycling of sulfur and carbon in marine sediments. Until now its polyphyletic distribution was most parsimoniously explained by multiple horizontal transfers of single genes rather than by a not-yet-identified “metabolic island.” Here we provide evidence that the horizontal transfer of a gene cluster may indeed be responsible for the patchy distribution of sulfate-reducing prokaryotes (SRP) in the phylogenetic tree. We isolated three DNA fragments (32 to 41 kb) from uncultured, closely related SRP from DNA directly extracted from two distinct marine sediments. Fosmid ws39f7, and partially also fosmids ws7f8 and hr42c9, harbored a core set of essential genes for the dissimilatory reduction of sulfate, including enzymes for the reduction of sulfur intermediates and synthesis of the prosthetic group of the dissimilatory sulfite reductase. Genome comparisons suggest that encoded m...

Environmental Microbiology, 2007

Applied and Environmental Microbiology, 2006

Gutless oligochaetes are small marine worms that live in obligate associations with bacterial end... more Gutless oligochaetes are small marine worms that live in obligate associations with bacterial endosymbionts. While symbionts from several host species belonging to the genus Olavius have been described, little is known of the symbionts from the host genus Inanidrilus. In this study, the diversity of bacterial endosymbionts in Inanidrilus leukodermatus from Bermuda and Inanidrilus makropetalos from the Bahamas was investigated using comparative sequence analysis of the 16S rRNA gene and fluorescence in situ hybridization. As in all other gutless oligochaetes examined to date, I. leukodermatus and I. makropetalos harbor large, oval bacteria identified as Gamma 1 symbionts. The presence of genes coding for ribulose-1,5-bisphosphate carboxylase/oxygenase form I (cbbL) and adenosine 5′-phosphosulfate reductase (aprA) supports earlier studies indicating that these symbionts are chemoautotrophic sulfur oxidizers. Alphaproteobacteria, previously identified only in the gutless oligochaete Ol...

Soil fungal communities are important for soil ecosystem functioning. In particular, they are the... more Soil fungal communities are important for soil ecosystem functioning. In particular, they are the most important group of organisms involved in decomposing organic matter, especially for resistant compounds such as lignin. Therefore, fungi have an important impact on the decomposition of straw in soil. In paddy soils, fungal communities are predominant only after drainage and during post-harvest fallow conditions as they need oxygen which is limited under flooded conditions. To investigate the influence of soil management practices on fungi in paddy soils, the period of drainage after flooding was simulated in soil microcosms. In addition, different rice straw applications were tested in an incubation experiment. Molecular analysis including DNA-extraction and PCR/DGGE-analysis was used to characterize the soil fungal communities in these experiments. The resulting dendrograms show clear shifts and correlations between the simulated water stages and rice straw applications.

Bergey’s Manual® of Systematic Bacteriology, 2005

Revista de biología tropical, 1996

Our basic microbiological studies of the water column and the sediment of Golfo Dulce, Costa Rica... more Our basic microbiological studies of the water column and the sediment of Golfo Dulce, Costa Rica, were focused on aerobic and denitrifying sulfur-oxidizing bacteria and anaerobic sulfate-reducing bacteria. We observed no increasing numbers of total bacterial counts within the water column. Although no oxygen was present hydrogen sulfide was only detectable close to the sediment. The highest numbers of sulfate-reducing bacteria measured by Most-Probable-Number counts were found in or close to the sediment. In the anoxic bottom water sulfide-oxidizing bacteria typically containing large sulfur globules were observed microscopically. They were identified as free-swimming Thiovulum and Thiospira species. At one station large vacuolated forms of the filamentous colourless sulfur bacterium Beggiatoa were noted. Together with these sulfur containing bacteria there were long free swimming rods showing no sulfur inclusions of unknown character. The microscopic observations showed good corre...