Jakob K. Kristjansson

Methanopyrus kandleri, gen. and sp. nov. represents a novel group of hyperthermophilic methanogens, growing at 110°C

A novel group of hyperthermophilic rod-shaped motile methanogens was isolated from a hydrothermally heated deep sea sediment (Guaymas Basin, Gulf of California) and from a shallow marine hydrothermal system (Kolbeinsey ridge, Iceland). The grew between 84 and 110°C (opt: 98°C) and from 0.2% to 4% NaCl (opt. 2%) and pH 5.5 to 7 (opt: 6.5). The isolates were obligate chemolithoautotrophes using H2/CO2 as energy and carbon sources. In the presence of sulfur, H2S was formed and cells tended to lyse. The cell wall consisted of a new type of pseudomurein containing ornithin in addition to lysine and no N-acetylglucosamine. The pseudomurein layer was covered by a detergent-sensitive protein surface layer. The core lipid consisted exclusively of phytanyl diether. The GC content of the DNA was 60 mol%. By 16S rRNA comparisons the new organisms were not related to any of the three methanogenic lineages. Based on the physiological and molecular properties of the new isolates, we describe here a new genus, which we name Methanopyrus (the “methane fire”). The type species is Methanopyrus kandleri (type strain: AV19; DSM 6324).

Influence of Sulfide and Temperature on Species Composition and Community Structure of Hot Spring Microbial Mats

ABSTRACT In solfataric fields in southwestern Iceland, neutral and sulfide-rich hot springs are characterized by thick bacterial mats at 60 to 80°C that are white or yellow from precipitated sulfur (sulfur mats). In low-sulfide hot springs in the same area, grey or pink streamers are formed at 80 to 90°C, and a Chloroflexusmat is formed at 65 to 70°C. We have studied the microbial diversity of one sulfur mat (high-sulfide) hot spring and oneChloroflexus mat (low-sulfide) hot spring by cloning and sequencing of small-subunit rRNA genes obtained by PCR amplification from mat DNA. Using 98% sequence identity as a cutoff value, a total of 14 bacterial operational taxonomic units (OTUs) and 5 archaeal OTUs were detected in the sulfur mat; 18 bacterial OTUs were detected in theChloroflexus mat. Although representatives of novel divisions were found, the majority of the sequences were >95% related to currently known sequences. The molecular diversity analysis showed that Chloroflexus was the dominant mat organism in the low-sulfide spring (1 mg liter−1) below 70°C, whereasAquificales were dominant in the high-sulfide spring (12 mg liter−1) at the same temperature. Comparison of the present data to published data indicated that there is a relationship between mat type and composition of Aquificales on the one hand and temperature and sulfide concentration on the other hand.

Acidianus infernus gen. nov., sp. nov., and Acidianus brierleyi Comb. nov.: Facultatively Aerobic, Extremely Acidophilic Thermophilic Sulfur-Metabolizing Archaebacteria

A new genus, Acidianus, is characterized from studies of 26 isolates of thermoacidophilic archaebacteria from different solfatara fields and marine hydrothermal systems; these isolates grow as facultative aerobes by lithotrophic oxidation and reduction of SO, respectively, and are therefore different from the strictly aerobic Sulfolobus species. The Acidianus isolates have a deoxyribonucleic acid guanine-plus-cytosine content of 31 mol%. In contrast, two of three Sulfolobus species, including the type species, have a guanine-plus-cytosine content of 37 mol%; Sulfolobus brierleyi is the exception, with a guanine-plus-cytosine content of 31 mol%. In contrast to its earlier descriptions, S. brierleyi is able to grow strictly anaerobically by hydrogen-sulfur autotrophy. Therefore, it is described here as a member of the genus Acidianus. The following species are assigned to the genus Acidianus: Acidianus infernus sp. nov. (type strain, strain DSM 3191) and Acidianus brierleyi comb. nov. (type strain, strain DSM 1651).

Rhodothermus marinus, gen. nov., sp. nov., a Thermophilic, Halophilic Bacterium from Submarine Hot Springs in Iceland

SUMMARY: Thermophilic, reddish-coloured heterotrophic bacteria different from Thermus were isolated from submarine alkaline hot springs in Iceland. The bacteria were obligately aerobic, moderately halophilic, Gram-negative rods, about 0.5 μm in diameter and 2-2.5 μm long. Neither spores, flagella nor lipid granules were observed, but a slime capsule was formed on carbohydrate-rich medium. Optimum growth was at 65°C, pH 7.0, and at about 2% (w/v) NaCl. The bacteria were oxidase negative, catalase positive and contained a carotenoid pigment with the main absorbance peak at 476 nm and shoulders at 456 and 502 nm. The GC content of the DNA was about 64 mol%. Electron micrographs clearly showed an outer membrane, about 9 nm thick, and the cytoplasmic membrane together with the peptidoglycan layer was about 14 nm in thickness. The isolates were nutritionally different from Thermus. They utilized several common sugars but glutamate and aspartate were the only amino acids that most strains used. These bacteria are considered to represent a new genus which we name Rhodothermus, with the type species Rhodothermus marinus.

Genetic elements in the extremely thermophilic archaeon Sulfolobus.

Abstract This minireview summarizes what is known about genetic elements in the archaeal crenarchaeotal genus Sulfolobus, including recent work on viruses, cryptic plasmids, a novel type of virus satellite plasmids or satellite viruses, and conjugative plasmids (CPs), mostly from our laboratory. It does not discuss IS elements and transposons.

Methanothermus sociabilis sp. nov., a Second Species within the Methanothermaceae Growing at 97°C

Summary In a survey within continental solfatara fields in Iceland, three new isolates of the Methanothermaceae could be obtained, all thriving within a temperature range between 55 and 97°C with an optimum around 88 °C. One of them grows in large clusters 1 to 3 mm in diameter and turned out to be a new species, which is described as Methanothermus sociabilis .

Pyrobaculum gen. nov., a new genus of neutrophilic, rod-shaped archaebacteria from continental solfataras growing optimally at 100°C

Seven members of a new group of rod-shaped hyperthermophilic neutrophilic archaebacteria were isolated from boiling neutral to alkaline solfataric waters from the Azores, Iceland, and Italy. The organisms are strict anaerobes, growing optimally at 100°C. The cells are motile due to peritrichous or bipolar polytrichous flagellation. The isolates grow facultatively chemolithoautotrophically or obligately heterotrophically. Molecular hydrogen or complex organic substances are used as electron donors. During heterotrophic growth, elemental sulfur, thiosulfate, sulfite, l(-)cystine and oxidized glutathione may serve as electron acceptors depending on the individual strain. Elemental sulfur is strictly required as an electron acceptor for autotrophic growth. The G+C content of the DNA is around 46 mol%. The isolates represent a new genus which we have named Pyrobaculum (the “fire stick”). Two species are described: the facultatively autotrophic Pyrobaculum islandicum (DSM 4184), which is the type species, and the obligately heterotrophic Pyrobaculum organotrophum (DSM 4185).

Phylogenetic diversity analysis of subterranean hot springs in Iceland.

ABSTRACT Geothermal energy has been harnessed and used for domestic heating in Iceland. In wells that are typically drilled to a depth of 1,500 to 2,000 m, the temperature of the source water is 50 to 130°C. The bottoms of the boreholes can therefore be regarded as subterranean hot springs and provide a unique opportunity to study the subterranean biosphere. Large volumes of geothermal fluid from five wells and a mixture of geothermal water from 50 geothermal wells (hot tap water) were sampled and concentrated through a 0.2-μm-pore-size filter. Cells were observed in wells RG-39 (91.4°C) and MG-18 (71.8°C) and in hot tap water (76°C), but no cells were detected in wells SN-4, SN-5 (95 to 117°C), and RV-5 (130°C). Archaea and Bacteria were detected by whole-cell fluorescent in situ hybridization. DNAs were extracted from the biomass, and small-subunit rRNA genes (16S rDNAs) were amplified by PCR using primers specific for the Archaea andBacteria domains. The PCR products were cloned and sequenced. The sequence analysis showed 11 new operational taxonomic units (OTUs) out of 14, 3 of which were affiliated with known surface OTUs. Samples from RG-39 and hot tap water were inoculated into enrichment media and incubated at 65 and 85°C. Growth was observed only in media based on geothermal water. 16S rDNA analysis showed enrichments dominated with Desulfurococcales relatives. Two strains belonging to Desulfurococcus mobilis and to theThermus/Deinococcus group were isolated from borehole RG-39. The results indicate that subsurface volcanic zones are an environment that provides a rich subsurface for novel thermophiles.

The genetic element pSSVx of the extremely thermophilic crenarchaeon Sulfolobus is a hybrid between a plasmid and a virus.

A new Sulfolobus islandicus strain, REY15/4, harboured both a novel fusellovirus, SSV2, and a small plasmid, pSSVx. The plasmid spread in S. solfataricus P1 together with the virus after infection with either the supernatant of a culture of REY15/4 or purified virus. Spreading of the plasmid required co‐transfection with either SSV2 or the related SSV1 as helpers. Virus purified from REY15/4 constituted a mixture of two sizes of particles, one with the dimensions of a normal fusellovirus and the other smaller. Cloned SSV2 produced only the larger particles and only SSV2 DNA, indicating that the smaller particles contained pSSVx packaged into capsids made up of SSV2 components. The 5.7u2003kb genome of pSSVx revealed regions of high sequence similarity to the cryptic Sulfolobales plasmids pRN1, pRN2 and pDL10. Thus, pSSVx belongs to the family of pRN plasmids that share a highly conserved region, which probably constitutes the minimal replicon. They also contain a variable region showing no sequence similarity. In pSSVx, this region contains three open reading frames (ORFs), two of which are juxtapositioned and show high sequence similarity to a tandem of ORFs in fusellovirus genomes. Neither pRN1 nor pRN2, which lack this tandem, spread in the presence of the fuselloviruses, which implies that the sequences of these ORFs enable pSSVx to use the packaging system of the viral helpers for spreading.

Thermophilic organisms as sources of thermostable enzymes

Abstract Thermostable enzymes are receiving considerable attention and there are many industrial applications already. Most thermostable enzymes on the market have, however, been derived from mesophiles. Further research, especially into the possibilities of cloning enzymes from thermophiles into mesophilic hosts, will greatly increase the exploitation of thermophiles in biotechnology.