Thomas A. Langworthy

Thermotoga maritima sp. nov. represents a new genus of unique extremely thermophilic eubacteria growing up to 90°C

A novel type of bacterium has been isolated from various geothermally heated locales on the sea floor. The organisms are strictly anaerobic, rod-shaped, fermentative, extremely thermophilic and grow between 55 and 90°C with an optimum of around 80°C. Cells show a unique sheath-like structure and monotrichous flagellation. By 16S rRNA sequencing they clearly belong to the eubacteria, although no close relationship to any known group could be detected. The majority of their lipids appear to be unique in structure among the eubacteria. Isolate MSB8 is described as Thermotoga maritima, representing the new genus Thermotoga.

Lipids of Archaebacteria

Summary The archaebacteria currently consist of several distinct subgroups including methanogens, extreme halophiles and certain thermoacidophiles. The lipids of archaebacteria are distinguished from those of other prokaryotes and eukaryotes by the absence of fatty acid glycerol ester lipids and the predominance of nonsaponifiable lipids. The lipid composition of the archaebacteria consists of isoprenoid and hydroisoprenoid hydrocarbons and isopranyl glycerol ether lipids. The glycerol ethers of archaebacteria, which constitute the hydrophobic residues of the polar lipids and consequently the membrane interior are diphytanylglycerol diethers or dibiphytanyldiglycerol tetraethers. Either or both glycerol ether structures may be present, depending on genus. The tetraethers of the thermoacidophilic archaebacteria are more specialized in that the dibiphytanyl alkyl chains may contain 1 to 4 cyclopentyl rings. As a consequence of the presence of the tetraethers which can span the membrane, some archaebycterial membranes may exist as a lipid “monolayer” rather than the usual lipid bilayer. The structure of some diether-containing polar lipids of archaebacteria have been well established. The extent of the variety of tetraether containing polar lipid structures is still largely unknown, but both the symmetric and asymmetric substitution of polar head groups to the tetraether has been established in some instances. Among neutral lipids, squalenes and isoprenoid hydrocarbons appear to be universal. The exact pathways for the biosynthesis of the lipid components remain a challenge, but clearly the mevalonate pathway for isoprenoid biosynthesis is the major route of lipid synthesis in archaebacteria rather than the malonyl-CoA pathway for fatty acid biosynthesis in prokaryotes and eukaryotes. The isopranyl glycerol ethers are distinctive, providing a useful taxonomic tool and molecular marker for the identification of archaebacteria. The lipids can also serve as useful biochemical “fossil” evidence for tracing the earlier existence of the organisms. Overall, the discontinuity of archaebacterial lipids formulates a point for delineating early stages of biological evolution and supports the concept that archaebacteria represent a third line of evolutionary descent.

Long-chain diglycerol tetraethers from Thermoplasma acidophilum.

The C40 isopranol-containing glycerol ether residues which characterize the complex lipids of the extreme thermoacidophile Thermoplasma acidophilum were isolated and purified from the glycolipid and phospholipid fractions. The glycerol ether, as well as the acetate and methoxy derivatives were characterized by thin-layer, gel-permeation and gas-liquid chromatography, infrared, nuclear magnetic resonance and mass spectrometry and by vapor phase osmometry. The glycerol ethers are proposed to be unique fully saturated diglycerol tetraethers, primarily C86H172O6, Mr 1300, which contain two sn-2,3-glycerol residues bridged through ether linkages by two C40 isopranoid branched diols.

Squalenes, phytanes and other isoprenoids as major neutral lipids of methanogenic and thermoacidophilic “archaebacteria”

SummaryThe neutral lipids of nine species of methanogenic bacteria including five methanobacilli, two methanococci, a methanospirillum, one methanosarcina as well as two thermoacidophilic bacteria, Thermoplasma and Sulfolobus, were analyzed. The major components were C30, C25 and/or C20 acyclic isoprenoid hydrocarbons with a continuous range of hydroisoprenoid homologues. The range of acyclic isoprenoids detected were from C14 to C30. Apart fromMetbanosarcina barkeri, squalene and/or hydrosqualene derivatives were the predominant components in all species studied. The components ofMetbanosarcina barkeri were a family of C25 homologues. The distribution of the neutral lipid components and their specItIc variations in relative intensities emphasized the differences between the test organisms while the generic nature of the isoprenoid hydrocarbons demonstrated similarities between the diverse bacteria.The neutral lipid compositions from these bacteria, many of which exist in evironmental conditions like those described for the various evolutionary stages of the archean ecology, resemble the isoprenoid distribution isolated from ancient sediments and petroleum. Therefore, these findings may have major implications to biological and biogeochemical evolution.

Staphylothermus marinus sp. nov. Represents a Novel Genus of Extremely Thermophilic Submarine Heterotrophic Archaebacteria Growing up to 98 °C

Summary Two isolates of a new type of extremely thermophilic S 0 -dependent archaebacteria with a GC-content of 35 mol% have been obtained from geothermally heated sediments at the beach of Vulcano, Italy, and from a submarine hydrothermal vent at the East Pacific Rise. The organisms are strictly anaerobic heterotrophic immotile cocci, about 0.5 to 1 μm in diameter, occurring singly, in short chains and, characteristically, in large clusters of up to 100 cells. Giant cells up to 15 μm in diameter are formed at high yeast extract concentrations. Acetate, isovalerate, CO 2 and H 2 S were found as metabolic products. The isolates grow between 1 and 3.5% NaCl and pH 4.5 to 8.5. The optimal growth temperature is 92 or 85 °C, depending upon nutrition. The two isolates are considered to represent a new genus named Staphylothermus with the type species Staphylothermus marinus .

Iso- and Anteiso-Branched Glycerol Diethers of the Thermophilic Anaerobe Thermodesulfotobacterium commune

Thermodesulfotobacterium commune is an extremely thermophilic, anaerobic, sulfate-reducing bacterium that grows optimally at 70 °C and neutral pH. Total lipids comprise about 6.7% of the cell dry weight and consist of 17.1% neutral lipids. 12.6% glycolipids and 70.3% phospholipids. Hydrophobic residues of the glycolipids and phospholipids were released by acid methanolysis and analysed by thin-layer and gas chromatography, infrared and mass spectrometry and by chemical analyses. The hydrophobic residues consisted of sn-l,2-dialkylglycerol diethers (82%), sn-1-alkylglycerol monothers (11%) and fatty acids (7%). Five principal diether species were present containing C(16): C(16), mixed C(16): C(17), C(17): C(17), mixed C(17): C(18), and C(18): C(18) alkyl side chains. The alkyl chains of the diethers and monoethers were comprised of primarily anteiso-C(17) and lesser amounts of iso-C(16), n-C(16), iso-C(17), iso-C(18), n-C(18), anteiso-C(18), iso-C(19) and n-C(l9) hydrocarbons. Among the neutral lipids were identified free fatty acids and a series of C(16) to C(35) hydrocarbons. In contrast to the isopranoid-branched sn-2,3-diphytanylglycerol diethers and dibiphytanyldiglycerol tetraethers that characterize the lipids of thermoacidophilic, halophilic and methanogenic archaebacteria, the diethers of Thermodesulfotobacterium are levorotary (M(D) -16.7°) indicating the sn-1,2-glycerol stereoconfiguration, and they contain O-alkyl chains of variable carbon number (C(16) to C(19)). The presence of glycerol diethers suggests that this organism may have had an evolutionary episode similar to archaebacteria, but the apparent stereochemistry and absence of isopranoid-branched side chains suggests that this organism is perhaps more likely a eubacterium capable of ether lipid biosynthesis. This new class of diethers indicates that a thorough chemical analysis is required when using ether lipids as a chemical marker for the identification of archaebacteria.

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 .

Thermoplasma acidophilum and Thermoplasma volcanium sp. nov. from Solfatara Fields

Summary Twenty-three isolates of motile, cell wall-deficient, thermoacidophilic archaebacteria were obtained from hot acidic springs, soils and sediments within solfatara fields in the Azores, Iceland, Indonesia, Italy, and the United States. They are facultatively anaerobic organotrophs. Anaerobically, the isolates gain energy by sulfur respiration. The new strains resemble Thermoplasma acidophilum by their highly irregular morphology, the lack of a cell envelope and the presence of a serologically homologous histon-like protein. On the basis of their physiological properties, the GC-contents of their DNA and their DNA homology, the new isolates were found to represent (a) Thermoplasma acidophilum, which has only been isolated from self-heated coal refuse piles, and (b) a new species, Thermoplasma volcanium sp. nov., which comprises three different genotypes with insignificant DNA homology with each other and which is described in this paper. Based on the new isolates, an emended description of the genus Thermoplasma and of Thermoplasma acidophilum is given.

A sulfonolipid and novel glucosamidyl glycolipids from the extreme thermoacidophile Bacillus acidocaldarius

The total lipid content of the extreme thermoacidophile Bacillus acidocaldarius comprises about 8.1% of the cell dry weight. Total lipid had a distribution of 15.7% neutral linique component initially characterized as an N-acylglucosamine beta-linked to the primary hydroxyl of an unusual fully saturated pentacyclic triterpene derived tetrol(C35H62O4, Mr 546), which appears to be a derivative of the pentacylcic triterpene hopane substituted at C-29 with a 1,2,3,4-tetrahydroxy pentane. Other major glycolipids present were partially characterized as O-beta-D-glucopyranosyl-(1 leads to 4)-O-2-acylamido-2-deoxy-beta D-glucopyranosyldiacylglycerol and O-beta-D-glucopyranosyl-(1 leads to 4)-O-2-acylamido-2-deoxy-beta-D-glucopyranosylmonoacylglycerol. Minor components of the glycolipid fraction included O-beta-D-glucopyranosyl-(1 leads to 4)-O-2-acylamido-2-deoxy-beta-D-glucopyranosylglycerol, O-2-amino-2-deoxy-beta-D-glucopyranosyl pentacyclic tetrol and free pentacyclic tetrol. The distributions of esterified and amide-linked fatty acids were similar, being comprised primarily of branched heptadecanoic, 11-cyclohexyundecanoic and 13-cyclohexyltridecanoic acids. The acid lipids were composed of a sulfonoglycosyldiacylglycerol (43.2%), diphosphatidylglycerol (32.3%), lysodiphosphatidylglycerol (5.3%), phosphatidic acid (5.8%) and phosphatidylglycerol (13.4%).

Thermosipho africanus gen. nov., Represents a New Genus of Thermophilic Eubacteria within the “Thermotogales”

Summary Three isolates of thermophilic eubacteria were obtained from a marine hydrothermal area at Obock (Djibouti, Africa). The rodshaped cells were surrounded by a sheath-like outer structure, similar to members of the genus Thermotoga . In contrast to Thermotoga , the new bacteria grew in chains (up to twelve rods) surrounded by the sheath. Furthermore, the isolates could be clearly distinguished from Thermotoga by a 11% lower GC-content, an immunologically divergent RNA polymerase, and a much lower growth temperature. 16S rRNA sequencing indicated that the new organisms were related to Thermotoga at the level of a second genus within the “Thermotogales” , which we name Thermosipho . Isolate Ob7 is described as the type species Thermosipho africanus .