Barbara Nicolaus

Archaeoglobus profundus sp. nov., Represents a New Species within the Sulfate-reducing Archaebacteria

Summary Eleven isolates of nonmotile coccoid hyperthermophilic archaebacteria growing at temperatures up to 90 °C were obtained from the walls of active smokers and from sediments from a deep sea hydrothermal system at Guaymas, Mexico. Similar to Archaeoglobus fulgidus, they were sulfidogens showing a blue-green fluorescence at 420 nm. Sulfate, thiosulfate and sulfite served as electron acceptors. Elemental sulfur inhibited growth. In contrast to A. fulgidus, the new isolates were obligate mixotrophs strictly requiring H2 and an organic carbon source (e. g. acetate). One of the new isolates was studied in more detail. It could be further distinguished from A. fulgidus by a 5 mol% lower GC-content of its DNA (41 mol%), a different pattern of complex lipids, and by insignificant DNA homology. On the basis of these distinguishing features, a new species, Archaeoglobus profundus is described in this paper. Type strain is A. profundus AV 18 (DSM5631).

Effects of temperature on ether lipid composition of Caldariella acidophila

The composition of the ether lipids of a strain of Caldariella acidophila, with respect to the different numbers of cyclizations of the biphytanyl components, is shown to differ between the various complex lipid classes, but the degree of cyclization increases systematically with the growth temperature in the range 75–89°. The problem of distinguishing adaptive from phyletic features in archaebacterial lipids is considered.

Isoprenoid ethers; backbone of complex lipids of the archaebacterium Sulfolobus solfataricus

Abstract The complex lipids of Sulfolobus solfataricus (previously named Caldariella acidophila ), a thermophilic archaebacterium, are based on 72-membered macrocyclic tetraethers made up from two C 40 diol units and either two glycerol units or one glycerol and a unique branched-chain nonitol, named calditol. The C 40 components have the 16,16-biphytanyl skeleton with up to four cyclopentane rings. Individual isoprenoid ethers, backbone of complex lipids, are separated by high-performance liquid chromatography (HPLC) and the structures of 20 different species are fully described. The structures allow previous observations on these and related lipids to be rationalized biosynthetically.

Chemical composition and production of exopolysaccharides from representative members of heterocystous and non-heterocystous cyanobacteria

Exopolysaccharide (EPS) production and chemical composition of heterocystous and non-heterocystous cyanobacteria of subgroups 3, 4, and 5 together with four new species isolated from Pantelleria (Italy) hard sands and from a lake in the proximity of Edmonson Point in Antarctica were studied. The yield of extracellular soluble polysaccharides (RPS) and slime layers (CPS) showed a significant variation from one strain to another; generally RPS were more abundant than CPS with the exception of Anabaena torulosa and Scytonema hoffmanni. Phormidium sp. was the best producer of EPS. Among heterocystous cyanobacteria belonging to Nostocaceae the new species Anabaena WSAF and A. torulosa were found to produce the highest level of EPS. Among heterocystous cyanobacteria other than Nostocaceae, the best producer of EPS was Chlorogloeopsis sp. 6912. Four species were chosen for studying the effects of growth conditions, nutritional, physical and chemical, on total EPS formed. Glucose and galactose were the neutral sugars widely present in the species examined, although other sugars such as mannose and xylose were plentiful in some species. Amino-sugar, as glucosamine, and uronic acids were also found in EPS of some cyanobacteria. Finally the inhibition of avarol, a sesquiterpene hydroquinone, toxicity on Artemia salina by EPS of some species was analysed.

Characterization of a Haloalkalophilic Strictly Aerobic Bacterium, Isolated from Pantelleria Island

Summary The morphological, physiological and genetic characteristics of an isolate (AAP) from hard sand of the lake of Venere in the Pantelleria island (Italy) were described. The isolate, growing optimally at pH 9.0 in the presence of 10% of NaCl at 33–35°C, was a Gram-negative pleomorphic rod, strictly aerobic, capable of accumulating polyhydroxybutyrate. The isolate was able to grow on different carbon sources in presence of thiamine or biotin. The G+C content of DNA was 65.02% and its phylogenetic position was elucidated by 16S rRNA cataloguing. The isolate AAP clustered phylogenetically within the gamma subclass of the Proteobacteria and is closely related to the other species on the Halomonas-Deleya branch. The haloalkalophilic strain should be placed in a new species of the genus Halomonas for which the name “Halomonas pantelleriense” is proposed.

Unique Features of Lipids of Archaea

Summary Lipid composition has proved particularly useful in the taxonomy of microorganisms. The most spectacular grouping that can be made among prokaryotes, on the basis of lipid analysis, is the Archaea whose membranes are based on isopranoid glycerol ether lipids. This presentation is meant to give an updated general survey of the structural features of lipids of Archaea and the significance of lipid composition in archaeal taxonomy.

An Asymmetric Archaebacterial Diether Lipid from Alkaliphilic Halop hile s

SUMMARY: Archaebacterial halophiles from alkaline soda lakes were shown to possess substantial amounts of a core diether lipid differing from the C20,C20 diether lipid characteristic of Halococcus and Halobacterium spp. This novel diether lipid was shown to be an asymmetric C20,C25 diether (2-O-sesterterpanyl-3-0-phytanyl-sn-glycerol). The implications of this unusual lipid for membrane structure are discussed.

Complex lipids of Caldariella acidophila, a thermoacidophile archaebacterium

Abstract Isoprenoid ether lipids are common to the ‘urkingdom’ archaebacteria, within which members of the Caldariella group of extreme thermoacidophiles and some methanogenic species have lipids based on macrocyclic tetraethers containing two 16,16′-biphytanyl chains. As a step towards closer classification, the complex lipids of Caldariella acidophila have been more fully characterized.

“Bacillus thermoantarcticus” sp. nov., from Mount Melbourne, Antarctica: a novel thermophilic species

Abstractu2002A novel thermophilic Gram-positive bacillus, “Bacillus thermoantarcticus”, isolated from geothermal soil near the crater of Mount Melbourne, is described. The organism grows at an optimal temperature of 63°C at pH 6.0, is oxidase-positive, catalase-negative and produces an exopolysaccharide, an exocellular xylanase, an intracellular alcohol dehydrogenase and exo- and endocellular α-glucosidase(s). The sequence of 16S rDNA is very similar to that of “Bacillus thermoglucosidasius”; however, the guanine-plus-cytosine (G+C) content is 8u2005mol% higher. The type strain is “Bacillus thermoantarcticus” (DSM 9572).

A C25,C25 Diether Core Lipid from Archaebacterial Haloalkaliphiles

SUMMARY: The membrane lipids from an archaebacterial haloalkaliphile were shown to be based almost entirely on diethers containing C25 isopranyl chains. The ‘universal’ C20,C20 archaebacterial diether core lipid (2,3-di-O-phytanyl-sn-glycerol) made up only 9% (w/w) of the total isopranoid diether fraction. The rest of the isopranoid diether fraction comprised 85% (w/w) C20,C25 diether (2-O-sesterterpanyl-3-O-phytanyl-sn-glycerol) and 6% (w/w) of a novel C25,C25 diether (2,3-di-O-sesterterpanyl-sn-glycerol).