Lipoquinones of some bacteria and mycoplasmas, with considerations on their functional significance

Multiple Rieske/cytb complexes in a single organism

Most organisms contain a single Rieske/cytb complex. This enzyme can be integrated in any respiratory or photosynthetic electron transfer chain that is quinone-based and sufficiently energy rich to allow for the turnover of three enzymes - a quinol reductase, a Rieske/cytb complex and a terminal oxidase. Despite this universal usability of the enzyme a variety of phylogenetically distant organisms have multiple copies thereof and no reason for this redundancy is obvious. In this review we present an overview of the distribution of multiple copies among species and describe their properties from the scarce experimental results, analysis of their amino acid sequences and genomic context. We discuss the predicted redox properties of the Rieske cluster in relation to the nature of the pool quinone. It appears that acidophilic iron-oxidizing bacteria specialized one of their two copies for reverse electron transfer, archaeal Thermoprotei adapted their three copies to the interaction with different oxidases and several, phylogenetically unrelated species imported a second complex with a putative heme ci that may confer some yet to be determined properties to the complex. These hypothesis and all the more the so far completely unexplained cases call for further studies and we put forward a number of suggestions for future research that we hope to be stimulating for the field. This article is part of a Special Issue entitled: Respiratory complex III and related bc complexes.

A new lineage of halophilic, wall-less, contractile bacteria from a brine-filled deep of the Red Sea

A novel strictly anaerobic bacterium designated strain SSD-17B(T) was isolated from the hypersaline brine-sediment interface of the Shaban Deep, Red Sea. Cells were pleomorphic but usually consisted of a central coccoid body with one or two "tentacle-like" protrusions. These protrusions actively alternated between a straight, relaxed form and a contracted, corkscrew-like one. A peptidoglycan layer was not detected by electron microscopy. The organism forms "fried-egg"-like colonies on MM-X medium. The organism is strictly anaerobic and halophilic and has an optimum temperature for growth of about 30 to 37 degrees C and an optimum pH of about 7. Nitrate and nitrite are reduced; lactate is a fermentation product. The fatty acid profile is dominated by straight saturated and unsaturated chain compounds. Menaquinone 4 is the major respiratory quinone. Phylogenetic analysis demonstrated strain SSD-17B(T) represents a novel and distinct lineage within the radiation of the domain Bacteria. The branching position of strain SSD-17B(T) was equidistant to the taxa considered to be representative lineages of the phyla Firmicutes and Tenericutes (with its sole class Mollicutes). The phenotypic and phylogenetic data clearly show the distinctiveness of this unusual bacterium, and we therefore propose that strain SSD-17B(T) (= DSM 18853 = JCM 14575) represents a new genus and a new species, for which we recommend the name Haloplasma contractile gen. nov., sp. nov. We are also of the opinion that the organism represents a new order-level taxon, for which we propose the name Haloplasmatales.

Flash detection/identification of pathogens, bacterial spores and bioterrorism agent biomarkers from clinical and environmental matrices

We propose to develop an integrated rapid, semiportable, prototype point microbial detection/identification system for clinical specimens that is also capable of differentiating microbial bioterrorism attacks from threats or hoaxes by defining the pathogen. The system utilizes "flash" extraction/analytical system capable of detection/identification of microbes from environmental and clinical matrices. The system couples demonstrated technologies to provide quantitative analysis of lipid biomarkers of microbes including spores in a system with near-single cell (amol/microl) sensitivity. Tandem mass spectrometry increases specificity by providing the molecular structure of neutral lipids, phospholipids, and derivatized spore-specific bacterial biomarker, 2,6-dipicolinic acid (DPA) as well as the lipopolysaccharide-amide-linked hydroxy-fatty acids (LPS-ALHFA) of Gram-negative bacteria. The extraction should take about an hour for each sample but multiple samples can be processed simultaneously.

Bioenergetics of the Archaea

In the late 1970s, on the basis of rRNA phylogeny, Archaea (archaebacteria) was identified as a distinct domain of life besides Bacteria (eubacteria) and Eucarya. Though forming a separate domain, Archaea display an enormous diversity of lifestyles and metabolic capabilities. Many archaeal species are adapted to extreme environments with respect to salinity, temperatures around the boiling point of water, and/or extremely alkaline or acidic pH. This has posed the challenge of studying the molecular and mechanistic bases on which these organisms can cope with such adverse conditions. This review considers our cumulative knowledge on archaeal mechanisms of primary energy conservation, in relationship to those of bacteria and eucarya. Although the universal principle of chemiosmotic energy conservation also holds for Archaea, distinct features have been discovered with respect to novel ion-transducing, membrane-residing protein complexes and the use of novel cofactors in bioenergetics of methanogenesis. From aerobically respiring Archaea, unusual electron-transporting supercomplexes could be isolated and functionally resolved, and a proposal on the organization of archaeal electron transport chains has been presented. The unique functions of archaeal rhodopsins as sensory systems and as proton or chloride pumps have been elucidated on the basis of recent structural information on the atomic scale. Whereas components of methanogenesis and of phototrophic energy transduction in halobacteria appear to be unique to Archaea, respiratory complexes and the ATP synthase exhibit some chimeric features with respect to their evolutionary origin. Nevertheless, archaeal ATP synthases are to be considered distinct members of this family of secondary energy transducers. A major challenge to future investigations is the development of archaeal genetic transformation systems, in order to gain access to the regulation of bioenergetic systems and to overproducers of archaeal membrane proteins as a prerequisite for their crystallization.

Molecular biology and genetics of mycoplasmas (Mollicutes)

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Characterization of Campylobacter jejuni/coli-isolates from human faeces

Campylobacter jejuni/coli strains were isolated from the faeces of 240 patients suffering from acute enteritis. The following characteristics were investigated: (i) growth at different temperatures, and on different substrates under either microaerophilic conditions or anaerobically, with fumarate or nitrate as terminal electron acceptors; (ii) production of H2S in cysteine-containing broth; (iii) hydrolysis of hippuric acid; (iv) DNase; (v) alkaline phosphatase; (vi) beta-lactamase; (vii) presence of menaquinone; and (viii) reduction of selenite. Based on characteristics (ii)-(v), the strains could be divided in 9 phenotypical groups. Most of the strains represented group 2 (DNase+, H2S+, hippurate hydrolysis+, alk. phosphatase-) (32%), and groups 8 (DNase-, H2S+, hippurate hydrolysis+, alk. phosphatase-) (32%). The other groups were of minor importance. On the other hand, most of the isolates from the United States (Weaver, 1981) fitted well into group 1 (DNase+, H2S+, hippurate hydrolysis+, alk. phosphatase+) which might demonstrate geographical variations among C. jejuni/coli.

Purification and properties of acetate kinase from Acholeplasma laidlawii

Acetate kinase (EC 2.7.2.1) was purified from Acholeplasma laidlawii cytoplasm by a combination of ammonium sulfate fractionation, gel filtration, diethylaminoethyl-cellulose chromatography, and affinity chromatography on 8-(6-aminohexylamino)-adenosine 5'-triphosphate conjugated to Sepharose 4B. The enzyme was composed of polypeptide chains of about 50,000 molecular weight as estimated from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Under nondenaturating conditions, apparent molecular weights between 64,000 and 130,000 were obtained, depending upon mainly the ionic strength of the test solution. The enzyme had a narrow specificity for phosphate acceptor acids, whereas both purine and pyrimidine nucleoside triphosphates were suitable phosphate donors. Na(+) and K(+) inhibited both acetyl phosphate and adenosine 5'-triphosphate synthesis, and the latter was also inhibited by high concentrations of adenosine 5'-diphosphate and acetyl phosphate. This substrate inhibition was partially abolished by 0.5 M NaCl. The enzyme catalyzed the independent adenosine 5'-diphosphate<-->adenosine 5'-triphosphate and acetate<-->acetyl phosphate exchanges. The rate of the latter was enhanced by the addition of cosubstrate Mg(2+)-adenosine 5'-triphosphate. The high affinity for substrates, except for acetate, indicated that under physiological conditions the direction of the enzymic reaction favors adenosine 5'-triphosphate synthesis. Thus, a mechanism for adenosine 5'-triphosphate generation in mycoplasmas is suggested.

Flagellation and swimming motility of Thermoplasma acidophilum

Electron microscopy of thin sections of Thermoplasma acidophilum confirmed previous observations of the absence of a typical cell wall in this organism. Negatively stained specimens revealed the almost consistent occurrence in both strains examined of monotrichously arranged flagella, about 9 micrometer long, which describe a sinuous curve with a wavelength of 1.5 to 2.0 micrometer and an amplitude of 0.33 to 0.59 micrometer. Motility of T. acidophilum could be demonstrated microscopically by microcinematography and macroscopically. The theoretical implications of the demonstration of functioning flagella in a wall-defective organism are discussed in the light of current theories of the mechanism of flagellar motility and from a taxonomic point of view.

The association of Mycobacterium flavum 301 with gram-negative bacteria: ultrastructural and biochemical evidence

Morphological characteristics, respiratory quinones, biochemical activities, cell wall ultrastructure and DNA base composition of Mycobacterium flavum 301 were studied. On the basis of the composition of its cell wall, its respiratory quinone and ubiquinone, the organism was associated with gram-negative bacteria. The strain appears to represent a group of bacteria hitherto not described.