The immunosuppressant SR 31747 blocks cell proliferation by inhibiting a steroid isomerase in Saccharomyces cerevisiae.

SR 31747 is a novel immunosuppressant agent that arrests cell proliferation in the yeast Saccharomyces cerevisiae, SR 31747-treated cells accumulate the same aberrant sterols as those found in a mutant impaired in delta 8- delta 7-sterol isomerase. Sterol isomerase activity is also inhibited by SR 31747 in in vitro assays. Overexpression of the sterol isomerase-encoding gene, ERG2, confers enhanced SR resistance. Cells growing anaerobically on ergosterol-containing medium are not sensitive to SR. Disruption of the sterol isomerase-encoding gene is lethal in cells growing in the absence of exogenous ergosterol, except in SR-resistant mutants lacking either the SUR4 or the FEN1 gene product. The results suggest that sterol isomerase is the target of SR 31747 and that both the SUR4 and FEN1 gene products are required to mediate the proliferation arrest induced by ergosterol depletion.

Spirochaeta smaragdinae sp. nov., a new mesophilic strictly anaerobic spirochete from an oil field.

An obligately anaerobic spirochete designated strain SEBR 4228T (T = type strain) was isolated from an oil field of Congo, Central Africa. The strain grew optimally with a sodium chloride concentration of 5% (sodium chloride concentration) growth range 1.0-10%) at 37 degrees C (growth temperature range 20-40 degrees C) and pH of 7.0-7.2 (pH growth range pH 5.5-8.0). Strain SEBR 4228T grew on carbohydrates (glucose, fructose, ribose, D-xylose, galactose, mannitol and mannose), glycerol, fumarate, peptides and yeast extract. Yeast extract was required for growth and could not be replaced by vitamins. It reduced thiosulfate and sulfur, to H2S. Glucose was oxidised to lactate, acetate, CO2 and H2S in the presence of thiosulfate but in its absence lactate, ethanol, CO2 and H2 were produced. Fumarate was fermented to acetate and succinate. The G + C content of strain SEBR 4228T was 50%. Strain SEBR 4228T was spiral shaped measuring 5-30 by 0.3-0.5 micron and was motile with a corkscrew-like motion. Electron microscopy revealed the presence of periplasmic flagella in a 1-2-1 arrangement. Strain SEBR 4228T possessed features typical of the members of the genus Spirochaeta. 16S rRNA sequence analysis revealed that it was closely related to Spirochaeta bajacaliforniensis (similarity 98.6%). The lack of DNA homology with S. bajacaliforniensis (38%), together with other phenotypic differences, indicated that strain SEBR 4228T is a new species, which we have designated Spirochaeta smaragdinae. The type strain is SEBR 4228T (= DSM 11293).

Biodegradation of refractory hydrocarbon biomarkers from petroleum under laboratory conditions.

Biomarkers are of great value in petroleum exploration because they provide essential information about the geological history of oils and source rocks. Steranes are of particular importance as they can be related to naturally occurring precursors. These compounds generally experience intense biodegradation, however, which alters their original distribution and obscures the information that they carry regarding oil maturity and source material. In an attempt to identify the microorganisms responsible for this degradation, we have investigated the capacity of 73 aerobic bacteria to degrade steranes present in Rozel Point (Utah) oil. Seven Gram-positive strains, belonging to a limited number of genera, were found to be active. Using Nocardia sp. SEBR 16, which caused the most extensive alteration, we have determined biodegradation rates for several isomers of steranes and methylsteranes. The preference for alteration of different isomers reflects that observed in natural environments, suggesting that the degradation intermediates could be used as indicators of the extent of the biodegradation in an oil. In addition, the microorganisms used here might be effective in biodegrading oil spills.

[Beta-lactamase induction in Pseudomonas aeruginosa by cefpiramide and 3 other antipyocyanic cephalosporins]. / Etude de l'induction de bêta-lactamase chez Pseudomonas aeruginosa par le cefpiramide et trois autres céphalosporines antipyocyaniques.

Cefpiramide (SR 95445) (CPM) is a new cephalosporin with activity against Pseudomonas and a good bioavailability following parenteral administration. This drug is a first rather than second choice treatment in Pseudomonas infections. For this reason, investigation into cefpiramide's capacity to induce beta-lactamase production is especially interesting. A heavy inoculum of P. aeruginosa NCTC 8203, a strain that produces and inducible cephalosporinase (pI = 8.7) was incubated for 4 hours with CPM, cefsulodin (CFS), cefoperazone (CPZ) and ceftazidime (CTZ) in various concentrations. After collection and sonic treatment of the bacteria, the beta-lactamase activity was assayed using an acidimetric method and expressed as units of enzyme activity per mg proteins in the cell-free extract. The smallest increase in beta-lactamase production was recorded with CPM. The strongest inductor was CTZ. CFS and CPZ had an intermediate effect.

Characterization of sulfate-reducing bacteria isolated from oil-field waters.

The occurrence and metabolic capacities of sulfate-reducing bacteria (SRB) were studied in 23 water samples taken from producing wells at 14 different sites. Oil fields in France, the North Sea, and the Gulf of Guinea were selected and classified according to physicochemical parameters (salinity ranging from 0.3 to 120 g.L-1 and temperature between 29 and 85 degrees C). After the distribution of SRB within oil fields was studied, several strains of SRB were isolated and characterized metabolically. Twenty of the thirty-seven strains were not related to any known species. Most of the identified strains were members of the genera Desulfovibrio and Desulfotomaculum by molecular, morphological, and physiological properties.

Antiproliferative effects of SR31747A in animal cell lines are mediated by inhibition of cholesterol biosynthesis at the sterol isomerase step.

SR31747A is a new sigma ligand exhibiting immunosuppressive properties and antiproliferative activity on lymphocyte cells. Only two subtypes of sigma receptor, namely the sigma1 receptor and emopamil-binding protein, have been characterised molecularly. Only the sigma1 receptor has been shown to bind (Z)N-cyclohexyl-N-ethyl-3-(3-chloro4-cyclohexylphenyl)pro pen-2-ylamine hydrochloride (SR31747A) with high affinity. It was demonstrated that the SR31747A effect on the inhibition of T-cell proliferation was consistent with a sigma1 receptor-mediated event. In this report, binding experiments and sterol isomerase assays, using recombinant yeast strains, indicate that the recently cloned emopamil-binding protein is a new SR31747A-binding protein whose activity is inhibited by SR31747A. Sterol analyses reveal the accumulation of a delta8-cholesterol isomer at the expense of cholesterol in SR31747A-treated cells, suggesting that cholesterol biosynthesis is inhibited by SR31747A at the delta8-delta7 sterol isomerase step in animal cells. This observation is consistent with a sterol isomerase role of the emopamil-binding protein in the cholesterol biosynthetic pathway in animal cells. In contrast, there is no evidence for such a role of the sigma1 receptor, in spite of the structural similarity shared by this protein and yeast sterol isomerase. We have found that SR31747A also exerts anti-proliferative effects at nanomolar concentrations on various established cell lines. The antiproliferative activity of SR31747A is reversed by cholesterol. Sterol-isomerase overproduction enhances resistance of CHO cells. This last observation strongly suggests that sterol isomerase is implicated in the antiproliferative effect of the drug in established cell lines.