Ectothiorhodospira vacuolata sp. nov., a new phototrophic bacterium from soda lakes

A new phototrophic bacterium was isolated from Jordanian and Kenyan alkaline salt lakes. Cells are rod shaped, 1.5 m wide and 2–4 m long, and motile by polar flagella. They divide by binary fission, and possess photosynthetic membranes as lamellar stacks similar to those in the other species of the genus Ectothiorhodospira and the brown colored Rhodospirillum species. The presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series is indicated by the absorption spectra of living cells. Under certain growth conditions the cells form gas vacuoles, may become immotile and float to the top of the culture medium. Sulfide and thiosulfate are used as photosynthetic electron donors. During the oxidation of sulfide to sulfate, elemental sulfur is formed, which is accumulated outside the cells. The organisms are strictly anaerobic, do not require vitamins, are moderately halophilic and need alkaline pH-values for growth. The new species Ectothiorhodospira vacuolata is proposed.     

Acetogenium kivui,a new thermophilic hydrogen-oxidizing acetogenic bacterium

Hydrogen-oxidizing acetogenic bacteria in pure culture are presently represented by the two mesophilic species, Acetobacterium woodii and Clostridium aceticum. From Lake Kivu we have isolated a Gram negative, chemolithotrophic, thermophilic anaerobe (LKT-1) that oxidizes hydrogen and reduces carbon dioxide to acetic acid. It is a non-motile, non-sporeforming rod, about 0.7m in width and 2–7.5m in length, often occuring in pairs or chains. The cell wall has a banded appearance; the surface layer contains a regular array of particles with six-fold rotational symmetry. No outer membrane is present. The temperature optimum for growth is 66°C, and the pH optimum is 6.4. Organic growth substrates include glucose, mannose, fructose, pyruvate, and formate; acetate is the principal product. The doubling time for growth on hydrogen and carbon dioxide is about 2h. Vitamins are neither required nor stimulatory. Yeast extract and Trypticase enhance the final yield but do not affect the growth rate. Cysteine or sulfide are required and cannot be replaced by thioglycolate or dithiothreitol. LKT-1 was mass cultured on hydrogen and carbon dioxide in a 24.1 fermentor with a yield of 34g (wet weight) of cells. The DNA base composition as determined by buoyant density is 38 mol % guanine plus cytosine. LKT-1 appears only distantly related to physiologically similar bacteria. A new genus Acetogenium is proposed, and the species is Acetogenium kivui.     

Acetate uptake by the unicellular cyanobacteria Synechococcus and Aphanocapsa

Acetate uptake by strains of Synechococcus and Aphanocapsa in short experiments required light, and was strongly inhibited by m-dichlorocarbonyl cyanide phenylhydrazone and dichlorophenyl dimethyl urea. Acetate carbon was distributed in amino acids and in the acyl portion of lipids in the same way as during growth experiments when CO₂ was available, but the reduced incorporation in the absence of CO₂ was primarily into the lipid fraction. An apparent K _m for uptake by Synechococcus and for Aphanocapsa 6308 of 20 and 180 M at pH 7.4 was obtained; corresponding V _max values were 6 and 11 nmol x min^-1 x mg protein^-1. Uptake with Synechococcus was affected by pH, with affinity decreased and maximal rate increase with rising pH. Acetate uptake was not affected by propionate or butyrate when both were added at the same time, but a light and concentration dependent inhibition developed if suspensions were preincubated with propionate. Acetate carbon moved rapidly into acid insoluble material, but after 10–15 s 75% or more of the recovered intracellular counts were in acetyl CoA. Counts in this compound were reduced by preincubation with propionate.Kinetic measurements of acetyl CoA synthetase in fractionated cell extracts gave values for K _m of about 50 M for acetate, 5 mM for propionate, 100 M for CoA and 0.38 mM for ATP. The internal pool of free CoA was measured to be about 20 M, and was reduced by preincubation with propionate. This suggests that the activity of CoA-mediated reactions may be regulated by the availability of this cofactor.Abbreviations Used CCCP m-Dichlorocarbonyl cyanide phenyl hydrazone - DCMU dichlorophenyl dimethyl urea - TCA trichloroacetic acid - Tris trishydroxymethyl amino methane - HEPES N-2-hydroxyethylpiperazine-N-2-ethane-sulfonic acid     

Transition of Thiobacillus ferrooxidans KG-4 from heterotrophic growth on glucose to autotrophic growth on ferrous-iron

The reputedly obligately organotrophic Thiobacillus ferrooxidans KG-4 cultured on glucose contained a small proportion of cells which grew autotrophically on ferrous-iron.     

Sulphite oxidation by mitochondria from green and etiolated peas

Sulphite oxidation by mitochondria prepared from green pea epicotyls had a higher K_m than did the sulphite oxidation of mitochondria prepared from etiolated pea epicotyls. Mitochondrial sulphite oxidation from green and etiolated tissues was inhibited by cyanide but not by azide, rotenone, antimycin A or oligomycin. Mitochondria from green and etiolated tissues were able to oxidize glyoxal-bisulphite, but not as effectively as sulphite.     

Mass spectrometric measurements of methane and oxygen utilization by methanotrophic bacteria

Abstract A mass spectrometer with membrane inlet was used to measure methane and oxygen utilization rates at various methane concentrations in Methylosinus trichosporium and a locally isolated strain of a methane-oxidizing coccus (OU-4-1). The apparent K _m for methane was found to be 2 μM for M. trichosporium and 0.8 μM for strain OU-4-1. These K _m-values are 10–30 times lower than most previously reported values. The ratio of oxygen to methane utilization rates was 1.7 for M. trichosporium and 1.5 for strain OU-4-1 corresponding to a growth yield of 0.38 and 0.63 g dry weight/g methane, respectively.     

Stimulation by interferon of induction of differentiation of human promyelocytic leukemia cells

F₁-ATPase was isolated from yeast $\text{S.}\text{cerevisiae}$. The constituent subunits 1 and 2 were purified by gel permeation chromatography, and their amino acid compositions determined. Both subunits have a similar composition except for $\text{1}\text{2}$ cystine, methionine, leucine, histidine, and tryptophan. When F₁ is treated for three hours with 5′-p-[³H]fluorosulfonylbenzoyl adenosine in dimethylsulfoxide, 90% of the activity is lost. Disc gel electrophoresis of the modified complex showed that over 90% of the label was associated with subunit 2. A labelled peptide from a $\text{S.}\text{aureus}$ digest of subunit 2 was isolated and sequenced. It had the following amino acid sequence: His-Try¹-Asp-Val-Ala-Ser-Lys-Val-Gln-Glu, whereby Tyr¹ is the modified amino acid residue. This sequence shows homology to other sequences obtained from maize, beef heart, and $\text{E.}\text{coli}$ F₁-ATPases.     

Unsaturated fatty acid-dependent oxidation of epinephrine in homogenates of the gorgonian, Pseudoplexaura porosa

A novel epinephrine oxidation system in homogenates of the gorgonian Pseudoplexaura porosa was discovered. The enzymatic reaction required an unsaturated fatty acid and molecular oxygen or hydrogen peroxide. Diphenylisobenzofuran was also oxidized by Ps. porosa homogenates in the presence of an unsaturated fatty acid. Hydroxyl radical and superoxide anion did not appear to be involved in either of these oxidative reactions. The production of lipid hydroperoxides was not necessary for epinephrine oxidation and, with the exception of arachidonic acid, lipid hydroperoxide production did not occur. Evidence is presented for the involvement of singlet oxygen or a similar activated oxygen intermediate in the reactions, and a possible mechanism was proposed. The use of arachidonate-dependent epinephrine oxidation as a measure of prostaglandin synthetase activity is criticized.     

Relative contributions of biological and chemical reactions to the overall rate of pyrite oxidation at temperatures between 30 degrees C and 70 degrees C

The stoichiometry and kinetics of the spontaneous, chemical reaction between pyrite and ferric iron was studied at 30, 45, and 70 degrees C in shake flasks at pH 1.5 by monitoring the ferrous iron, total iron, elemental sulfur, and sulfate concentration profiles in time. It was found that the sulfur moiety of pyrite was oxidized completely to sulfate. Elemental sulfur was not produced in detectable amounts. The iron moiety of pyrite was released as ferrous iron. All observed initial reaction rates could be fitted into an empirical equation. This equation includes the concentrations of ferric iron and pyrite, and a constant which is dependent on the temperature and the nature of the main anion present. It was observed that ferrous iron formed during the reaction slowed down the oxidation of pyrite by ferric iron. The extent of this effect decreased with increasing temperature. With the aid of the empirical equation, the contribution of the chemical oxidation of pyrite by ferric iron to the overall oxidation in a hypothetical plug-flow reactor, in which biologically mediated oxdidation of pyrite and ferrous iron by oxygen also takes place, can be assessed. At 30, 45, and 70 degrees C, respectively, 2, 8-17, and 43% of the pyrite was oxidized chemically by ferric iron. Therefore, it is expected that only in reactors operating at high temperatures with extremely thermophilic bacteria, will chemical oxidation cause a significant deviation from the apparent first order overall kinetics of biological pyrite oxidation.     

Expression of streptomycete cholesterol oxidase inEscherichia coli

Summary A streptomycete gene coding for extracellular cholesterol oxidase (choA) was subcloned and expressed inEscherichia coli. The pUCO series recombinants were obtained by inserting thechoA gene into the uniqueKpnI site of pUC19 vector. Expression was observed with pUCO192A and pUCO193 constructs in which the cloned gene(s) were aligned with the upstreamlacZ promoter. Isopropyl -d-thioglucopyranoside (IPTG) enhanced this expression up to 2.5-fold. Specific Cho activity in the cell extracts of the stable pUCO193 transformant were 0.004 U and 0.007 U per mg protein without and with IPTG induction, respectively. Cho activity was detected in the spent medium of this culture, suggesting possible secretion of the enzyme.