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L I Hochstein

Publications and source records attributed to L I Hochstein.

At least 37 records · Page 2Linked to original sources
PubMed1986

Halobacterium denitrificans sp. nov., an extremely halophilic denitrifying bacterium.

Halobacterium denitrificans was one of several carbohydrate-utilizing, denitrifying, extremely halophilic bacteria isolated by anaerobic enrichment in the presence of nitrate. Anaerobic growth took place only when nitrate (or nitrite) was present and was accompanied by the production of dinitrogen. In the presence of high concentrations of nitrate (i.e., 0.5%), nitrous oxide and nitrite were also detected. When grown aerobically in a mineral-salts medium containing 0.005% yeast extract, H. denitrificans utilized a variety of carbohydrates as sources of carbon and energy. In every case, carbohydrate utilization was accompanied by acid production. A type culture has been deposited with the American Type Culture Collection, Rockville, Md. (ATCC 35960).

Anaerobiosis↗
PubMed1986

The occurrence of denitrification in extremely halophilic bacteria.

The ability of Halobacterium vallismortis, Halobacterium mediterranei and Halobacterium marismortui (Ginzburg strain) to grow anaerobically and denitrify was determined. Each organism grew anaerobically only in the presence of nitrate. H. marismortui produced nitrite and dinitrogen from nitrate during exponential growth. However, as the culture entered stationary phase, dinitrogen production ceased and nitrous oxide was detected. H. vallismortis produced nitrous oxide and dinitrogen during exponential growth, with dinitrogen production ceasing at the onset of stationary phase. H. mediterranei produced dinitrogen during exponential growth and did not produce nitrous oxide. These results confirm the occurrence of denitrification in the halobacteria.

Anaerobiosis↗
PubMed1986

Trypsin digestion for determining orientation of ATPase in Halobacterium saccharovorum membrane vesicles.

Membranes prepared by low pressure disruption of cells exhibited no ATPase activity in the absence of Triton X-100, although 43% of the total menadione reductase activity was detected. Trypsin digestion reduced menadione reductase activity by 45% whereas ATPase activity was not affected. Disruption of the membrane fraction at higher pressure solubilized about 45% of the ATPase activity. The soluble activity was still enhanced by Triton X-100, suggesting that the detergent, besides disrupting membrane vesicles, also activated the ATPase. The discrepancy in localization of menadione reductase and ATPase activities raised questions regarding the reliability of using a single marker enzyme as an indicator of vesicle orientation.

Adenosine Triphosphatases↗
PubMed1985

Dicyclohexylcarbodiimide-sensitive ATPase in Halobacterium saccharovorum.

Membranes from Halobacterium saccharovorum contained a cryptic ATPase which required Mg2+ or Mn2+ and was activated by Triton X-100. The optimal pH for ATP hydrolysis was 9-10. ATP or GTP were hydrolyzed at the same rate while ITP, CTP, and UTP were hydrolyzed at about half that rate. The products of ATP hydrolysis were ADP and phosphate. The ATPase required high concentrations (3.5 M) of NaCl for maximum activity. ADP was a competitive inhibitor of the activity, with an apparent Ki of 50 microM. Dicyclohexylcarbodiimide (DCCD) inhibited ATP hydrolysis. The inhibition was marginal at the optimum pH of the enzyme. When the ATPase was preincubated with DCCD at varying pH values, but assayed at the optimal pH for activity, DCCD inhibition was observed to increase with increasing acidity of the preincubation medium. DCCD inhibition was also dependent on time of preincubation, and protein and DCCD concentrations. When preincubated at pH 6.0 for 4 h at a protein:DCCD ratio of 40 (w/w), ATPase activity was inhibited 90%.

Adenosine Diphosphate↗
PubMed1985

Denitrification by extremely halophilic bacteria.

Extremely halophilic bacteria were isolated from widely separated sites by anaerobic enrichment in the presence of nitrate. The anaerobic growth of several of these isolates was accompanied by the production of nitrate, nitrous oxide, and dinitrogen. These results are a direct confirmation of the existence of extremely halophilic denitrifying bacteria, and suggest that such bacteria may be common inhabitants of hypersaline environments.

Anaerobiosis↗
PubMed1984

The effect of oxygen on denitrification during steady-state growth of Paracoccus halodenitrificans.

Steady-state cultures of Paracoccus halodenitrificans were grown anaerobically prior to establishing steady states at different concentrations of oxygen. In the absence of oxygen, nitrate-limited cultures produced dinitrogen, and as the oxygen supply increased, these cultures produced nitrous oxide, then nitrite. These changes reflected two phenomena: the inactivation of nitrous oxide reductase by oxygen and the diversion of electrons from nitrite to oxygen.

Aerobiosis↗
PubMed1984

A dissimilatory nitrite reductase in Paracoccus halodenitrificans.

Paracoccus halodenitrificans produced a membrane-associated nitrite reductase. Spectrophotometric analysis showed it to be associated with a cd-cytochrome and located on the inner side of the cytoplasmic membrane. When supplied with nitrite, membrane preparations produced nitrous oxide and nitric oxide in different ratios depending on the electron donor employed. The nitrite reductase was maximally active at relatively low concentrations of sodium chloride and remained attached to the membranes at 100 mM sodium chloride.

Cell Membrane↗
PubMed1984

Electron transport in Paracoccus halodenitrificans and the role of ubiquinone.

The membrane-bound NADH oxidase of Paracoccus halodenitrificans was inhibited by dicoumarol, 2-n-heptyl-4-hydroxy-quinoline-N-oxide (HQNO), and exposure to ultraviolet light (at 366 nm). When the membranes were extracted with n-pentane, NADH oxidase activity was lost. Partial restoration was achieved by adding the ubiquinone fraction extracted from the membranes. Succinate oxidation was not inhibited by dicoumarol or HQNO, but was affected by ultraviolet irradiation or n-pentane extraction. However, the addition of the ubiquinone fraction to the membranes extracted with n-pentane did not restore enzyme activity. These observations suggested that NADH and succinate were not oxidized through a common ubiquinone pool.

Dicumarol↗
PubMed1984

The growth of Paracoccus halodenitrificans in a defined medium.

A synthetic medium, consisting of inorganic salts and any of a number of carbon sources, supported the aerobic growth of Paracoccus halodenitrificans when supplemented with thiamine. The same medium plus an appropriate nitrogenous oxide supported anaerobic growth when additionally supplemented with methionine. The observation that vitamin B12 or betaine replaced methionine suggested that P. halodenitrificans had a defect in the cobalamin-dependent pathway for methionine biosynthesis, as well as the inability to synthesize betaine when growing anaerobically.

Ammonium Sulfate↗
PubMed1980

The intracellular Na+ and K+ composition of the moderately halophilic bacterium, Paracoccus halodenitrificans.

The intracellular concentrations of Na+ and K+ in exponentially growing Paracoccus halodenitrificans were independent of the NaCl concentration of the growth medium. The observed values were approximately 100 and 300 mM for Na+ and K+, respectively. In stationary phase cells, the ultimate values for Na+ depended on the NaCl concentration of the growth medium. With cells grown in the presence of 1 M NaCl, the value was about 500 mM; for cells grown in the presence of 3 M NaCl, the value was about 1.1 M. The K+ concentration in stationary phase cells was unaffected by the NaCl concentration in the growth medium. The final value was about 100 mM. Associated with these changes were changes in the ATP pool and decreases in the activities of the NADH oxidase system and the membrane-bound ATPase. It is proposed that the decrease in the activities of these enzymes may account for the ion flows observed in stationary phase cells.

Adenosine Triphosphatases↗
PubMed1978

The metabolism of carbohydrates by extremely halophilic bacteria: the identification of lactobionic acid as a product of lactose metabolism by Halobacterium saccharovorum.

Nongrowing cells of Halobacterium saccharovorum oxidized lactose to a product identified as lactobionic acid by thin-layer, paper, and column chromatography, and by identification of the galactose and gluconic acid produced from it after acid hydrolysis. Growing cells oxidized lactose to a product that was identical with lactobionate except that it did not serve as a substrate for galactose oxidase. While the identity of this compound has not been established, it is suggested that the product is lactobionic acid in which the galactose moeity is in the furanose form. Neither lactobionate nor the product produced by growing cells was further metabolized, suggesting that lactose oxidation is not coupled to growth.

Cells, Cultured↗
PubMed1976

Halobacterium saccharovorum sp. nov., a carbohydrate-metabolizing, extremely halophilic bacterium.

The previously described extremely halophilic bacterium, strain M6, metabolizes a variety of carbohydrates with the production of acid. In addition, the organism produces nitrite (but no gas) from nitrate, is motile, and grows most rapidly at about 50 degrees C. These characteristics distinguish it from all previously described halophilic bacteria in the genus Halobacterium. It is suggested that it be designated as a new species, Halobacterium saccharovorum.

California↗
PubMed1976

The metabolism of carbohydrates by extremely halophilic bacteria: identification of galactonic acid as a product of galactose metabolism.

Cell-free extracts prepared from the extremely halophilic bacterium Halobacterium saccharovorum oxidize galactose and accumulate a product which reacts as if it were a lactone. The product does not act as a reducing sugar and contains all six of the carbon atoms initially present in galactose. The product was jugged to be galactonic acid, based on the behavior of the acetylmethyl ester derivative of the product and the pentaacetyl derivative of the galactonic methyl ester during gas chromatography.

Alcohol Oxidoreductases↗
PubMed1975

Studies of a halophilic NADH dehydrogenase. II. Kinetic properties of the enzyme in relation to salt activation.

1. An NADH dehydrogenase, obtained from an extremely halophilic bacterium, was activated by various salts when enzyme activity was measured as the observed velocity, whereas the maximum velocity was unaffected by either the salt concentration or the nature of the salt. 2. Two ion effects were observed; a quantitative cation effect, reflected in changes in the apparent Michaelis constant for 2,6-dichlorophenolindophenol, and a qualitative anion effect, reflected in the apparent Michaelis and dissociation constants for NADH. 3. The data suggest that cations act by neutralizing electrostatic charges surrounding the 2,6-dichlorophenolindophenol-binding site, whereas the anions affect the conformation of the enzyme by altering the accessibility of the NADH-binding site to the bulk solvent. 4. Thus, the apparent activation of this enzyme, obtained from an extremely halophilic bacterium, is a reflection of measuring enzyme activity at non-saturating substrate concentrations.

2,6-Dichloroindophenol↗
PubMed1972

A salt-inhibited cytochrome c reductase obtained from the moderately halophilic bacterium, Micrococcus halodenitrificans.

A membrane-bound cytochrome c reductase from Micrococcus halodenitrificans was inhibited by NaCl at concentrations as low as 0.05 m. The inhibition was competitive with respect to cytochrome c and noncompetitive with respect to reduced nicotinamide adenine dinucleotide. Thus the effect of NaCl was to increase the apparent K(m) of the enzyme for cytochrome c and not to inhibit the intrinsic activity of the enzyme.

Cell Membrane↗