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Biomedical subjects

D J Kushner

Publications and source records attributed to D J Kushner.

At least 55 records · Page 3Linked to original sources
PubMed1975

Influence of temperature and salt concentration on the growth of a facultatively halophilic "Micrococcus" sp.

Growth characteristics of a facultatively halophilic strain of Micrococcus, capable of growth in medium containing no added NaCl and in medium containing 5.5 M NaCl, were studied over a range of salt concentrations and temperatures. Optimal growth occurred at 35C in a medium containing 1.0 M NaCl. In a medium containing 0.1 M NaCl, growth only occurred if the incubation temperature was less than 30C. No growth occurred if KCl, LiCl, NH4Cl, MgCl2, or sucrose was substituted for NaCl at 35C. A reexamination of bacteria previously described as moderate halophiles is suggested.

Ammonium Chloride↗
PubMed1975

Lipase and esterase formation by psychrophilic and mesophilic Acinetobacter species.

Acinetobacter O16, a psychrophilic species, produced extracellular lipase (measured by hydrolysis of olive oil, tributyrin, or beta-naphthyl laurate) when grown on a complex medium (peptone plus yeast extract). Most lipase was produced during the logarithmic phase of growth. Very little cell-bound lipase was formed. These cells also produced an esterase (measured by the hydrolysis of beta-naphthyl acetate). At first, all esterase was cell bound; significant amounts appeared in the external medium late in growth. Breaking the cells did not increase cell-bound lipase activity. After breaking of the cells, most of the cell-bound lipase and esterase activity was solubilized, even after very high speed centrifugation. No appreciable amounts of these enzymes were released by osmotic shock. Lipase formation was greatly affected by nutrient conditions. Lowering either the yeast extract of the peptone content of the normal complex medium lowered or abolished lipase formation. Esterase activity was lowered to a lesser extent. Cells growing in synthetic amino acid plus vitamin medium or in acid-hydrolyzed casein produced substantial amounts of esterase but no cell-free or cell-bound lipase. However, if sodium taurocholate was added to these media, lipase was produced. Greatest production occurred if a mixture of di- and poly-peptides was also present. Taurocholate also stimulated lipase production in the normal complex medium. Adding Tween 80 or ethanol to the normal complex medium inhibited lipase production. Sodium acetate, oleic acid, olive oil, or Tween 20 added to synthetic media did not affect lipase production. The psychrophile grew more quickly at 30 degrees C than at 15 or 20 degrees C but produced more lipase at the lower temperatures. Esterase production was about the same at 20 and 30 degrees C. A mesophilic Acinetobacter species produced the same amount of lipase and esterase at 20 and 30 degrees C. The best production of lipase by the psychrophile occurred in standing cultures.

Acinetobacter↗
PubMed1975

Partial purification and characterization of the lipase of a facultatively psychrophilic bacterium (Acinetobacter O16).

The extracellular lipase(s) of the psychrophile Acinetobacter O16 was studied. When the enzyme was precipitated by (NH4)2SO4 and passed through a Sephadex G200 column, two peaks of lipase activity appeared. The larger peak, which behaved like a substance of high molecular weight, being eluted in the void volume, was purified 250-fold over the crude enzyme (culture supernatant) by passage through a DEAE-Sephadex column. When the enzyme was applied to a DEAE-cellulose column it could not be eluted unless it had first been treated with the detergent Titon X 100. It is suggested that lipids or phospholipids make up an important part of the molecule. The activity of the crude and partly purified enzymes was studied in relation to pH and temperature optima. Lipases from the psychrophilic Acinetobacter O16 and from the mesophilic Acinetobacter O4 reacted in the same way to temperature. The crude enzyme from Acinetobacter O16 was more temperature-stable than the purified enzyme.

Acinetobacter↗
PubMed1975

Isolation and characterization of Actinopolyspora halophila, gen. et sp. nov., an extremely halophilic actinomycete.

An actinomycete, isolated as a contaminant of a culture medium containing 25% NaCl, has been classified as Actinopolyspora halophila gen. et sp. nov. in the family Nocardiaceae. The morphology and biochemical characteristics of this organism distinguish it from other members of the family Nocardiaceae and other genera possessing a type IV cell wall. It requires high NaCl concentrations for growth and can grow in saturated NaCl. The lowest concentration permitting growth in liquid medium is 12%, and on solid medium, 10%. Colonies developing at lower salt concentrations contain holes resembling viral plaques. No growth occurred in a medium containing 30% KCl instead of NaCl. This organism can grow in simple media with NH4+ salts as nitrogen source and different sugars and other compounds as carbon source. Though it has a salt requirement almost as great as the extremely halophilic rods and cocci, it differs from these in containing diaminopimelic acid and in sensitivity to lysozyme; both properties suggest that it has a mucopeptide cell wall. It also contains some phospholipids common to other actinomycetes, but does not contain any phytanyl ether linked lipids characteristic of other extremely halophilic bacteria.

Cell Wall↗
PubMed1975

Characteristics of a facultatively psychrophilic Acinetobacter species isolated from river sediment.

A facultatively psychrophilic bacterium isolated from river sediment was identified as an Acinetobacter species, similar to those previously characterized as A. lwoffi. The strain was extremely lipolytic and hemolytic. Some action on crude oil was also observed. The organism was able to utilize a wide variety of carbon and energy sources when tested at both 20 and 30 degrees C. A comparison is made with the previously proposed type strain of A. lwoffi. The bacteria had a Gram-negative cell wall containing an electron-dense intermediate layer. Cell division occurred with the formation of a septum and slight constriction.

Acinetobacter↗
PubMed1973

Effects of energy metabolism on the release of bound proflavine from sensitive and resistant Escherichia coli.

Proflavine inhibited the aerobic and anaerobic utilization of glucose by sensitive but not by resistant Escherichia coli. In resistant cells that had bound proflavine, glucose utilization was accompanied by release of the dye. After glucose was used up, the cells could again take up proflavine. If the amount of proflavine bound to sensitive cells was too low to inhibit glucose utilization, adding glucose to these cells caused them to release the dye. With higher proflavine concentrations, inhibitory to glucose utilization, the dye remained cell bound. Thus, metabolic energy causes the release of proflavine by both sensitive and resistant cells. In the former, energy production is inhibited by proflavine, and thus the dye prevents its own release. Chloramphenicol did not interfere with metabolically induced release of proflavine from resistant cells. Cyanide inhibited the glycerol-induced loss of proflavine, but not the glucose-induced loss. Azide and carbonyl cyanide m-chlorophenylhydrazone could prevent proflavine release without inhibiting glucose utilization.

Acridines↗
PubMed1973

Kinetics and regulation of the salt-dependent aspartate transcarbamylase of Halobacterium cutirubrum.

Properties of the aspartate transcarbamylase of the extremly halophilic bacterium Halobacterium cutirubrum, an enzyme that needs high salt concentrations for activity and regulation, were studied in cell-free extracts. The enzyme was stable on prolonged incubation at 4 C in concentrated extracts (50 mg of protein per ml) but not in diluted extracts. Mg(2+) ions and beta-mercaptoethanol stabilized enzyme activity. At salt concentrations below the maximum for activity (3.5 m), the enzyme was rapidly inactivated. Carbamyl phosphate stabilized the enzyme under these conditions; aspartate had a smaller effect. The enzyme was most stable at 0 C; raising or lowering the temperature from this point increased the rate of inactivation. On exposure to lowered salt concentrations, enzyme activity was more sensitive than feedback inhibition. Hyperbolic substrate saturation curves were found for carbamyl phosphate. The K(m) obtained varied with the salt concentration used. With aspartate, sigmoidal curves were found when extracts were assayed immediately after preparation, but hyperbolic curves were obtained with extracts allowed to stand 1 to 2 hr. The presence of cytidine triphosphate (CTP) decreased the V(max) but did not change the K(m); this is thus a V-type enzyme. Low concentrations of succinate activated the enzyme, in the presence and absence of CTP; higher concentrations did not affect its activity. CTP increased the activation energy of the enzyme in 3.5 m salt but decreased it in 2.0 m salt. At both salt concentrations, the sensitivity of the enzyme to feedback inhibition diminished with increasing temperatures. Gel chromatography suggested that the enzyme in crude extracts had a molecular weight of 160,000. Precipitating the enzyme with polyethylene glycol decreased the molecular weight to 34,000, and this activity was no longer sensitive to CTP. The presence of either substrate of the enzyme during polyethylene glycol treatment prevented dissociation of the enzyme and loss of feedback inhibition. Thus, as with other aspartate transcarbamylases, association of subunits seems to be required for regulation of activity by end product.

Allosteric Regulation↗
PubMed1972

The elusive permeability barriers and binding sites for proflavine in Escherichia coli.

Cells of proflavine-sensitive and -resistant Escherichia coli strains were altered in different ways, and the proflavine binding of the changed material was studied. Spheroplasts prepared from sensitive and resistant cells bound similar amounts of proflavine at saturation, whether or not they were osmotically protected by 10% sucrose. Intact cells bound approximately the same amounts of proflavine as spheroplasts. On addition of glucose, osmotically protected resistant but not sensitive spheroplasts released proflavine; unprotected spheroplasts did not release bound proflavine. Thus, osmotically protected membranes are not required for proflavine binding (a passive process) but are required for proflavine release (an active process). The presence of sucrose reduced proflavine binding by resistant cells. Adding glucose to cells in 20% sucrose did not cause a release of residual proflavine, though glucose caused a release of proflavine from cells suspended in 0 or 10% sucrose. On treatment of heated cells or ruptured spheroplasts with nucleases and Pronase, practically all nucleic acids were removed. Proflavine-binding ability of such preparations fell by only 30 to 50%. Washing heated cells with ethanol did not reduce their proflavine-binding ability. There appear to be important binding sites in cells aside from nucleic acids.

Acridines↗
PubMed1972

Vibrio psychroerythrus sp. n.: classification of the psychrophilic marine bacterium, NRC 1004.

A red-pigmented organism, formerly known as marine psychrophile NRC 1004, has been classified as Vibrio psychroerythrus sp. n. Classification was mainly based on morphology, the ability of the organism to oxidize and ferment glucose, its sensitivity to vibriostat 0/129, and its deoxyribonucleic acid base composition of 40.0 moles% guanine plus cytosine, determined by thermal denaturation. The organism gave positive reactions for catalase, oxidase, and starch hydrolysis and produced acid from maltose and dextrin but not from arabinose. It was indole- and citrate-negative and reduced nitrate to nitrite without producing gas.

Acids↗
PubMed1971

Structural changes during lysis of a psychorophilic marine bacterium.

The marine psychrophile, a red, gram-negative motile rod with a single polar flagellum, is stable when suspended in 0.1 m Mg(2+) plus 0.5 m NaCl at 0 C and neutral pH but lyses if the salt composition of the medium is changed, the temperature raised above 20 C, or the pH lowered. Lysis is accompanied by a fall in turbidity, a release of ultraviolet-absorbing substances, and a loss of deoxyribonucleic acid and ribonucleic acid. Ultrastructural changes accompanying lysis were studied. Thin sections of cells fixed while intact showed a triple-layered cell wall and cytoplasmic membrane, each 6.0 to 7.5 nm thick. Mesosomes were also observed. Either Na(+) or Mg(2+) could maintain wall integrity, whereas Mg(2+) was needed for membrane integrity. In distilled water, lysis was very extensive, and much material was released as wall fragments and as vesicles which probably came from the wall and cytoplasmic membrane. Lysis at 37 C resulted in degradation of the wall and liberation of wall fragments. The cell membrane was rarely observed as a triple-layered structure in such temperature-lysed cells. After lysis at pH 5.0, the cell wall was distorted, and only a suggestion of the cell membrane remained. Replicas showed that this organism had a matted surface which was distorted under different conditions of lysis.

Bacteria↗