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D L Gutnick

Publications and source records attributed to D L Gutnick.

At least 37 records · Page 2Linked to original sources
PubMed1982

Emulsan production by Acinetobacter calcoaceticus in the presence of chloramphenicol.

When exponentially growing cultures of Acinetobacter calcoaceticus RAG-1 or RAG-92 were either treated with inhibitors of protein synthesis or starved for a required amino acid, there was a stimulation in the production of emulsan, an extracellular polyanionic emulsifier. Emulsan synthesis in the presence of chloramphenicol was dependent on utilizable sources of carbon and nitrogen and was inhibited by cyanide or azide or anaerobic conditions. Radioactive tracer experiments indicated that the enhanced production of emulsan after the addition of chloramphenicol was due to both the release of material synthesized before the addition of the antibiotic (40%) and de novo synthesis of the polymer (60%). Chemical analysis of RAG-1 cells demonstrated large amounts of polymeric amino sugars; it was estimated that cell-associated emulsan comprised about 15% of the dry weight of growing cells. The data are consistent with the hypothesis that a polymeric precursor of emulsan accumulates on the cell surface during the exponential growth phase; in the stationary phase or during inhibition of protein synthesis, the polymer is released as a potent emulsifier.

Acinetobacter↗
PubMed1981

Adherence of Acinetobacter calcoaceticus RAG-1 to human epithelial cells and to hexadecane.

The ability of Acinetobacter calcoaceticus RAG-1 to adhere to human epithelial cells was investigated and compared with its ability to adhere to a test hydrocarbon (hexadecane). RAG-1, a microorganism originally isolated for growth on hydrocarbon, adhered to epithelial cells when grown under conditions which promote its adherence to hexadecane; similarly, RAG-1 cells adhered poorly to epithelial cells when grown under conditions which cause the cells to possess low affinity towards hexadecane. A mutant derived from RAG-1, MR-481, deficient in its ability to adhere to hydrocarbon, was similarly unable to adhere to epithelial cells. RAG-1 adherence to epithelial cells was not blocked by a number of sugars tested. Streptococcus pyogenes, whose adherence to epithelial cells has been previously attributed to hydrophobic interactions, was also able to adhere to hexadecane. Results suggest that hydrophobic interactions mediate adherence of the strains studied to both epithelial cells and hydrocarbon.

Acinetobacter↗
PubMed1979

Emulsifier of Arthrobacter RAG-1: isolation and emulsifying properties.

The oil-degrading Arthrobacter sp. RAG-1 produced an extracellular nondialyzable emulsifying agent when grown on hexadecane, ethanol, or acetate medium. The emulsifier was prepared by two procedures: (i) heptane extraction of the cell-free culture medium and (ii) precipitation with ammonium sulfate. A convenient assay was developed for measurement of emulsifier concentrations between 3 and 75 micrograms/ml. The rate of emulsion fromation was proportional to both hydrocarbon and emulsifier concentrations. Above pH 6, activity was dependent upon divalent cations; half-maximum activity was obtained in the presence of 1.5 mM Mg2+. With a ratio of gas oil to emulsifier of 50, stable emulsions were formed with average droplet sizes of less than 1 micron. Emulsifier production was parallel to growth on either hydrocarbon or nonhydrocarbon substrates during the exponential phase; however, production continued after growth ceased.

Arthrobacter↗
PubMed1979

Emulsifier of Arthrobacter RAG-1: specificity of hydrocarbon substrate.

The purified extracellular emulsifying factor produced by Arthrobacter RAG-1 (EF-RAG) emulsified light petroleum oil, diesel oil, and a variety of crude oils and gas oils. Although kerosine and gasoline were emulsified poorly by EF-RAG, they were converted into good substrates for emulsification by addition of aromatic compounds, such as 2-methylnaphthalene. Neither aromatic nor aliphatic fractions of crude oil were emulsified by EF-RAG; however, mixtures containing both fractions were emulsified. Pure aliphatic or aromatic hydrocarbons were emulsified poorly by EF-RAG. Binary mixtures containing an aliphatic and an aromatic hydrocarbon, however, were excellent substrates for EF-RAG-induced emulsification. Of a variety of alkylcyclohexane and alkylbenzene derivatives tested, only hexyl- or heptylbenzene and octyl- or decylcyclohexane were effectively emulsified by EF-RAG. These data indicate that for EF-RAG to induce emulsification of hydrocarbons in water, the hydrocarbon substrate must contain both aliphatic and cyclic components. With binary mixtures of methylnaphthalene and hexadecane, maximum emulsion was obtained with 25% hexadecane.

Arthrobacter↗
PubMed1979

Emulsifier of Arthrobacter RAG-1: chemical and physical properties.

The extracellular emulsifier of Arthrobacter RAG-1 was deproteinized by hot phenol treatment and purified by fractional precipitation with (NH(4))(2)SO(4). The active fraction, precipitating between 30 and 35% saturation [EF-RAG(UET) WA], appeared to be homogeneous by immunodiffusion and sedimentation analysis. EF-RAG(UET) WA had an intrinsic viscosity of 750 cm(3)/g, a sedimentation constant of 6.06S, a diffusion constant of 5.25 x 10(-8) cm(2) s(-1), and a partial molar volume of 0.712 cm(3) g(-1). From these data a weight average molecular weight of 9.76 x 10(5) and a viscosity average molecular weight of 9.88 x 10(5) were calculated. EF-RAG(UET)WA contained 46.7% C, 7.01% H, and 6.06% N. Titration of the nonreducing polymer gave a single inflection point (pK' = 3.05), corresponding to 1.5 mumol of carboxyl groups per mg. Direct estimation of O-ester and hexose content of the highly acidic polymer yielded 0.65 and 0.29 mumol/mg, respectively. Mild alkaline hydrolysis released fatty acids with an average molecular weight of about 231. Strong acid hydrolysis of EF-RAG(UET)WA yielded d-glucose (minor), d-galactosamine (major), and an unidentified amino uronic acid (major).

Arthrobacter↗
PubMed1975

Differentiation between mutants of Escherichia coli K defective in oxidative phosphorylation.

Hybrid membrane particles from two mutants of Escherichia coli K12, Bv4 and K11, defective in oxidative phosphorylation, have been prepared, in which ATP-driven membrane energization is restored. A soluble factor of mutant K11 was found to have properties similar to parental crude coupling factor, ATPase (EC 3.6.1.3). Membrane particles of this mutant could not be reconstituted by parental coupling factor. Either parental coupling factor, or the soluble factor of mutant K11 could reconstitute both respiration-driven and ATP-driven energization to membrane particles of mutant Bv14 or to parental particles depleted of ATPase. Mutant Bv4 was found to be devoid of coupoing factor activity, while retaining the ability to hydrolyze ATP. Both mutants possess an ATPase with an altered binding to the membrane. Mutant K11 is impaired in respiration-driven amino acid transport, in contrast to mutant Bv4. The three major subunits of parental Escherichia coli ATPase have been isolated and antibodies have been prepared against these subunits. Antibodies against the largest subunit (alpha component) or against the intact catalytic subunits (alpha + beta components) inhibit both ATP-Pi exchange in the parent organism as well as ATP hydrolytic activity in parent and mutants. Antibodies against the two other subunits (beta or gamma components) also inhibit these two reactions, but were found to be less effective. Mutant N144, which lacks ATPase activity, shows no precipitin lines with anti-alpha, anti-beta, anti-gamma, or anti (alpha + beta) preparations. In contrast, mutants Bv4 and K11, exhibit cross-reactivity with all of the antisera.

Acridines↗
PubMed1975

Physiological suppression of a transport defect in Escherichia coli mutants deficient in Ca2+, Mg2+-stimulated adenosine triphosphatase.

Transport properties of membrane vesicles isolated from two adenosine triphosphatase-deficient mutants of Escherichia coli, NR70 and DL54, were compared with those of vesicles prepared from the corresponding parental strains. As reported previously (Rosen, 1973; Altendorf et al., 1974), vesicles prepared from these mutants grown under aerobic conditions exhibited defective amino acid transport, and activity was restored after treatment with dicyclohexylcarbodiimide. In sharp contrast, however, vesicles isolated from the same mutants grown anaerobically in the presence of nitrate exhibited completely normal transport activity when assayed under either anaerobic or aerobic conditions. Suppression of the transport defect was not due to the manner by which the vesicles were prepared, and the adenosine triphosphatase deficiency was not ameliorated by anaerobic growth in the presence of nitrite. Finally, the transport activity of vesicles prepared from the mutants grown under aerobic conditions was relatively resistant to the effect of 1.0 M guanidine hydrochloride extraction, whereas the activity of vesicles prepared from mutants grown anaerobically was totally refractory to the effect of the chaotrope.

Adenosine Triphosphatases↗
PubMed1974

Purification and properties of Mg2+-Ca2+ adenosinetriphosphatase from Escherichia coli.

A procedure for the purification of Mg(2+)-Ca(2+) adenosinetriphosphatase (EC 3.6.1.3) from E. coli, yielding relatively large amounts of highly active enzyme, is described. The enzyme consists of four nonidentical subunits. Trypsin treatment of purified enzyme yields a preparation consisting exclusively of the two larger subunits, which are sufficient for ATPase activity. Purified enzyme is inhibited by 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole; this inhibition is reversed by dithiothreitol, and the diazole is found preferentially associated with the beta-subunit of the enzyme. Antibody prepared against the trypsin-treated enzyme inhibited various ATP-dependent reactions as well as membrane-bound ATPase itself.

Adenosine Diphosphate↗