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PubMed1975

Influence of colloidal iron on the respiration of a species of the genus Acinetobacter.

Washed suspensions of Acinetobacter sp. isolated from water caused the precipitation of iron from a suspension of colloidal ferric iron at pH 6.0 and 7.6. Iron-encrusted cells of the bacterium formed large aggregates. The amount of iron removed from the colloidal preparation in the form of aggregates was from 21 to 52% at pH 7.6 and 49% an pH 6.0 by the bacterial cells. Endogenous respiration rates of the iron-encrusted cells were from 32 to 72% lower than the rates for unencrusted cells. Respiration rates, measured polarographically in the presence of glucose, were also greatly reduced by the coating of iron on the cells.

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↗
PubMed1986

Plasmid RP1-mediated susceptibility of Acinetobacter calcoaceticus to rat polymorphonuclear leukocyte granule contents.

The resistance plasmid RP1 was transferred by conjugation to a plasmidless strain of Acinetobacter calcoaceticus. Acquisition and expression of RP1 by A. calcoaceticus HO1-N was associated with an increase in sensitivity to the antimicrobial activity of extracted contents from rat polymorphonuclear leukocyte granules. Plasmid RP1-associated antibiotic resistance and sensitivity to granule contents were cured by exposure to acridine orange. Assays with granule extract fractions separated by fast protein liquid chromatography showed myeloperoxidase, protease, and lysozyme fractions to possess little or no antimicrobial activity against the A. calcoaceticus strains. A protein fraction designated peak D, containing two low-molecular-weight cationic peptides (M. J. Loeffelholz and M. C. Modrzakowski, Anal. Biochem., in press), did possess antimicrobial activity against both HO1-N and Ho1-N(RP1) strains, with the HO1-N(RP1) strain being significantly more sensitive.

Acinetobacter↗
PubMed1987

Outer membrane permeability of Acinetobacter calcoaceticus mediates susceptibility to rat polymorphonuclear leukocyte granule contents.

Growth of Acinetobacter calcoaceticus on specific alkanes altered the outer membrane permeability of the organism, as indicated by a change in sensitivity to the antibiotic actinomycin D. As the carbon length of the alkane energy source decreased, outer membrane permeability and susceptibility to actinomycin D increased. Concomitant with the increase in outer membrane permeability, A. calcoaceticus became more susceptible to the oxygen-independent antimicrobial activity of extracted contents from rat polymorphonuclear leukocyte granules. Individual fractions of granule extract possessed no antimicrobial activity against A. calcoaceticus. The alkane-induced change in outer membrane permeability was not associated with alterations of lipopolysaccharide O antigen. An outer membrane permeability mechanism, independent of changes in lipopolysaccharide content, mediating susceptibility to the oxygen-independent antimicrobial activity of rat polymorphonuclear leukocyte granule contents is suggested.

Acinetobacter↗
PubMed1988

Antimicrobial mechanisms against Acinetobacter calcoaceticus of rat polymorphonuclear leukocyte granule extract.

The antimicrobial mechanisms of rat polymorphonuclear leukocyte granule extract and isolated extract fractions against Acinetobacter calcoaceticus were examined. Crude granule extract and a fraction containing low-molecular-weight cationic peptides (peak D) reduced the viability of A. calcoaceticus and inhibited the uptake of radiolabeled macromolecule precursors by cells. The inhibitory activity observed with peak D was not as great as that of crude granule extract containing equivalent amounts of peak D protein. Crude extract also inhibited incorporation of uracil into trichloroacetic acid-precipitable material, while no isolated fraction, including peak D, had any substantial effect on incorporation. The antimicrobial activities of crude granule extract were more sensitive to boiling than those of isolated peak D. Preincubation of A. calcoaceticus with either crude granule extract or a fraction (peak B) possessing proteolytic activity but lacking any antimicrobial activity caused cells to become sensitive to a subinhibitory concentration of actinomycin D, suggesting that granule extract and peak B increase the outer membrane permeability of A. calcoaceticus. The antimicrobial granule extract fraction, peak D, did not affect outer membrane permeability. These results suggest that rat polymorphonuclear leukocyte granule extract reduces the viability of A. calcoaceticus by inhibiting the transport and incorporation of macromolecule precursors and that either whole granule extract is required for complete antimicrobial activity or an unidentified component is responsible for antimicrobial activity in addition to peak D. The granule extract activity that increases outer membrane permeability does not appear to be directly responsible for the observed decrease in viability.

Acinetobacter↗
PubMed1999

Autoantibodies to brain components and antibodies to Acinetobacter calcoaceticus are present in bovine spongiform encephalopathy.

Bovine spongiform encephalopathy (BSE) is a neurological disorder, predominantly of British cattle, which belongs to the group of transmissible spongiform encephalopathies together with Creutzfeldt-Jakob disease (CJD), kuru, and scrapie. Autoantibodies to brain neurofilaments have been previously described in patients with CJD and kuru and in sheep affected by scrapie. Spongiform-like changes have also been observed in chronic experimental allergic encephalomyelitis, at least in rabbits and guinea pigs, and in these conditions autoantibodies to myelin occur. We report here that animals with BSE have elevated levels of immunoglobulin A autoantibodies to brain components, i.e., neurofilaments (P < 0.001) and myelin (P < 0.001), as well as to Acinetobacter calcoaceticus (P < 0.001), saprophytic microbes found in soil which have sequences cross-reacting with bovine neurofilaments and myelin, but there were no antibody elevations against Agrobacterium tumefaciens or Escherichia coli. The relevance of such mucosal autoantibodies or antibacterial antibodies to the pathology of BSE and its possible link to prions requires further evaluation.

Acinetobacter calcoaceticus↗
PubMed2002

Gastritis and hypergastrinemia due to Acinetobacter lwoffii in mice.

In mouse models and humans, Helicobacter pylori is associated with an increase in serum gastrin and gastrin-expressing (G) cells with a concomitant decrease in somatostatin-expressing D cells. Inflammation of the gastric mucosa can progress to metaplastic changes in the stomach and to decreased colonization by H. pylori and increased colonization by non-H. pylori organisms. In addition, about 20% of individuals with chronic gastritis are H. pylori negative, suggesting that other organisms may induce gastritis. Consistent with this hypothesis, we report here that Acinetobacter lwoffii causes the same histologic changes as does H. pylori. Gastric epithelial cells were isolated from the entire stomach by an enzymatic method for quantitation by both flow cytometry and morphometric analysis. Two months after mice were inoculated with H. pylori or A. lwoffii, the mucosal T- and B-cell numbers significantly increased. After 4 months of infection, there was a threefold increase in the number of G cells and a doubling in the number of parietal cells. A threefold decrease in the number of D cells occurred in H. pylori- and A. lwoffii-infected mice. Plasma gastrin levels increased after both H. pylori and A. lwoffii infection. Histology revealed the presence of inflammation in the gastric mucosa with both A. lwoffii and H. pylori infection. A periodic acid-Schiff stain-alcian blue stain revealed mucous gland metaplasia of the corpus. Collectively, the results demonstrate that gastritis and hypergastrinemia are not specific for H. pylori but can be induced by other gram-negative bacteria capable of infecting the mouse stomach.

Acinetobacter Infections↗
PubMed2006

Rapid evolution of diminished transformability in Acinetobacter baylyi.

The reason for genetic exchange remains a crucial question in evolutionary biology. Acinetobacter baylyi strain ADP1 is a highly competent and recombinogenic bacterium. We compared the parallel evolution of wild-type and engineered noncompetent lineages of A. baylyi in the laboratory. If transformability were to result in an evolutionary benefit, it was expected that competent lineages would adapt more rapidly than noncompetent lineages. Instead, regardless of competency, lineages adapted to the same extent under several laboratory conditions. Furthermore, competent lineages repeatedly evolved a much lower level of transformability. The loss of competency may be due to a selective advantage or the irreversible transfer of loss-of-function alleles of genes required for transformation within the competent population.

Acinetobacter↗
PubMed1974

Purification and properties of 4-hydroxy-2-ketopimelate aldolase from Acinetobacter.

The chemical synthesis of 4-hydroxy-2-ketopimelic acid is described. An aldolase that cleaves this compound to succinic semialdehyde and pyruvate has been purified from Acinetobacter grown at the expense of 4-hydroxyphenylacetic acid. The molecular weight of the enzyme was about 158,000 from sedimentation equilibrium data; other physical determinations gave values in reasonable agreement. The protein was globular and was dissociated in sodium dodecyl sulfate to give a species of molecular weight 25,700. The enzyme attacked both enantiomers of synthetic 4-hydroxy-2-ketopimelate and was stimulated by Mg(2+) and Mn(2+) ions.

Acinetobacter↗
PubMed1976

Preparations and properties of ribonucleic acid polymerase from Acinetobacter calcoaceticus.

Deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase (EC 2.7.7.6) from Acinetobacter calcoaceticus was purified to apparent homogeneity and its properties were compared with those of the Escherichia coli B enzyme. The molecular weights of the two native active enzymes as well as their alpha and beta subunits appeared to be similar. No subunit corresponding to that of sigma from E. coli was found, and furthermore no separation between the beta subunits could be detected by gel electrophoresis. A number of different DNAs were transcribed by the enzyme from A. calcoaceticus. Maximal RNA synthesis occurred at pH 8.7, 10 mM Mg2+, or 0.3 mM Mn2+ and at a total ionic strength of 0.1. Higher ionic strengths led to increasing inhibition of transcription and at mu = 0.4 complete inhibition was observed. The mechanism of inhibition of salt was not related to the initiation event as observed with T4 core RNA polymerase (R.Kleppe, 1975). In an attempt to understand the mechanism of inhibition by salt, the effect of ionic strength on the sedimentation properties of the enzyme was investigated. At low ionic strength, enzyme species with sedimentation coefficients, s20,w, of 5.8S, 12.4S, and 19.3S were present. In buffers with higher ionic strengths the relative amounts of the 12.4S species decreased. It is suggested, therefore, that the inhibition of activity at higher salt concentrations is caused by a decrease in concentration of the active enzyme species.

Acinetobacter↗
PubMed1976

Regulation of enzyme synthesis in the tryptophan pathway of Acinetobacter calcoaceticus.

In Acinetobacter calcoaceticus the seven genes coding for the enzymes responsible for tryptophan synthesis map at three chromosomal locations. Two three-gene clusters, one (trpGDC) specifying the small subunit of anthranilate synthase, phosphoribosyl transferase, and indoleglycerol phosphate synthase and the other (trpFBA) specifying phosphoribosyl anthranilate isomerase and both tryptophan synthase subunits, are not linked to each other or to the trpE gene specifying the large anthranilate synthase subunit. When regulation of trp gene expression is studied in the wild type, only the level of the trpF gene product decreases upon addition of tryptophan to the medium. Tryptophan starvation of tryptophan auxotrophs, however, results in increased levels of all the tryptophan enzymes; this and additional evidence suggests that the expression of all the trp genes is subject to repression. The trpGDC genes are coordinately controlled, and the trpE gene is regulated in parallel with them. The trpFBA genes are controlled neither coordinately nor in parallel with the other trp genes, but respond proportionally when compared with each other. So far, two types of constitutive mutants have been found. The first class of mutants apparently occurs in the structural gene for a repressor protein; this repressor locus is unlinked to any of the biosynthetic trp genes and affects only the expression of trpE and the trpGDC cluster. The second class contains mutants closely linked to the trpGDC region; they overproduce only the gene products of this cluster.

Acinetobacter↗
PubMed1976

Synthesis and turnover of the regularly arranged surface protein of Acinetobacter sp. relative to the other components of the cell envelope.

The formation of the components of the cell envelope of Acinetobacter sp. 199A was investigated by measuring the incorporation of [3H]leucine into protein, [14C]galactose into lipopolysaccharide, 32P into phospholipid, and [3H]diaminopimelic acid into peptidoglycan. Whereas the lipopolysaccharide and intrinsic protein of the outer membrane were stable, some of the regularly arranged surface protein, the alpha-protein, was lost into the growth medium. Only newly synthesized alpha-protein was lost. The peptidoglycan of the murein layer was also labile. Selective inhibition of the formation of individual components of the cell envelope with penicillin, chloramphenicol, and bacitracin showed that incorporation of protein into the outer membrane required the simultaneous formation of complete lipopolysaccharide. The converse was not true: protein synthesis was not required for lipopolysaccharide incorporation. Formation of the outer membrane and the murein layer proceeded independently.

Acinetobacter↗
PubMed1976

Catechol 1,2-dioxygenase from Acinetobacter calcoaceticus: purification and properties.

Procedures for the purification of catechol 1,2-dioxygenase from extracts of Acinetobacter calcoaceticus strain ADP-96 are described. The purified enzyme was homogeneous as judged by ultracentrifugation and acrylamide gel electrophoresis. The enzyme contained 2 g-atoms of iron per mol of protein. The enzyme had a broad substrate specificity and catalyzed the oxidation of catechol, 4-methylcatechol, 3-methylcatechol, and 3-isopropyl catechol. The activity of the enzyme was inhibited by heavy metals, sulfhydryl inhibitors, and substrate analogues. The molecular weight of the enzyme was 85,000 as estimated by filtration on Bio-Gel agarose and 81,000 as estimated by sedimentation equilibrium analysis. The subunit size determined by sodium dodecyl sulfate-gel electrophoresis was 40,000. The amino terminal amino acid was methionine. The amino acid composition and spectral properties of 1,2-dioxygenase are also presented. Antisera prepared against the purified enzyme cross-reacted and inhibited enzyme activity in crude extracts from the other strain of A. calcoaceticus, but failed to cross-react and inhibit isofunctional enzyme from organisms of the genera Pseudomonas, Alcaligenes, and Nocardia.

Acinetobacter↗
PubMed1977

Characterization of lysocardiolipin from Acinetobacter sp. HO1-N.

Triacyl-lysocardiolipin (triacyl-LCL) and diacyl-LCL were isolated from Acinetobacter sp. HO1-N, and their structures were determined by chemical, physical, and enzymatic procedures. Deacylation of triacyl-LCL and diacyl-LCL yielded bis-glycerylphosphorylglycerol. Periodate oxidation of both lysolipids was negative. Diglyceride and 2-monoglyceride resulted from the acetic acid hydrolysis of triacyl-LCL, whereas 2-monoglyceride was the sole product obtained from diacyl-LCL. Cardiolipin (CL)-specific phospholipase D treatment of triacyl-LCL yielded lysophosphatidylglycerol and phosphatidic acid. Pancreatic lipase treatment of CL yielded triacyl-LCL and diacyl-LCL. 31P nuclear magnetic resonance spectrometry showed two resonance peaks separated by 40 HZ for CL, two overlapping peaks separated by 14 HZ for triacyl-LCL, and one peak for diacyl-LCL. The proportion of lysocardiolipin increased as a function of cell age, representing 2 to 3% of the total phospholipids in early- and mid-exponential growth, 5 to 7% in late-exponential growth, and 12% in the stationary growth phase.

Acinetobacter↗
PubMed1977

Outer membrane phospholipase A from Acinetobacter sp. HO1-N.

A phospholipase A1 activity that hydrolyzed cardiolipin to triacyl- and diacyl-lysocardiolipin was localized in outer membrane preparations derived from Acinetobacter sp. HO1-N. The specific activity of the enzyme derived from hexadecane-grown cells was 2.5 to 3 times higher than that derived from NBYE-grown cells. An apparent Km of 2.22 mM was determined, although inhibition kinetics resulted at the higher cardiolipin substrate concentrations. Optimal reaction conditions established on metal requirements. Enzyme activity was obligately dependent on Triton X-100 (0.5%) and was inhibited by cationic and anionic detergents. Cardiolipin-specific phospholipase D converted triacyl-lysocardiolipin to lysophosphatidylglycerol and phosphatidic acid. The specific activity of this enzyme was approximately 100 times greater than that reported for other membrane preparations derived from microorganisms.

Acinetobacter↗
PubMed1978

Utilization of oxalacetate by Acinetobacter calcoaceticus: evidence for coupling between malic enzyme and malic dehydrogenase.

Growth of Acinetobacter calcoaceticus strain BD413 in malate-mineral medium resulted in the excretion of large quantities of oxalacetate. Malate was virtually depleted by the time the cell density reached 60% of its final value; most of the remaining growth took place at the expense of oxalacetate. Experiments in which oxalacetate was used as the initial substrate showed that pyruvate was not utilized until most of the oxalacetate disappeared. The generation time for growth on malate or oxalacetate was approximately 40 min; the generation time for growth on pyruvate was 62 min, which implies that pyruvate transport may be rate limiting. Oxalacetate and pyruvate, however, supported approximately the same growth yield. These observations suggested that the first step in the utilization of oxalacetate as an energy source consisted of an enzymatic decarboxylation of the keto acid to pyruvate and CO(2). Three enzyme reactions that carry out this decarboxylation have been detected in extracts of A. calcoaceticus. The first, which functioned maximally at pH 4.8, was attributable to the oxalacetate decarboxylase activity of oxidized diphosphopyridine nucleotide-malic enzyme. The second and third, which functioned in the neutral pH range, resulted from coupling of oxidized diphosphopyridine nucleotide-malic enzyme to reduced diphosphopyridine nucleotide-dependent malic dehydrogenase, and oxidized triphosphopyridine nucleotide-malic enzyme to a reduced triphosphopyridine nucleotide-dependent malic dehydrogenase. The efficiency of these coupled reactions was high enough so that the overall reaction could be physiologically significant.

Acinetobacter↗