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PubMed1983

The absence of quinoprotein alcohol dehydrogenase in Acinetobacter calcoaceticus.

It is shown that the unusual NAD(P)+-independent quinoprotein alcohol dehydrogenase, said previously to be responsible for oxidation of ethanol during growth of Acinetobacter calcoaceticus LMD 79.39, was in fact isolated from an unidentified organism which contained cytochrome c and which has now been lost. Several genuine strains of A. calcoaceticus do not contain cytochrome c nor do they contain a quinoprotein alcohol dehydrogenase. The enzyme responsible for ethanol oxidation in these bacteria is an inducible NAD+-linked alcohol dehydrogenase.

Acinetobacter↗
PubMed1983

Immunochemical identification of the major cell surface agglutinogen of Acinetobacter calcoaceticus RAG-92.

The immunochemical and immunocytochemical characteristics of three Acinetobacter calcoaceticus RAG strains were compared in order to clarify the relationship between antibody-induced agglutination and the production of polyanionic extracellular emulsifier (termed emulsan). In addition to the parent, RAG-92, two mutant strains were examined: (1) a non-agglutinating emulsan-producer (AB15), and (2) an agglutinating mutant (16TLU) defective in the production of emulsan. A combined genetic-immunochemical approach was employed. This included the comparison of crossed immunoelectrophoresis patterns of parent and mutant supernates and the effect of absorption of anti-whole cell antiserum with mutant cells. In addition, agglutinability and competition studies were performed as well as electron microscopic cytochemistry. The results demonstrated that three major antigenic components were associated with the cell surface and the supernate. Mutant cells were altered both in their cell surface properties and in their extracellular products. One antigenic component, termed component C3, was the major cell surface agglutinogen; this component was absent in non-agglutinating mutants. Component C3 may be identical with or attached to the 300 nm projections on the parent cell surface, but it is not directly related to the presence of emulsan. It appears that emulsan plays little or no role in the phenomenon of antibody-induced agglutination of this organism.

Acinetobacter↗
PubMed1983

Regulation of expression of novel mandelate dehydrogenases in mutants of Acinetobacter calcoaceticus.

Wild-type strains of Acinetobacter calcoaceticus able to grow on only L(+)- or D(-)-mandelate gave rise to mutants that could grow on the other isomer of mandelate. Each mutant contained an additional mandelate dehydrogenase which was not expressed in the parent strain. The novel enzymes were shown to be controlled co-ordinately with the pre-existing enzymes for the conversion of mandelate into benzoate when induced with phenylglyoxylate, gratuitously induced with thiophenoxyacetate, subjected to anti-induction by 2-phenylpropionate or catabolite-repressed by succinate. Mutants which had been selected on the basis of possession of a constitutive phenylglyoxylate decarboxylase also constitutively expressed both the original and the novel mandelate dehydrogenases.

Acinetobacter↗
PubMed1984

Isolation, characterization and mapping of mandelate pathway mutants of Acinetobacter calcoaceticus.

Mutants of Acinetobacter calcoaceticus EBF 65/65 that could not grow on intermediates of the mandelate or benzyl alcohol pathways were isolated and in some cases the enzymic lesions were identified. Several catabolic markers were mapped using the plasmid pAV1. The mandelate genes appeared to be clustered near the auxotrophic marker phe-1 but were not all contiguous with each other. The gene responsible for the appearance of the novel L(+)-mandelate dehydrogenase appeared to be close to a gene responsible for the activity of the original D(-)-mandelate dehydrogenase.

Acinetobacter↗
PubMed1985

Plasmid transfer and behaviour in Acinetobacter calcoaceticus EBF65/65.

At least one plasmid from each of the incompatibility groups B, C, FIV, H2/S, I alpha, I delta, P, W and X was shown to be capable of transfer from Escherichia coli K12 to Acinetobacter calcoaceticus EBF65/65. Transfer was influenced by the presence of pAV2 (thought to encode a restriction-modification system) in the recipient strain; however, not all plasmids belonging to a particular incompatibility group behaved identically. All plasmids were unstable to varying degrees in A. calcoaceticus EBF65/65, but under suitable conditions were capable of transfer to further strains of EBF65/65 and re-transfer to E. coli K12. Of 40 recently isolated trimethoprim R plasmids 31 transferred successfully from E. coli K12 to A. calcoaceticus EBF65/65, but 17 of these 31 required the introduction of a second mobilizing plasmid for re-transfer to occur.

Acinetobacter↗
PubMed1986

The oxidation of glucose by Acinetobacter calcoaceticus: interaction of the quinoprotein glucose dehydrogenase with the electron transport chain.

The coupling of the quinoprotein glucose dehydrogenase to the electron transport chain has been investigated in Acinetobacter calcoaceticus. No evidence was obtained to support a previous suggestion that the soluble form of the dehydrogenase and the soluble cytochrome b associated with it are involved in the oxidation of glucose. Analysis of cytochrome content, and of reduction of cytochromes in membranes by substrates, and of sensitivity to cyanide indicated that glucose, succinate and NADH are all oxidized by way of the same b-type cytochrome(s) and cytochrome oxidases (cytochrome o and cytochrome d). Mixed inhibition studies [with KCN and hydroxyquinoline N-oxide (HQNO)] showed that the b-type cytochrome(s) formed a binary complex with the o-type oxidase and that there was thus no communication between the electron transport chains at the cytochrome level. Measurements of the reduction of ubiquinone-9 by glucose and NADH, and inhibitor studies using HQNO, indicated that the ubiquinone mediates electron transport from both the glucose and NADH dehydrogenases. In some conditions the quinone pool facilitated communication between the 'glucose oxidase' and 'NADH oxidase' electron transport chains, but in normal conditions these chains were kinetically distinct.

Acinetobacter↗
PubMed1986

Prophage induction by ultraviolet light in Acinetobacter calcoaceticus.

UV-induction of prophage P78 of Acinetobacter calcoaceticus increased with the UV-dose given to the lysogenic strain from the spontaneous induction frequency of about 0.8% to a maximal frequency of 10%. This 10- to 20-fold increase of induction frequency, as measured by the number of infective centres, was accompanied by a 1000-fold increase in the yield of free phage. This effect was probably due to an increase in burst size under the conditions of lysogenic induction. Unusually, the lysogen was more resistant to UV-irradiation than the corresponding non-lysogenic strain.

Acinetobacter↗
PubMed1988

Occurrence, transfer and mobilization in epilithic strains of Acinetobacter of mercury-resistance plasmids capable of transformation.

A 7.8 kb plasmid (pQM17) encoding mercury resistance was isolated from two epilithic strains of Acinetobacter calcoaceticus. The plasmid had a broad host range when mobilized by RP1, transferring into Pseudomonas aeruginosa, P. putida, P. fluorescens, Escherichia coli, Proteus vulgaris and Chromobacterium sp. with frequencies ranging from 5.3 x 10(-9) to 4.6 x 10(-4) per recipient. The plasmid could be transferred into A. calcoaceticus BD413 using intact cells of donor and recipient bacteria (i.e. natural transformation) and there was a broad temperature optimum (14-37 degrees C) for transformation. Transformation was as efficient in liquid matings as on plates but there was no effect of pH in the range 5.6-7.9. Maximum transformation frequencies were obtained after 24 h on agar plates containing 3.5-10 g C 1-1 with donor to recipient ratios ranging from 6 to 415.

Acinetobacter↗
PubMed1988

Comparison of mandelate dehydrogenases from various strains of Acinetobacter calcoaceticus: similarity of natural and 'evolved' forms.

In previous work it had been shown that Acinetobacter calcoaceticus wild-type strain NCIB 8250 had only an L-mandelate deydrogenase but it could give rise to mutants that contained an evolved D-mandelate dehydrogenase; conversely, wild-type strain EBF 65/65 had only a D-mandelate dehydrogenase but gave rise to mutants that possessed an evolved L-mandelate dehydrogenase. Several other wild-type strains of A. calcoaceticus have now been shown to grow on both enantiomers of mandelate. In every case the L-mandelate dehydrogenases were found to be much more heat-stable and insensitive to inhibition by p-chloromercuribenzoate than were the D-mandelate dehydrogenases when measured in bacterial extracts. All the D-mandelate dehydrogenases in the wild-type strains were inactivated to about the same extent by an antiserum that had been raised in a rabbit against an evolved D-mandelate dehydrogenase. An evolved D-mandelate deydrogenase (from a mutant strain derived from strain NCIB 8250) and an original D-mandelate dehydrogenase (from a mutant strain derived from strain EBF 65/65) were purified to homogeneity by the same procedure and were indistinguishable as judged by immunological cross-reactivity of the native and the sodium-dodecyl-sulphate-denatured enzymes, solubility in cholate, net charge at pH 7.5, pI value, salting-out properties, Mr value, apparent K(m) value for D-mandelate, heat-stability and sensitivity to p-chloromercuribenzoate. The most likely explanation for the appearance of evolved mandelate dehydrogenases in strains of A. calcoaceticus is that cryptic genes become expressed.

Acinetobacter↗
PubMed1988

Effect of hexadecane-induced vesiculation on the outer membrane of Acinetobacter calcoaceticus.

Lipopolysaccharide-rich vesicles were released from Acinetobacter calcoaceticus 69V during growth on hexadecane. Vesicle formation occurred over the whole surface of the cell as demonstrated by scanning electron microscopy. In contrast, the surface of acetate-grown cells, for which little lipopolysaccharide was found in the growth medium, appeared smooth. The overall chemical composition as well as the protein and phospholipid composition of the outer membranes of both cell types was very similar. In the vesicles all outer membrane proteins were found with the exception of an Mr 10,000 polypeptide corresponding to Braun's lipoprotein. Compared with the outer membrane, the vesicles contained more phosphatidylethanolamine. Hexadecane-grown cells were susceptible to exogenously added phospholipase. Nevertheless the barrier function towards lysozyme was retained.

Acinetobacter↗
PubMed1992

Purification and characterization of an extracellular beta-lactamase produced by Acinetobacter calcoaceticus.

A beta-lactamase was purified 430-fold from the culture supernatant of Acinetobacter calcoaceticus by ion exchange chromatography on CM-Sephadex and affinity chromatography on phenylboronic-acid-agarose. The purified enzyme was homogeneous as judged by SDS-PAGE, and was characterized with respect to molecular mass (38 and 41 kDa by gel filtration on Sephadex G-75 and SDS-PAGE, respectively), pH optimum (pH 7.0), temperature optimum (45 degrees C) and isoelectric point (9.3). The beta-lactamase showed mainly cephalosporinase activity. It was inhibited by cloxacillin, carbenicillin, penicillanic acid sulphone (sulbactam) and aztreonam. It was not inhibited by clavulanic acid up to a concentration of 0.25 mM. Neither EDTA nor p-chlormercuribenzoate, up to concentrations of 1 or 100 mM, respectively, affected activity. According to these characteristics, it is a typical CEP-N cephalosporinase.

Acinetobacter calcoaceticus↗
PubMed1992

Purification and characterization of L-2,4-diaminobutyrate decarboxylase from Acinetobacter calcoaceticus.

Acinetobacter calcoaceticus ATCC 23055 produces a large amount of 1,3-diaminopropane under normal growth conditions. The enzyme responsible, L-2,4-diaminobutyrate (DABA) decarboxylase (EC 4.1.1.-), was purified to electrophoretic homogeneity from this bacterium. The native enzyme had an M(r) of approximately 108,000, with a pI of 5.0, and was a dimer composed of identical or nearly identical subunits with apparent M(r) 53,000. The enzyme showed hyperbolic kinetics with a Km of 1.59 mM for DABA and 14.6 microM for pyridoxal 5'-phosphate as a coenzyme. The pH optimum was in the range 8.5-8.75, and Ca2+ gave a much higher enzyme activity than Mg2+ as a cationic cofactor. N-gamma-Acetyl-DABA, 2,3-diaminopropionic acid, ornithine and lysine were inert as substrates. The enzyme was different in subunit structure, N-terminal amino acid sequence and immunoreactivity from the DABA decarboxylase of Vibrio alginolyticus previously described.

Acinetobacter calcoaceticus↗
PubMed1992

Long-chain alcohol and aldehyde dehydrogenase activities in Acinetobacter calcoaceticus strain HO1-N.

Three alcohol dehydrogenases have been identified in Acinetobacter calcoaceticus sp. strain HO1-N: an NAD(+)-dependent enzyme and two NADP(+)-dependent enzymes. One of the NADP(+)-dependent alcohol dehydrogenases was partially purified and was specific for long-chain substrates. With tetradecanol as substrate an apparent Km value of 5.2 microM was calculated. This enzyme has a pI of 4.5 and a molecular mass of 144 kDa. All three alcohol dehydrogenases were constitutively expressed. Three aldehyde dehydrogenases were also identified: an NAD(+)-dependent enzyme, an NADP(+)-dependent enzyme and one which was nucleotide independent. The NAD(+)-dependent enzyme represented only 2% of the total activity and was not studied further. The NADP(+)-dependent enzyme was strongly induced by growth of cells on alkanes and was associated with hydrocarbon vesicles. With tetradecanal as substrate an apparent Km value of 0.2 microM was calculated. The nucleotide-independent aldehyde dehydrogenase could use either Würster's Blue or phenazine methosulphate (PMS) as an artificial electron acceptor. This enzyme represents approximately 80% of the total long-chain aldehyde oxidizing activity within the cell when the enzymes were induced by growing the cells on hexadecane. It is particulate but can be solubilized using Triton X-100. The enzyme has an apparent Km of 0.36 mM for decanal.

Acinetobacter calcoaceticus↗
PubMed1993

Growth-phase-dependent expression of the lipolytic system of Acinetobacter calcoaceticus BD413: cloning of a gene encoding one of the esterases.

Acinetobacter calcoaceticus BD413, when grown in batch culture in nutrient broth, produces both extracellular lipase activity and cell-bound esterase activity during and after the transition between exponential growth and the stationary phase. From a library of A. calcoaceticus DNA in Escherichia coli, plasmids were isolated that enabled E. coli to grow on media with tributyrin as the sole carbon source. Assays with model substrates classified the product of the cloned gene as an esterase. Via deletion analysis, the esterase gene was mapped on a 1.8 kbp chromosomal DNA fragment. This fragment was sequenced and found to contain one open reading frame, termed estA, which encodes a protein of 40.0 kDa. The amino acid sequence of this protein shows homology to a number of lipolytic enzymes, most notably to esterases. Deletion of estA only partially abolished cell-bound esterase activity in A. calcoaceticus, indicating that BD413 forms at least two esterases. Both esterases show the same temporal regulation of expression. beta-Galactosidase activity was measured in strains in which a promoterless lacZ gene was inserted into estA. Induction of lacZ expression in these strains also occurred at the end of exponential growth in batch cultures, indicating that production of the esterase is regulated at the genetic level.

Acinetobacter calcoaceticus↗
PubMed1996

The expression of the Acinetobacter calcoaceticus recA gene increases in response to DNA damage independently of RecA and of development of competence for natural transformation.

Using the lacZ operon fusion technique, the transcriptional control of the Acinetobacter calcoaceticus recA gene was studied. A low (approximately twofold) inductive capacity was observed for compounds that damage DNA and/or inhibit DNA replication, e.g. methyl methanesulfonate, mitomycin C, UV light and nalidixic acid. Induction of the recA gene by DNA damage was independent of functional RecA. The presence of the recA promoter region on a multicopy plasmid had the same effect on recA transcription as the presence of DNA-damaging agents. Thus, recA expression in A. calcoaceticus appears to be regulated in a novel fashion, possibly involving a non-LexA-like repressor. Regulation of the recA gene in A. calcoaceticus appears not to be part of a regulon responsible for competence for natural transformation: in cells exhibiting extremely low transformation frequencies, the level of transcription of the recA gene was found to be comparable to the level found in cells in the state of maximal competence.

Acinetobacter calcoaceticus↗
PubMed1997

Plasmid-encoded genes specifying aniline oxidation from Acinetobacter sp. strain YAA.

Acinetobacter sp. strain YAA is able to use aniline and o-toluidine as the sole carbon and energy source. This strain has several different plasmids and acridine orange curing suggested that aniline utilization in strain YAA was plasmid-encoded. The gene cluster involved in aniline oxidation was cloned in Escherichia coli JM109 from the total plasmid DNA of strain YAA. A recombinant E. coli containing an 18.5 kb insert fragment showed yellow colouration on aniline-containing plates, indicating the formation of 2-hydroxymuconic semialdehyde from aniline. In addition, subcloning of a 9.0 kb SalI fragment from the insert in E. coli resulted in the accumulation of catechol. Southern hybridization studies indicated that the aniline oxygenase gene (atdA) was present on one of the plasmids, pYA1. These results suggest that in strain YAA aniline is degraded via catechol through a pathway involving meta-cleavage of the benzene-ring by plasmid-encoded genes including atdA.

Acinetobacter↗
PubMed1999

Regulation of polyphosphate kinase gene expression in Acinetobacter baumannii 252.

A strain of Acinetobacter baumannii cultured in butyric acid media was found to take up phosphate following a period of phosphate release. PCR was used to clone the polyphosphate kinase (ppk) gene from the strain. The promoter for the ppk gene was functional in the heterologous Escherichia coli host. Using RT-PCR, transcription of the ppk gene was found to be regulated by phosphate concentration.

5' Untranslated Regions↗
PubMed2001

Analysis of the wee gene cluster responsible for the biosynthesis of the polymeric bioemulsifier from the oil-degrading strain Acinetobacter lwoffii RAG-1.

A cluster (27 kbp) of genes responsible for the biosynthesis of the amphipathic, polysaccharide bioemulsifier emulsan from the oil-degrading Acinetobacter lwoffii RAG-1 was isolated and characterized. The complete sequence of this cluster, termed wee, consisted of 20 ORFs. One set of 17 ORFs was transcribed in one direction, while a second set of three ORFs, 607 bp upstream of the first, was transcribed in the opposite direction. Mutations in either of the two regions caused defects in emulsan production, yielding specific activities of 5-14% of parental emulsifying activity. Putative functions could be assigned to proteins involved in production of nucleotide amino sugar precursors, transglycosylation, transacetylation, polymerization and transport. However, no JUMPstart or ops sequences, normally found associated with some polysaccharide biosynthetic gene clusters, were identified. Evidence is presented suggesting that the bioemulsifier may be a member of the group 1 or group 4 polysaccharides.

Acinetobacter↗