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PubMed1990

Characterisation of a siderophore from Acinetobacter calcoaceticus.

The Gram-negative bacterium Acinetobacter calcoaceticus was examined for production of siderophores and iron-repressible outer membrane proteins following growth in iron-restricted media. The iron chelator, 2,3-dihydroxybenzoic acid was identified in the culture supernatant by 1H nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). A group of outer membrane proteins between 80 and 85 kDa were induced under iron restriction.

Acinetobacter↗
PubMed1990

Polyphosphate production by strains of Acinetobacter.

Of four strains of Acinetobacter isolated from a pilot plant exhibiting enhanced biological phosphate removal from sewage, two strains (RA3116 and RA3117) accumulated more than 10 times the amount of polyphosphate accumulated by the other two strains (RA3114 and RA3123). Variants isolated from RA3116 and RA3117 showed polyphosphate levels similar to RA3114 and RA3123. No correlation was found between the polyphosphate content of the strains and levels of several enzymes that have been implicated in polyphosphate formation.

Acinetobacter↗
PubMed1989

Cloning and expression in Escherichia coli of an esterase-coding gene from the oil-degrading bacterium Acinetobacter calcoaceticus RAG-1.

A putative esterase gene (est) from Acinetobacter calcoaceticus RAG-1 has been cloned into Escherichia coli. Esterase-positive clones exhibited high levels of esterase activity even in intact cells. In addition, expression of the est gene conferred on E. coli the ability to grow on simple triglycerides such as triacetin (TAC). The original esterase-positive plasmid pRA17 carried a 2.2-kb insert from a partial MboI digest of RAG-1 DNA, which gave a single band with RAG-1 DNA following Southern hybridization. By subcloning and sequencing the est gene was found to contain a sequence of 870 bp which could be translated to yield a protein of Mr 32,700. In support of the sequencing results was the finding that when pRA17 was expressed in minicells, a unique peptide of Mr 32,500 was identified. This peptide was not found in minicells transformed with esterase-negative plasmids, such as pRA176, which contained a Tn5 insertion in the est gene. The fact that the production of active esterase depended on the orientation of the est gene within the vector suggested that transcription proceeded from the tet promoter in pBR322.

Acinetobacter↗
PubMed1990

Analysis and nucleotide sequence of an origin of DNA replication in Acinetobacter calcoaceticus and its use for Escherichia coli shuttle plasmids.

A shuttle plasmid for Acinetobacter calcoaceticus and Escherichia coli has been constructed from a cryptic A. calcoaceticus lwoffi plasmid and pBR322. It is transformed to A. calcoaceticus BD413 by natural competency, yielding about 10(6) transformants per microgram of plasmid DNA. The ApR and TcR genes of pBR322 are functional in A. calcoaceticus. A gene bank was constructed from chromosomal A. calcoaceticus DNA and the shuttle plasmid. Direct transformation to A. calcoaceticus yielded about 95% recombinants, indicating a sixfold enrichment of recombinant plasmids compared to E. coli. One clone complementing a trpE mutation carried a 20-kb insertion and transformed with a 30-fold higher efficiency when compared to the vector. A deletion analysis of the shuttle plasmid indicates that 2.2 kb is necessary for autonomous replication and stable maintenance in A. calcoaceticus. No rearrangements of the DNA or loss of plasmids are found in that organism, even in the absence of selective pressure, when this sequence is present. A further insertional inactivation analysis creating lacZ transcriptional fusions suggests that the origin of replication (ori) is contained within about 1350 bp. Analysis of beta-galactosidase production in A. calcoaceticus indicates that only a weak promoter activity is directed out of one end of this ori. Its sequence contains A + T-rich regions, an 18-bp element with nearly perfect palindromic symmetry and eleven repeats of the consensus sequence, AAAAAATAT, eight of which are clustered within 360 bp. However, no open reading frames or significant homologies to other ori were found.

Acinetobacter↗
PubMed1993

Evolutionary divergence of pobA, the structural gene encoding p-hydroxybenzoate hydroxylase in an Acinetobacter calcoaceticus strain well-suited for genetic analysis.

The pobA gene encoding p-hydroxybenzoate hydroxylase (PobA) from Acinetobacter calcoaceticus has been developed as a genetic tool for the analysis of structure-function relationships in this enzyme. By exploiting the favorable genetic system of A. calcoaceticus strain ADP1, it is possible both to select and to map mutations which disturb PobA activity; characterization and sequence determination of mutants derived in this manner may complement site-directed studies with the homologous Pseudomonas aeruginosa gene. We have determined the nucleotide (nt) sequence of A. calcoaceticus pobA and performed a systematic comparison of the deduced amino acid (aa) sequence with that of the PobA enzyme from Pseudomonas fluorescens, for which the three-dimensional structure is known. Despite a 26% difference in the G+C content of the homologous genes, constraints against structural divergence of the proteins were revealed by an overall identity of 62.4% in the aligned aa sequences of PobA. Clusters of identical sequence occur at previously identified sites of ligand binding and at regions associated with subunit-subunit interaction. Based on the conservation of specific residues involved in flavin binding, we have assembled a consensus sequence for nicotinamide-flavoprotein monooxygenases which differs from that of the oxidoreductase class of flavoproteins. In addition to the conserved regions shared by the two PobA homologs, there are isolated pockets of divergence. The nt sequence divergence in one such region within the A. calcoaceticus gene can be attributed to the acquisition of short nt sequence repetitions.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1995

Nucleotide sequences transferred by gene conversion in the bacterium Acinetobacter calcoaceticus.

Exchange of nucleotide (nt) sequences between the catIJF and pcalJF regions of the Acinetobacter calcoaceticus chromosome appears to contribute to frequent repair of mutations, including removal of a Tn5 insertion from pcaJ. Repaired nt sequences are the products of nonreciprocal genetic exchange. The length of donor catIJF nt tracts recovered in repaired pcaIJF DNA ranged from less than 315 nt to more than 881 nt. This evidence does not distinguish gene conversion from natural transformation as a cause of repair, but natural transformation does not appear to contribute significantly, because it, unlike the repair process, is inactive in the presence of DNase. High-frequency recombination between catIJF and pcaIJF raises the question of why DNA between these chromosomal regions is stable. It is possible that some of the recombinational processes associated with gene conversion are unlike those underlying natural transformation.

Acinetobacter calcoaceticus↗
PubMed1994

Acquisition of apparent DNA slippage structures during extensive evolutionary divergence of pcaD and catD genes encoding identical catalytic activities in Acinetobacter calcoaceticus.

The pca operon from the Gram- bacterium Acinetobacter calcoaceticus encodes all of the enzymes required for catabolism of protocatechuate to common intermediary metabolites. This report presents the 2754-nucleotide (nt) sequence of a HindIII restriction fragment containing pcaD, the 801-bp gene encoding beta-ketoadipate enol-lactone hydrolase I. The deduced primary structure of A. calcoaceticus PcaD shares 44% amino acid (aa) sequence identity with the aligned primary structure of CatD (beta-ketoadipate enol-lactone hydrolase II) from the same organism, and the overall nt sequence identity of the two genes is 51.8%. In the 56% of the genes where selection for identical aa residues was not imposed, pcaD and catD have diverged so extensively that nt sequence identity of the aligned segments is only 28.2%; the G+C contents of these segments from the respective genes differ by 8%. Conserved within the aligned PcaD and CatD aa sequences is a Ser residue corresponding to the nucleophile within the alpha/beta-fold of many hydrolytic enzymes. In this region of primary structure, PcaD and CatD appear to have maintained some different aa sequences derived from a common ancestor. Conservation of the different aa sequences during extreme evolutionary divergence suggests that separate segments of primary structure, conserved within either PcaD or CatD, may be functionally incompatible within recombinant enzymes. Consequently, selection for avoidance of genetic exchange between pcaD and catD could account for the thorough nt substitution in regions where identical aa were not selected. Sequence repetitions within pcaD suggest that the multiple mutations required for its extensive divergence from catD were achieved in part by acquisition of a complex DNA slippage structure.

Acinetobacter calcoaceticus↗
PubMed1994

Unusual G + C content and codon usage in catIJF, a segment of the ben-cat supra-operonic cluster in the Acinetobacter calcoaceticus chromosome.

The nucleotide (nt) sequence of a 5.3-kb DNA segment containing the Gram- Acinetobacter calcoaceticus catBCIJFD operon is reported. This information completes determination of a 16-kb nt sequence containing the twelve ben and cat structural genes encoding enzymes required for catabolism of benzoate via the beta-ketoadipate pathway. Many of these genes can be traced to a common ancestry with genes from other organisms containing DNA with widely divergent G + C content. The A. calcoaceticus ben and cat genes are arranged in a supra-operonic cluster containing one known regulatory gene and three additional open reading frames (ORFs) that may have regulatory functions. Thirteen of the ben and cat genes, including the three ORFs with unknown function, are typical for A. calcoaceticus in that they possess a G + C content of 44.9 +/- 2.5%. Three exceptional A. calcoaceticus genes (catI, catJ and catF) possess G + C contents of 56.5 +/- 1.3%. These differences in G + C content are reflected in the distinctive patterns of codon usage shared by catI, catJ and catF. Thus, the catIJF region, known to exchange genetic information with the pcaIJF region in the same chromosome directing isofunctional proteins associated with the beta-ketoadipate pathway, has avoided the evolutionary forces that conferred characteristics G + C content upon the other ben and cat genes in A. calcoaceticus.

Acinetobacter calcoaceticus↗
PubMed1994

Contrasting patterns of evolutionary divergence within the Acinetobacter calcoaceticus pca operon.

The six enzymes required for catabolism of protocatechuate to succinate and acetylCoA are encoded by the pca genes in the Gram-bacterium, Acinetobacter calcoaceticus. The clustered A. calcoaceticus cat genes encode an analogous set of enzymes associated with the metabolic dissimilation of catechol. The nucleotide (nt) sequences of pcaIJFB and pcaK, reported here, complete evidence showing that all of the pca structural genes are tightly grouped in the order pcaIJFBDKCHG within a single operon. The pcaIJF region is nearly identical in nt sequence to the A. calcoaceticus catIDJF region which exhibits a G+C content and a codon usage pattern exceptional for A. calcoaceticus. In contrast, pcaD, pcaC, pcaH and pcaG have diverged substantially from their evolutionary counterparts in the cat region; all of these divergent genes exhibit G+C contents and codon usage patterns that are typical for A. calcoaceticus. The pcaIJF and catIJF regions are known to exchange DNA sequence information, and this property may have contributed to their nt sequence conservation. The pcaK gene has no counterpart among known cat genes. The deduced amino-acid sequence of PcaK indicates that it may be a transmembrane protein associated with transport.

Acetyl Coenzyme A↗
PubMed1988

Synergistic interactions of ciprofloxacin and extended spectrum beta-lactams or aminoglycosides against Acinetobacter calcoaceticus ss. anitratus.

The susceptibility of 54 clinical isolates of Acinetobacter calcoaceticus ss. anitratus to 16 antimicrobial agents was determined in vitro with inoculum of 10(4) and 10(6) cfu by a standard agar dilution method. The most active agents were imipenem, SCH 34343, ciprofloxacin, difloxacin (A-56619), and A-56620. Only imipenem and Abbott quinolones (A-56619 and A-56620) remained active when tested with the heavier inoculum. Except for ticarcillin and ceftazidime, which showed only moderate activity, the extended-spectrum penicillins and cephalosporins, as well as aztreonam and aminoglycosides, were inactive against these highly resistant strains. Nine isolates were selected for combination studies of ciprofloxacin with seven beta-lactams and three aminoglycosides using a checkerboard agar dilution technique. Synergistic or additive interactions at clinically achievable concentrations were more common with amikacin (eight isolates), tobramycin (seven), ceftazidime (six), cefoperazone (six), and aztreonam (six), than with other agents, including mezlocillin (four), piperacillin (three), gentamicin (two), and cefsulodin (two). Antagonism was rare, only occurring with mezlocillin in a single strain. These data suggest that combinations of ciprofloxacin with these agents may be useful for some nosocomial multidrug resistant A. calcoaceticus ss. anitratus infections.

Acinetobacter↗
PubMed1996

Antimicrobial susceptibility of clinical isolates of Acinetobacter baumannii.

The in-vitro activity of 18 antimicrobial agents alone or in combination against 248 clinical isolates of Acinetobacter baumannii from Taiwan were tested by agar dilution. The MIC90S of ampicillin, amoxicillin, piperacillin, cefuroxime, cefotaxime, ceftriaxone, gentamicin, and amikacin were at least 128 mu g/ml. Ceftazidime, cefepime, sulbactam, clavulanic acid, and tazobactam presented moderate activity with MIC90S of 32, 16, 16, 32, and 32 mu g/ml, respectively. The increased activity of ampicillin/sulbactam, amoxicillin/clavulanic acid, and piperacillin/tazobactam was due to the intrinsic effect of sulbactam, clavulanic acid, and tazobactam, respectively. Imipenem, meropenem, and ciprofloxacin were the most active antimicrobial agents with MIC90S of 1, 1, and 0.5 mu g/ml, respectively. Nineteen isolates (7.7%) were resistant to all aminoglycosides and beta-lactam antibiotics, except carbapenems and ciprofloxacin. We are concerned about the multidrug resistance of A. baumannii in this study.

Acinetobacter↗
PubMed1990

Cell surface hydrophobicity of 88 clinical strains of Acinetobacter baumannii.

We studied the surface hydrophobicity of 88 Acinetobacter baumannii strains of clinical origin, using both salt aggregation and adherence to paraxylene tests. Strains were divided into 2 groups: the first included 65 strains isolated from various clinical samples (infected catheters, tracheal and bladder devices); the second included 23 strains isolated from skin obtained from healthy controls. High surface hydrophobicity was observed in 92% of the first group of strains and in only 5% of the second.

Acinetobacter↗
PubMed1994

Biotyping, ribotyping and esterase electrophoresis as epidemiological tools for Acinetobacter baumannii.

An epidemiological survey was carried out over a one-week period to assess the spread of Acinetobacter baumannii in a medical intensive care unit. Fifty strains were isolated from patients colonized or infected by the organism and from a hospital environment. These strains belonged to biotypes 9 or 18. The rRNA gene restriction patterns (using EcoRI and PvuII as restriction endonucleases) and the esterase electrophoretic profiles were determined on 31 strains, using as comparison strain isolates from another intensive care unit of our hospital and from two other French hospitals. Four EcoRI ribotypes, four PvuII ribotypes and six esterase profiles were identified. All biotype 9 strains isolated in our hospital presented the same ribotype after EcoRI digestion, the same ribotype after PvuII digestion and the same zymotype. The same observation was made on most of the biotype 18 strains. Biotyping is an appropriate method for screening of strains, and ribotyping and esterase electrophoresis could be used as additional methods to delineate outbreaks of nosocomial infections caused by A. baumannii.

Acinetobacter↗
PubMed2004

Structural roles of the active site iron(III) ions in catechol 1,2-dioxygenases and differential secondary structure changes in isoenzymes A and B from Acinetobacter radioresistens S13.

The reversible active site metal ion removal process for two catechol 1,2-dioxygenase isoenzymes (IsoA and IsoB) isolated from Acinetobacter radioresistens S13 has been monitored using circular dichroism and fluorescence spectroscopic techniques. IsoA and IsoB are homodimers, containing one iron(III) ion per subunit. Their amino acid sequence identity is 48.4%. Previous experiments suggested that structural diversities could be responsible for the differential thermal and pH stabilities of the two isoenzymes and of their distinct demetallation kinetics. The far-UV CD spectra of IsoA and IsoB catechol 1,2-dioxygenases from A. radioresistens S13 provide information on their secondary structures. IsoB appears to have a content of alpha-helices higher than IsoA. Upon metal ion removal, both proteins reversibly lose part of their secondary structure following distinct pathways. CD spectra simulations allowed us to estimate the content of alpha-helices, beta-sheets, and turns for each isoenzyme and to monitor the secondary structure rearrangements. The metal ion withdrawal has large influence on the secondary structure: in particular a significant reduction of alpha-helices content is observed for both isoenzymes. Intrinsic fluorescence emission spectra clearly support such results, adding information on the local environment changes of the tryptophan residues. The positioning of Trp250 in IsoB has been shown to be of particular interest for monitoring the local structure changes occurring upon metal ion removal. For the first time these studies allow to underline the role of active site iron ions on dioxygenases folding and stability, further evidencing the differences in structural assembling between the two isoenzymes from A. radioresistens S13.

Acinetobacter↗
PubMed2026

Air contamination and cross-room transmission of carbapenem resistant Acinetobacter baumannii in ICU.

Air contamination of carbapenem-resistant Acinetobacter baumannii (CRAB) was investigated in an ICU with genome sequencing. CRAB was recovered from air samples (n=13) and patients (n=9) and belonged to ST2 (n=16) or ST164 (n=6). Four of the 9 ST2 clones were associated with transmission through the air within rooms or cross-room. All ST164 isolates belonged to a common clone and were found in two rooms. CRAB air dispersal may cause cross-room transmission at a long distance.

Acinetobacter baumannii↗
PubMed2004

Cloning and expression of p-hydroxyphenylacetate 3-hydroxylase from Acinetobacter baumannii: evidence of the divergence of enzymes in the class of two-protein component aromatic hydroxylases.

The genes encoding for the reductase and oxygenase components of p-hydroxyphenylacetate 3-hydroxylase from Acinetobacter baumannii were cloned and expressed in an E. coli system. The recombinant enzymes were purified and shown to have the same catalytic properties as the native enzyme. Sequence analysis and biochemical studies indicate that the enzyme represents a novel prototype of enzyme in the two-protein component class of aromatic hydroxylases. The C2 component shows little similarity to other oxygenases in the same class, correlating with its uniquely broad flavin specificity. Analysis of the C1 reductase sequence indicates that the binding sites of flavin and NADH mainly reside in the N-terminal half while the C-terminal half may be responsible for HPA-stimulation of NADH oxidation.

Acinetobacter baumannii↗
PubMed2003

Structural and serological characterisation of the O-antigenic polysaccharide of the lipopolysaccharide from Acinetobacter baumannii strain 24.

Extraction of dry bacteria of Acinetobacter baumannii strain 24 by phenol-water yielded a lipopolysaccharide (LPS) that was studied by serological methods and fatty acid analysis. After immunisation of BALB/c mice with this strain, monoclonal antibody S48-3-13 (IgG(3) isotype) was obtained, which reacted with the LPS in western blot and characterized it as S-form LPS. Degradation of the LPS in aqueous 1% acetic acid followed by GPC gave the O-antigenic polysaccharide, whose structure was determined by compositional analyses and NMR spectroscopy of the polysaccharide and O-deacylated polysaccharide as [carbohydrate structure: see text] where QuiN4N is 2,4-diamino-2,4,6-trideoxyglucose and GalNAcA 2-acetamido-2-deoxygalacturonic acid. The amino group at C-4 of the QuipN4N residues is acetylated in about 2/3 of LPS molecules and (S)-3-hydroxybutyrylated in the rest.

Acinetobacter baumannii↗
PubMed2006

Structural elucidation of the core-lipid A backbone from the lipopolysaccharide of Acinetobacter radioresistens S13, an organic solvent tolerant Gram-negative bacterium.

The structure of the core oligosaccharide of the lipopolysaccharide from an organic solvent tolerant Gram-negative bacterium, Acinetobacter radioresistens S13, was investigated by chemical analysis, NMR spectroscopy and MALDI-TOF mass spectrometry. All the experiments were performed on the oligosaccharides obtained either by alkaline degradation or mild acid hydrolysis. The data showed the presence of two novel oligosaccharide molecules containing a trisaccharide of 3-deoxy-D-manno-octulopyranosonic acid in the inner core region and a glucose rich outer core whose structure is the following: [structure: see text] R=H in the main oligosaccharide and beta-Glc in the minor product. The bacterium was grown on aromatic (phenol and benzoic acid) and nonaromatic carbon sources and the core oligosaccharide resulted to occur always with this novel structure.

Acinetobacter↗