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At least 1,405 records · Page 78Linked to original sources
PubMed1989

Novel carbenicillin-hydrolyzing beta-lactamase (CARB-5) from Acinetobacter calcoaceticus var. anitratus.

A strain of Acinetobacter calcoaceticus var. anitratus highly resistant to ticarcillin but susceptible to ticarcillin in combination with clavulanic acid (2 mg/l) was found to produce a constitutive beta-lactamase. This enzyme was periplasmic with a characteristic substrate profile of a carbenicillin-hydrolyzing enzyme. Enzyme inhibition was detected with antiserum (anti-CARB-3), pCMB, cloxacillin, clavulanic acid and sulbactam. This novel enzyme with a molecular mass of 28,000 resembles other plasmid-mediated carbenicillinases (CARB) but differs in its apparent isoelectric point estimated as 6.3 and has been designated CARB-5 on this basis.

Acinetobacter↗
PubMed1993

Esterase from the oil-degrading Acinetobacter lwoffii RAG-1: sequence analysis and over-expression in Escherichia coli.

The est gene encoding an esterase from Acinetobacter lwoffii RAG-1 was cloned into E. coli under the control of the PL promoter of the phage lambda. The N-terminal sequence of the first 20 amino acids of the heterologous expressed esterase corresponded to that obtained from the nucleotide sequence. Antibodies prepared against the over-expressed recombinant esterase in E. coli were used to locate the enzyme primarily in the membrane fractions of A. lwoffii RAG-1. Comparison with homologous proteins from both eukaryotic and prokaryotic organisms suggest that the RAG-1 esterase exhibits sequence motifs characteristic of both serine proteases and of lipases.

Acinetobacter↗
PubMed1994

Azide-resistant mutants in Acinetobacter calcoaceticus A2 are defective in protein secretion.

Azide, an inhibitor of ATPase, and a specific inhibitor of protein export was used in order to select for protein secretion mutants in Acinetobacter calcoaceticus A2. Two such mutants were isolated that were azide-resistant and defective in the general protein transport system. The mutation also conferred additional phenotypic changes, including an inability to grow on minimal media or at 40 degrees C. The existence of protein secretion mutants with a selectable phenotype may be useful for the genetic study of protein export.

Acinetobacter calcoaceticus↗
PubMed1994

UDP-N-acetylglucosamine 1-carboxyvinyl-transferase from Acinetobacter calcoaceticus.

We have analyzed the sequence downstream of rpoN from Acinetobacter calcoaceticus and identified an open reading frame encoding a protein with high similarity to UDP-N-acetylglucosamine 1-carboxyvinyl-transferase (MurZ). Multicopy plasmids encoding this enzyme conferred phosphomycin resistance to A. calcoaceticus. The polar effect of a rpoN mutation on the phosphomycin resistance level suggests that murZ is, in part, cotranscribed with rpoN. These observations confirm that A. calcoaceticus represents the first exception from a conserved genetic context of rpoN observed in several other Gram-negative bacteria.

Acinetobacter calcoaceticus↗
PubMed1997

Identification and characterization of an aadB gene cassette at a secondary site in a plasmid from Acinetobacter.

Transformation studies showed that an aminoglycoside resistance gene, aadB, is carried on a 6.0-kb plasmid (pRAY) in a clinical isolate of Acinetobacter (strain SUN). The gene was cloned and sequenced. An analysis of the DNA sequencing data showed that although the aadB gene is part of cassette, it is not associated with an integron. Rather, the aadB cassette has recombined at a secondary site downstream of putative promoters on pRAY.

Acinetobacter↗
PubMed1997

Oxacillin-hydrolyzing beta-lactamase involved in resistance to imipenem in Acinetobacter baumannii.

Acinetobacter baumannii strain A148, a clinical isolate resistant to imipenem (MIC = 32 mg l-1), synthesized two beta-lactamases with pIs 6.3 and > 9.2. The pI 6.3 enzyme hydrolyzed the penicillins, including isoxazoylpenicillins, first-, second- and, to a lesser extent, third-generation cephalosporins. It was inhibited by chloride ions and by the penem beta-lactamase inhibitor BRL 42715. Clavulanate was a weak inhibitor and EDTA did not affect the beta-lactamase activity. This enzyme also hydrolyzed imipenem with a catalytic efficiency (Kcat/Km) of 1500 mM-1 s-1. Moreover, this purified beta-lactamase produced a positive microbiological clover-leaf test with imipenem. Therefore, the pI 6.3 beta-lactamase was considered to be involved in the imipenem resistance of A. baumannii strain A148.

Acinetobacter↗
PubMed1998

Presence of integrons in isolates of different biotypes of Acinetobacter baumannii from Chilean hospitals.

Class 1 and class 2 integrons were investigated by hybridisation in 100 isolates of multiresistant biotypes of Acinetobacter baumannii from Chilean hospitals. Most isolates of A. baumannii biotype 9, the prevalent biotype, harboured integrons of class 2 (Tn7-like) whereas no integrons were detected in infrequent biotypes. Integron-carrying isolates exhibited broader antibiotic resistance patterns as well as higher resistance levels to various antimicrobials.

Acinetobacter↗
PubMed1998

In vitro interaction of the IHF-like proteins Acinetobacter junii and Proteus vulgaris with ihf sites.

The ability of the IHF-like proteins of Acinetobacter junii and Proteus vulgaris to interact with the H' attP and pR' ihf sites of lambda DNA was investigated. IHF from A. junii and P. vulgaris was found to bind the examined ihf sites in a way similar to IHF from Escherichia coli as shown by gel mobility shift DNA binding assays and footprinting analysis. The three IHF proteins bound to the pR' ihf site that overlaps the-35 region of that promoter and in vitro repression of transcription by each IHF was observed. These results confirm that IHF-like proteins from Gram-negative bacteria can recognize the same specific DNA sequences and appear to be important in regulation of transcription.

Acinetobacter↗
PubMed1999

Characterization of the Acinetobacter baumannii Fur regulator: cloning and sequencing of the fur homolog gene.

Growth kinetics, siderophore activity and iron-regulated bacterial proteins of Acinetobacter baumannii BM2580 were studied in iron-restricted and iron-supplemented chemically defined media. Iron-regulated outer membrane proteins of 75 kDa and 80 kDa were expressed under iron-restricted conditions. Cloning and sequencing of the complete iron-uptake regulatory (fur) gene from A. baumannii BM2580 is reported for the first time. This gene is preceded by a single autoregulated promoter whose -10 region overlaps the Fur binding site. The open reading frame identified encodes a polypeptide consisting of 145 amino acids. The fur gene is followed by a divergent open reading frame coding for the C-terminus of a putative PilU protein. Sequence analysis indicates that the Fur protein of A. baumannii was 63% identical to the Escherichia coli Fur protein.

Acinetobacter↗
PubMed1999

Cloning and complete nucleotide sequence of Acinetobacter radioresistens CMC-1 AglyA gene encoding serine hydroxymethyltransferase.

A gene (AglyA) encoding serine hydroxymethyltransferase of Acinetobacter radioresistens CMC-1 was cloned and sequenced. Nucleotide sequence analysis of AglyA predicted a single open reading frame (ORF) of 1251 bp encoding a 417-amino acid polypeptide. Two putative MetR-like binding sites (5'-TGAAACATGAGCT) and (5'-TGAGCAAAGTTCA), centered at bp -123 and -95 relative to the +1 translation start site were found, which have six out of nine and eight out of nine nucleotides that match to the consensus sequence of Escherichia coli (5'-TGAANNT/ANNTTCA), respectively. The enzyme also showed a high level of homology to other sources of serine hydroxymethyltransferase proteins.

Acinetobacter↗
PubMed1999

Comparison of the electrooptical properties and specific respiratory activity of Acinetobacter calcoaceticum A-122.

The electrooptical (EO) properties of a cell suspension and the specific respiratory activity of cells towards p-nitrophenol (PNP) were compared during PNP metabolism in Acinetobacter calcoaceticum strain A-122. The frequency dependence of the suspension's turbidity changes due to cellular orientation (orientational spectra) at frequencies of an orienting electric field of 10-10,000 kHz was determined. Orientational spectral changes observed during PNP incubation of the cells were followed over the range of 10-502 kHz. There were linear relationships between the magnitude of the EO effect at a 502-kHz frequency and the concentration of PNP over the range of 0.1-0.8 mM, and between the specific respiratory activity of the cells and the concentration of PNP over the range of 0.1-1.0 mM. The knowledge gained from these studies suggests a direct relationship between alterations in the cellular EO properties and PNP metabolism.

Acinetobacter calcoaceticus↗
PubMed2000

Class I integrons containing a dhfrI trimethoprim resistance gene cassette in aquatic Acinetobacter spp.

The presence of antibiotic resistance gene cassettes in class I integrons was investigated in 24 sulfamethoxazole-resistant and -sensitive Acinetobacter isolates derived from two Danish freshwater trout farms. Integrons were detected in five isolates from one of the fish farms, and their inserts were characterised by DNA sequencing. Each isolate contained a dhfrI gene cassette encoding resistance to trimethoprim and an open reading frame orfC of unknown function identical to the content of an integron previously found in a clinical enterobacterial isolate. Among the five isolates, at least two different strains were differentiated based on phenotypic tests and randomly amplified polymorphic DNA analysis. To our knowledge, this is the first report and characterisation of an integron in environmental bacteria.

Acinetobacter↗
PubMed2001

Protein synthesis patterns in Acinetobacter calcoaceticus induced by phenol and catechol show specificities of responses to chemostress.

The proteins induced in Acinetobacter calcoaceticus by the potentially toxic growth substrates phenol and catechol were analyzed by 2D-electrophoresis of cell extracts and compared with those induced by heat shock and oxidative stress. Although both aromatic compounds are quite similar, the only difference being that catechol has an additional hydroxyl group, the responses obtained differed considerably. Phenol has greater lipophilicity and mainly induced heat shock proteins, whereas catechol, which causes the production of reactive oxygen species, predominantly induced oxidative stress proteins. Furthermore, some special proteins were induced by phenol or catechol, which might be useful as biomarkers for chemostress, and could be involved in the catalytic degradation of potentially toxic compounds.

Acinetobacter calcoaceticus↗
PubMed2001

Spontaneous mutations affecting transcriptional regulation by protocatechuate in Acinetobacter.

Positive selection yields Acinetobacter strains with a spontaneous mutation blocking catabolism of protocatechuate. For this study, the growth temperature during selection was lowered to 22 degrees C: growth at 37 degrees C was found to mask the role of the protocatechuate-responsive transcriptional regulator PcaU. The resulting mutants included those with amino acid substitutions useful for understanding PcaU structure and function, a 20-bp deletion whose repeated isolation suggested genetic instability of DNA in the putative PcaU operator, and a large deletion whose phenotype revealed that the supraoperonic cluster of genes for the protocatechuate branch of the beta-ketoadipate pathway extends to genes for the utilization of C(6)-C(10) straight-chain dicarboxylic acids including adipate.

Acinetobacter↗
PubMed2006

The role of ISAba1 in expression of OXA carbapenemase genes in Acinetobacter baumannii.

ISAba1 was found in all widespread clones of Acinetobacter baumannii in the United Kingdom. All isolates studied had a blaOXA-51-like carbapenemase gene; some also had blaOXA-23-like and/or blaOXA-58-like. Among isolates with blaOXA-51-like as sole carbapenemase gene, only those with ISAba1 adjacent to blaOXA-51-like were carbapenem resistant. Minor differences in blaOXA-51-like sequence were observed in resistant and susceptible isolates. Isolates with blaOXA-23-like in addition were consistently resistant to carbapenems; in all of these ISAba1 lay upstream of blaOXA-23-like, but was not associated with blaOXA-51-like. These results suggest that ISAba1 is providing the promoter for blaOXA-51-like and, probably, for blaOXA-23-like.

Acinetobacter baumannii↗
PubMed1975

Correlation between twitching motility and possession of polar fimbriae in Acinetobacter calcoaceticus.

Negatively stained preparations of 16 strains of Acinetobacter calcoaceticus were examined in the electron microscope. Five of the strains did and 11 of the strains did not exhibit twitching motility. Two of the non-twitching strains were substrains of twitching wild-type strains. All twitching strains were found to possess fimbriae with a diameter of approximately 50 A. These fimbriae were shown to be of polar origin except in one strain where, for technical reasons, the origin could not be determined with certainty. Polar fimbriae could not be demonstrated in any of the strains that did not exhibit twitching motility. The demonstration of polar fimbriae was only regularly possible during the exponential growth phase, presumably because the fimbriae are shed by the bacteria during later growth phases. During the study, methods were developed for securing exponentially growing bacteria in concentrations suited for the preparation of negatively stained cells for electron microscopy. Peritrichously arranged fimbriae with a diameter of approximately 30 A were demonstrated in nearly all strains studied, especially on cells in late growth phases. The occurrence of this kind of fimbriae was therefore not correlated with the occurrence of twitching motility.

Acinetobacter↗
PubMed2025

Identification of EppR, a Second Repressor of Error-Prone DNA Polymerase Genes in Acinetobacter baumannii.

Acinetobacter baumannii is an opportunistic pathogen causing several infections that are increasingly difficult to treat due to its ability to rapidly gain antibiotic resistances. These resistances can arise due to mutations through the activity of error-prone DNA polymerases, such as DNA polymerase V (DNA Pol V) in response to DNA damage. The regulation of the DNA damage response (DDR) in A. baumannii is not completely understood; the regulation of genes encoding multiple copies of DNA Pol V is not fully characterized. Through genome-wide mutagenesis, we have identified a novel TetR-like family regulator of the umuDC and umuC genes, which we have named Error-prone polymerase regulator (EppR). We have found that EppR represses the expression of the genes encoding DNA Pol V and itself through direct binding to an EppR motif in their promoters. Lastly, we show that EppR also regulates UmuDAb, previously identified as a regulator of genes encoding DNA Pol V. These two gene products are functionally required to ensure regulation of the expression of the two umuDC, the two umuC genes as well as the regulators umuDAb and eppR genes. With these results, we propose a model in which multiple transcription factors regulate the expression of all these genes.

Acinetobacter baumannii↗