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PubMed1995

Purification and characterization of Acinetobacter calcoaceticus 4-hydroxybenzoate 3-hydroxylase after its overexpression in Escherichia coli.

4-Hydroxybenzoate 3-hydroxylase [EC 1.14.13.2] from Acinetobacter calcoaceticus was purified to homogeneity following the 40-fold overexpression of this gene (pobA) in Escherichia coli. Overexpression was accomplished by placing the folA gene (encoding trimethoprim-resistant dihydrofolate reductase) directly downstream of the pobA gene, and demanding growth of recombinants on elevated concentration of trimethoprim. Presumably, the surviving variants have undergone a genetic alteration which allowed the overexpression of both folA and pobA. 4-Hydroxybenzoate 3-hydroxylase was purified in two chromatographic steps, characterized biochemically, and its properties were compared to those of its homolog from Pseudomonas fluorescens. The two enzymes differ in their response to Cl- ion inhibition. A single amino acid change in the putative NADPH-binding site is proposed to account for this difference. The inhibitory and catalytic properties of substrate analogs were also examined.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1995

Cloning and expression of dipeptidase from Acinetobacter calcoaceticus ATCC 23055.

The gene encoding dipeptidase was cloned from Acinetobacter calcoaceticus ATC 23055. Determination of the nucleotide sequence revealed that the gene had an open reading flame of 1,050 bp coding a protein of 350 amino acids. The deduced amino acid sequence showed 48.8% similarity to human renal dipeptidases and conserved two amino acid residues identified in human and pig renal dipeptidases as essential ones for the catalytic activity. Purified recombinant enzyme expressed in Escherichia coli did not hydrolyze the unsaturated dipeptide, glycyldehydrophenylalanine. On the other hand, it preferentially hydrolyzed dipeptides having a D-amino acid, when compared with those having an L-amino acid at the C-terminal. Furthermore, it could not hydrolyze tripeptides. These results indicate that the dipeptidase produced by A. calcoaceticus ATC 23055 has a unique substrate specificity and preferentially hydrolyzes dipeptides having a D-amino acid at the C-terminal.

Acinetobacter calcoaceticus↗
PubMed1984

Nucleotide sequence of the Acinetobacter calcoaceticus trpGDC gene cluster.

A plasmid library of Acinetobacter calcoaceticus HindIII fragments was constructed, and clones that complemented an Escherichia coli pabA mutant were selected. Plasmids containing a 3.9-kb fragment of A. calcoaceticus DNA that also complemented E. coli trpD and trpC-(trpF+) mutants were obtained. We infer that complementation of E. coli pabA mutants was the result of the expression of the amphibolic anthranilate-synthase/p-aminobenzoate-synthase glutamine-amidotransferase gene and that the plasmid insert carried the entire trpGDC gene cluster. In E. coli minicells, the plasmid insert directed the synthesis of polypeptides of 44,000, 33,000, and 20,000 daltons, molecular masses that are consistent with the reported molecular masses of phosphoribosylanthranilate transferase, indoleglycerol-phosphate synthase, and anthranilate-synthase component II, respectively. A 3,105-bp nucleotide sequence was determined. Comparison of the A. calcoaceticus trpGDC sequences with other known trp gene sequences has allowed insight into (1) the evolution of the amphibolic trpG gene, (2) varied strategies for coordinate expression of trp genes, and (3) mechanisms of gene fusions in the trp operon.

Acinetobacter↗
PubMed1990

An evolutionary comparison of Acinetobacter calcoaceticus trpF with trpF genes of several organisms.

The deduced amino acid sequence of Acinetobacter calcoaceticus N-(5'-phosphoribosyl) anthranilate isomerase (PRAI), which is coded by trpF, was compared with TrpF of Caulobacter crescentus, Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae, Neurospora crassa, and Aspergillus nidulans. Sixty percent of identical or similar amino acids were located in alpha/beta TIM (triose-phosphate isomerase) barrels and in residues important in substrate binding and catalysis. In addition, the analysis of trpF genes presented here supports a model by which fusion between separate trpC and trpF genes arose in some cases by in-frame deletions.

Acinetobacter↗
PubMedDate not supplied

Acinetobacter calcoaceticus variety anitratus: an increasing nosocomial problem.

Acinetobacter calcoaceticus var anitratus is an increasing nosocomial problem in some institutions. Duirng a recent 16-month period, we observed 15 patients with blood isolates of this organism. Thirteen of these patients acquired the organism from the hospital environment. Eleven of these represented real disease and concurrent growth of the organism from another site was predictive of infection (P less than 0.03). A review of laboratory records showed that there was a three-fold increase in nonblood isolates of this organism from hospitalized patients in 1975 and 1976, as compared to 1972 (P less than 0.0001), and a marked seasonal effect was noted, with increased isolations during the summer. Aminoglycoside resistance had increased considerably with 25% of nonblood isolates being resistant to gentamicin and 16% resistant to tobramycin despite its restriction; blood isolates were uniformly susceptible to gentamicin and tobramycin. Reporting of A anitratus as a nosocomial pathogen and serotyping of isolates may be useful to further define its role in nosocomial infections.

Acinetobacter Infections↗
PubMed1999

Mortality and the increase in length of stay attributable to the acquisition of Acinetobacter in critically ill patients.

OBJECTIVE: To determine the impact of Acinetobacter baumannii (AB) acquisition in intensive care unit (ICU) patients on mortality and length of stay (LOS). DESIGN: Pairwise matched 1:1 case-control study. SETTING: Medical-surgical ICU in a tertiary health care institution. PATIENTS: During 16 months, all patients admitted to the ICU were eligible. Case patients were defined as every patient with an AB isolation 48 hrs after ICU admission. Control patients were retrospectively selected from ICU patients without any AB isolation, according to seven matching variables. MEASUREMENTS AND MAIN RESULTS: Attributable mortality and excess LOS in the ICU were measured. Eighty-seven patients were included, with 75 pairs successfully matched. Infection was defined in 48 patients (23 respiratory). The attributable mortality rate for AB acquisition was 30% (49% vs.19%) (95% confidence interval [CI] = 23%, 37%): 43% (CI = 34%, 52%) in patients with infection (58% vs.15%) and 53% (CI = 41%, 65%) in patients with respiratory infections (70% vs.17%). The estimated risk rates for death were 2.6 (CI = 1.6, 4.5; p < .001), 4.0 (CI = 1.9, 8.3; p < .001), and 4.0 (CI = 1.6, 10.2; p < .01), respectively. The attributable excess LOS was 13 days for both AB acquisition and infection (23 vs. 10 days; p < .001) and respiratory infections (23 vs. 10 days; p < .01). In noninfected patients, no significant excess of mortality was found (33% vs. 26%), but LOS increased in 15 days. CONCLUSION: AB acquisition involved an excess LOS in ICU patients and increased risk of death, but the latter could be found only in patients with proven infection.

Acinetobacter Infections↗
PubMedDate not supplied

A novel antibacterial gene transfer treatment for multidrug-resistant Acinetobacter baumannii-induced burn sepsis.

Sepsis caused by multidrug-resistant bacterial infections in critically injured patients has become a major clinical problem. Recently, Acinetobacter baumannii (AB) wound infections, especially in our critically injured soldiers fighting in Iraq and Afghanistan, is posing a major clinical problem and an economic burden. ConjuGon, Inc., has developed a novel antibacterial therapeutic technology using bacterial conjugation. The donor cells are attenuated Escherichia coli carrying a conjugative plasmid. The expression of bactericidal genes cloned on the plasmid is tightly repressed in the donor cells but becomes de-repressed once mobilized into a pathogen and disrupts protein synthesis. Here, we tested the efficacy of this novel conjugation technology to control and eradicate a drug-resistant clinical isolate of AB wound infection both in vitro and in a murine burn sepsis model. C57Blk/6J mice were divided into burn (B) and burn sepsis (BS) groups. All animals received a 12% TBSA dorsal scald full-thickness burn. The BS group was inoculated with multidrug-resistant AB (1 x 10(5) colony-forming units [CFU]) at the burn wound site. BS animals were either untreated or treated with increasing concentrations (10(3) - 19(10) CFU) of attenuated donor E. coli encoding bactericidal proteins. The survival rate was monitored for 10 days. The ability of donor cells to significantly diminish AB levels in the burn wound 24 hours after injury was determined by quantitative cultures. Donor cells were highly effective in killing AB in vitro. In the burn sepsis model, 90% B group animals survived, and 40% to 50% BS animals survived with no treatment in 5 to 6 days. Treatment with donor cells at 10(10) to 10(6) provided significant survival advantage (P < .05). Quantitative cultures of burn wounds revealed that AB numbers increased from 3 x 10(4) CFU to 7.8 +/- 4.4 x 10(9) CFU in 24 hours in the untreated group. Single treatment with donor cells (10(10) CFU) significantly reduced AB in the burn wound to less than the levels seeded into the wound (1.23 +/- 0.5 x 10(4) CFU; P < .05). Taken together, these results indicate that this novel technology is an efficient method to control drug-resistant AB burn wound infections and prevent their systemic spread.

Acinetobacter baumannii↗
PubMed2000

Effect of EDTA on the resistance of clinical isolates of Acinetobacter baumannii to the bactericidal activity of normal human serum.

Acinetobacter baumannii is an opportunist nosocomial pathogen of world-wide importance and produces severe infections in immunocompromised patients. However, the virulence factors contributing to its pathogenic properties are not well known. The effect of normal human serum against 18 clinical isolates of the most prevalent biotypes of A. baumannii in Chile was investigated. The effect of pre-treatment of the cells with ethylene diamine tetraacetic acid (EDTA) or bismuth subsalicylate (BSS), compounds known to decrease the amount of lipopolysaccharide (LPS) and bacterial capsular polysaccharide (CPS), respectively, in other gram-negative bacteria, was evaluated. Most isolates (16 of 18) showed resistance to normal human serum. Prior treatment with EDTA rendered nine of these isolates susceptible to serum, while seven isolates maintained their resistance. Pre-treatment with BSS did not modify the serum-resistant behaviour of the isolates. The results suggest that LPS might be involved in the resistance of A. baumannii to human serum whereas CPS does not seem to contribute to this property.

Acinetobacter↗
PubMed2002

Nucleotide sequence of a ssRNA phage from Acinetobacter: kinship to coliphages.

The complete nucleotide sequence of ssRNA phage AP205 propagating in Acinetobacter species is reported. The RNA has three large ORFs, which code for the following homologues of the RNA coliphage proteins: the maturation, coat and replicase proteins. Their gene order is the same as that in coliphages. RNA coliphages or Leviviridae fall into two genera: the alloleviviruses, like Q(beta), which have a coat read-through protein, and the leviviruses, like MS2, which do not have this coat protein extension. AP205 has no read-through protein and may therefore be classified as a levivirus. A major digression from the known leviviruses is the apparent absence of a lysis gene in AP205 at the usual position, overlapping the coat and replicase proteins. Instead, two small ORFs are present at the 5' terminus, preceding the maturation gene. One of these might encode a lysis protein. The other is of unknown function. Other new features concern the 3'-terminal sequence. In all ssRNA coliphages, there are always three cytosine residues at the 3' end, but in AP205, there is only a single terminal cytosine. Distantly related viruses, like AP205 and the coliphages, do not have significant sequence identity; yet, important secondary structural features of the RNA are conserved. This is shown here for the 3' UTR and the replicase-operator hairpin. Interestingly, although AP205 has the genetic map of a levivirus, its 3' UTR has the length and RNA secondary structure of an allolevivirus. Sharing features with both MS2 and Q(beta) suggests that, in an evolutionary sense, AP205 should be placed between Q(beta) and MS2. A phylogenetic tree for the ssRNA phages is presented.

3' Untranslated Regions↗
PubMed1978

Chromosome mapping in Acinetobacter calcoaceticus.

RP4-mediated conjugation was used to map the loci of 23 different mutations on a circular linkage group in Acinetobacter calcoaceticus EBF65/65. The resulting genetic map indicated that the chromosomal organization of A. calcoaceticus differed from that of members of the enteric group of bacteria and was similar to Pseudomonas in showing an absence of clustering of functionally related genes.

Acinetobacter↗
PubMed1978

Mutants of Acinetobacter calcoaceticus NCIB 8250 constitutive for the mandelate enzymes.

Methods for isolating mutants of Acinetobacter calcoaceticus NCIB 8250 constitutive for the mandelate enzymes were compared. Non-inducing substrates were not available. Continuous culture gave no stable constitutive mutants. Alternate culture in inducing (L-mandelate) and non-inducing (L-glutamate) media led to the isolation of mutants mesoconstitutive for L-mandelate dehydrogenase and phenylgloxylate carboxy-lyase, and hyperinducible for benzaldehyde dehydrogenase I. Screening of possible anti-inducers showed that 2-phenyl-propionate was very effective; it was a competitive inhibitor of gratuitous induction by thiophenoxyacetate, and was used for the isolation of constitutive mutants. Some of the mutants were magnoconstitutive for L-mandelate dehydrogenase, phenylglyoxylate carboxylyase and benzaldehyde dehydrogenase I and could not be further induced; others had lower specific activities which could be increased by induction with phenylglyoxylate or thiophenoxyacetate. Similar constitutive mutants were derived from a mutant which lacked L-mandelate dehydrogenase.

Acinetobacter↗
PubMed1980

Naturally occurring plasmids in Acinetobacter calcoaceticus: a P class R factor of restricted host range.

A naturally occurring transmissible plasmid, designated pAV1, has been isolated in Acinetobacter calcoaceticus. It specifies resistance to sulphonamides and is capable of mobilizing two non-transmissible resistance determinants for tetracycline and neomycin, respectively, within strains of A. calcoaceticus. It is incompatible with the P class R factors RP4 and R751 in A. calcoaceticus. On this basis we conclude that pAV1 is a member of the P incompatibility group. However, unlike most other P group R factors, pAV1 is not transmissible to strains of Escherichia coli, Pseudomonas aeruginosa, Klebsiella or Proteus mirabilis.

Acinetobacter↗
PubMed1980

Gene transfer in Acinetobacter calcoaceticus: fertility variants of the sex factor pAV1.

The naturally occurring transmissible plasmid pAV1 mediates chromosome transfer and can exhibit two distinct levels of transmissibility in Acinetobacter calcoaceticus strain EBF65/65. The two states of pAV1 have been arbitrarily designated pAV1a (low frequency variant) and pAV1b (high frequency variant). Both variants have the same incompatibility and host range properties and each mobilizes two non-transmissible resistance determinants for tetracycline and neomycin. Sex factor activity has been shown to be stable: however, pAV1b fertility variants can be derived from pAV1a donors following conjugal transfer of pAV1 into new recipient strains of EBF65/65.

Acinetobacter↗
PubMed1980

Naturally occurring plasmids in Acinetobacter calcoaceticus: pAV2, a plasmid which influences the fertility of the sex factor pAV1.

Acinetobacter calcoaceticus strain EBF65/65 harbours a cryptic plasmid, pAV2, which has been shown by electrophoretic separation on agarose gels to have a molecular mass of approximately 13.5 megadaltons (Md). Transfer of the previously described sex factor pAV1 (Hinchliffe & Vivian, 1980 a,b) from the hospital strainJC17 into strains possessing pAV2 occurs only at a low frequency, whereas transfer to similar strains lacking pAV2 occurs at a much higher frequency. In EBF65/65, pAV1 may be present in strains possessing or lacking pAV2; pAV1 strains lacking pAV2 correspond to strains previously described as pAV1a (Hinchliffe & Vivian, 1980b) whereas pAV1 strains which also possess pAV2 correspond to pAB1b strains. The genetic evidence presented here is consistent with the hypothesis that pAV2 specifies a host restriction and modification system that is active against pAV1. Physical evidence from agarose gel electrophoresis indicates that pAV1 corresponds to a band of approximately 85 Md in strain JC17. The corresponding band in strains of EBF65/65 is difficult to distinguish because of the presence of a further cryptic plasmid band of approximately 88 Md, designated pAV3. A small cryptic plasmid of approximately 6 Md, designated pAV4, is reported for EBF65/65.

Acinetobacter↗
PubMed1980

Restriction mediated by pAV2 affects the transfer of plasmids in Acinetobacter calcoaceticus.

The naturally occurring plasmid pAV2 restricts the entry of the P class plasmid RP4 and the W class plasmids R388 and S-a into Acinetobacter calcoaceticus strain EBF65/65 from Escherichia coli. The W class plasmids only transfer from E. coli into pAV2-strains. Plasmid RP4 is modified in the presence of pAV2 such that it is no longer restricted on entry into pAV2 recipients of strain EBF65/65.

Acinetobacter↗
PubMed1980

Behaviour of bacteriophage Mu in Acinetobacter calcoaceticus EBF65/65.

Transfer of RP4::Mu plasmids from Escherichia coli K12 to Acinetobacter calcoaceticus EBF65/65 was very inefficient compared with RP4 and was only detectable to strains of EBF65/65 lacking pAV2, a cryptic plasmid thought to code for a restriction/modification system. RP4::Mu-derived plasmids transferred from pAV2-strains of EBF65/65 back to E. coli K12 were found to carry defective prophages which had lost the ability to produce detectable phage particles. Re-transfer of these defective plasmids from hsm kappa + and hsm kappa strains of E. coli K12 back to EBF65/65, when compared with the transfer of RP4, provided evidence for a second restriction/modification system in EBF65/65 which affected mainly Mu DNa. Using a mutant Mu prophage, Mu cts62 r23, it was possible to obtain RP4::Mu plasmids in EBF65/65 which were non-defective. These produced viable Mu particles when transferred back to E. coli K12 and could also be thermoinduced in EBF65/65; however, expression of Mu in EBF65/65 was very poor and plaques were only detected on a restrictionless strain of E. coli K12. 'Plasmid suicide by Mu' may enable the development of a method for directed chromosome mobilization in A. calcoaceticus.

Acinetobacter↗
PubMed1981

Quinoprotein alcohol dehydrogenase from a non-methylotroph, Acinetobacter calcoaceticus.

Acinetobacter calcoaceticus grown on ethanol contains an NAD(P)+-independent alcohol dehydrogenase which resembles methanol dehydrogenase from methylotrophic bacteria in many respects. Likewise, the prosthetic group of this enzyme appears to be identical to that of methanol dehydrogenase, namely, pyrrolo quinoline quinone. The organism is unable to grow on methanol, which means that quinoprotein alcohol dehydrogenases are not restricted to methylotrophs. Arguments are presented for the idea that quinoprotein alcohol dehydrogenases exist in other alkane- or alcohol-grown bacteria. Although the enzyme from A. calcoaceticus can be best compared with that from Rhodopseudomonas acidophila in that both have very low affinities for methanol and are activated by aliphatic amines, the two enzymes are immunologically and electrophoretically unrelated. Furthermore, the A. calcoaceticus enzyme shows the broadest substrate specificity hitherto known for this type of enzyme in that it also oxidizes higher aldehydes. The extent of hydration of aldehydes cannot account for the aldehyde substrate specificity of these enzymes but the concept of a dual substrate specificity for alcohols and aldehydes can explain this very well. The different properties of the two enzymes compared with those of methanol dehydrogenases cannot be ascribed to the presence of iron as both enzymes contained a negligible amount of this metal.

Acinetobacter↗
PubMed1981

The isolation of cell surface mutants of Acinetobacter calcoaceticus RAG-1.

The isolation of cell surface mutants of Acinetobacter calcoaceticus RAG-1 was demonstrated by a method based on the differential immunoprecipitating properties of wild-type cells and mutants. In the presence of antiserum, about 99% of wild-type cells in suspension sedimented following overnight agglutination. The kinetics of antiserum-induced agglutination was quantified by measuring the time-dependent decrease in turbidity. For mutant isolation, a sample of the cells remaining in the supernatant fluid served as inoculum for a fresh culture. This enrichment procedure of sequential growth and agglutination was repeated until the supernatant fluid following the overnight agglutination step remained turbid. Of the 40 colonies isolated in this manner, 34 exhibited altered agglutination properties. The agglutinability of wild-type cells varied with the phase of growth - cells harvested during the exponential phase were agglutinated better than those in stationary phase. In contrast, the antiserum-induced agglutination of most mutants was poor during the early phases of growth, but improved during late-stationary phase. One mutant failed to agglutinate in the presence of antiserum irrespective of the phase of growth.

Acinetobacter↗