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PubMed1985

The degradation of 1-phenylalkanes by an oil-degrading strain of Acinetobacter lwoffi.

An oil-degrading bacterium identified as Acinetobacter lwoffi was isolated by elective culture on North Sea Forties crude oil from an activated sludge sample. It grew on a wide range of n-alkanes (C12-C28) and 1-phenylalkanes, including 1-phenyldodecane, 1-phenyltridecane and 1-phenyltetradecane. The organism degraded 1-phenyldodecane to phenylacetic acid which was further metabolized via homogentisic acid, whilst 1-phenyltridecane was transformed to trans-cinamic and 3-phenylpropionic acid which were not further metabolized. Evidence is presented for a relationship between aromatic amino acid catabolism and 1-phenyldodecane degradation in this organism.

Acinetobacter↗
PubMed1982

Different forms of quinoprotein aldose-(glucose-) dehydrogenase in Acinetobacter calcoaceticus.

The ratios of the oxidation rates of aldose sugars, determined in cell-free extracts of Acinetobacter calcoaceticus, vary with the strain and growth conditions used. Three distinct forms of glucose dehydrogenase with different substrate specificities, occurring in variable proportions in these extracts, are responsible for this effect. One form is the already known "soluble glucose dehydrogenase", the other two forms are complexes containing enzyme and components of the respiratory chain. The proportions in which the enzyme forms are found in the cell-free extract correlate with the oxidative behaviour of whole cells with respect to aldose sugars, It is concluded, therefore, that the enzyme forms are not an artefact of the isolation procedure but that they exist as such in vivo. Since the two complexes can be converted into the soluble enzyme form, aldose dehydrogenase can, probably, be integrated in three different ways into the respiratory chain. The presence of glucose during growth does not stimulate aldose dehydrogenase production. This is not surprising since the enzyme has no function is carbon metabolism, except perhaps in strains growing on pentoses at high pH. Therefore, the physiological role of quinoprotein aldose dehydrogenase in this organism may be primarily in energy generation.

Acinetobacter↗
PubMed1995

Effect of carbon:nitrogen ratio on kinetics of phenol biodegradation by Acinetobacter johnsonii in saturated sand.

In polluted soil or ground water, inorganic nutrients such as nitrogen may be limiting, so that Monod kinetics for carbon limitation may not describe microbial growth and contaminant biodegradation rates. To test this hypothesis we measured 14CO2 evolved by a pure culture of Acinetobacter johnsonii degrading 120 micrograms 14C-phenol per ml in saturated sand with molar carbon:nitrogen (CN) ratios ranging from 1.5 to 560. We fit kinetics models to the data using non-linear least squares regression. Phenol disappearance and population growth were also measured at CN1.5 and CN560. After a 5- to 10-hour lag period, most of the 14CO2 evolution curves at all CN ratios displayed a sigmoidal shape, suggesting that the microbial populations grew. As CN ratio increased, the initial rate of 14CO2 evolution decreased. Cell growth and phenol consumption occurred at both CN1.5 and CN560, and showed the same trends as the 14CO2 data. A kinetics model assuming population growth limited by a single substrate best fit the 14CO2 evolution data for CN1.5. At intermediate to high CN ratios, the data were best fit by a model originally formulated to describe no-growth metabolism of one substrate coupled with microbial growth on a second substrate. We suggest that this dual-substrate model describes linear growth on phenol while nitrogen is available and first-order metabolism of phenol without growth after nitrogen is depleted.

Acinetobacter↗
PubMed1989

Quinoprotein D-glucose dehydrogenases in Acinetobacter calcoaceticus LMD 79.41: purification and characterization of the membrane-bound enzyme distinct from the soluble enzyme.

Acinetobacter calcoaceticus is known to contain soluble and membrane-bound quinoprotein D-glucose dehydrogenases while other oxidative bacteria such as Pseudomonas or Gluconobacter contain only membrane-bound enzyme. The two different forms were believed to be the same enzyme or interconvertible. Present results show that the two different forms of glucose dehydrogenase are distinct from each other in their enzymatic and immunological properties as well as in their molecular size. The soluble and membrane-bound glucose dehydrogenases were separated after French press-disruption by repeated ultracentrifugation, and then purified to nearly homogeneous state. The soluble enzyme was a polypeptide of 55 Kdaltons, while the membrane-bound enzyme was a polypeptide of 83 Kdaltons which is mainly monomeric in detergent solution. Both enzymes showed different enzymatic properties including substrate specificity, optimum pH, kinetics for glucose, and reactivity for ubiquinone-homologues. Furthermore, the two enzymes could be distinguished immunochemically; the membrane-bound enzyme is cross-reactive with an antibody raised against membrane-bound enzyme purified from Pseudomonas but not with antibody elicited against the soluble enzyme, while the soluble enzyme is not cross-reactive with the antibody of membrane-bound enzyme. Data also suggest that the membrane-bound enzyme functions by linking to the respiratory chain via ubiquinone though the function of the soluble enzyme remains unclear.

Acinetobacter↗
PubMed1995

Phosphate uptake by immobilized Acinetobacter calcoaceticus cells in a full scale activated sludge plant.

An in situ study of the P-uptake ability of Acinetobacter calcoaceticus was carried out using the alginate immobilization technique. Immobilized A. calcoaceticus cells displayed a high P-uptake ability (> 97% P-accumulating cells) when immersed in the aerobic zone of an activated sludge system for 30-240 min. The overall P-accumulation pattern of the anaerobic zone depicted a typical P-release mechanism. However, limited P-accumulation was also observed at this stage. Growth and anaerobiosis were not prerequisites for P-uptake. The immobilized cell retention time in the anaerobic zone did not affect remarkably the inherent P-uptake ability of immobilized A. calcoaceticus when exposed to the aerobic stage. P-uptake and release were reversible and depended on the environmental conditions to which immobilized cells were exposed. Immobilization of A. calcoaceticus using alginate can be regarded as a reliable method of studying pure cultures in the activated sludge process.

Acinetobacter calcoaceticus↗
PubMedDate not supplied

An outbreak of Acinetobacter calcoaceticus infection in a neonatal care unit.

Between January and December 1988, 383 neonates were admitted to our neonatal intensive care unit. 1,991 swabs and blood cultures were tested bacteriologically. Among them 90 specimens obtained from 41 patients were positive for Acinetobacter calcoaceticus. During this period we discovered and treated three cases with A. calcoaceticus sepsis. Three additional cases had blood cultures positive for this bacterium without demonstrating any clinical signs of infection. There is good evidence that contaminated warm air humidifiers were the source of infection. A review of microbiological data for several months preceding the outbreak showed a definite increase in the presence of A. calcoaceticus. The affected neonates required specific antibiotic therapy and intensive care. All of them survived. Conditions favoring the spread of these generally non-pathogenic bacteria and modes of preventive measures are discussed. The necessity of continuous bacteriological surveillance and careful disinfection of intensive care equipment is emphasized.

Acinetobacter Infections↗
PubMed1983

Acinetobacter mediastinitis and pneumonia in a thorotrastoma patient. The oropharyngeal flora as source of infection.

A case of bilateral pneumonia, mediastinitis and septicaemia caused by Acinetobacter calcoaceticus and Candida albicans is described. The infections occurred after a palliative operation for an esophagotracheal fistula in a thorotrastoma patient. The oropharynx was colonized by the two microorganisms at admission and is presented as the source of these infections. Clinical management and antimicrobial policy, including oropharyngeal decontamination, leading to a good outcome are reported.

Acinetobacter Infections↗
PubMed1989

Selection of glucose-assimilating variants of Acinetobacter calcoaceticus LMD 79.41 in chemostat culture.

Glucose metabolism has been studied in two strains of Acinetobacter calcoaceticus. Strain LMD 82.3, was able to grow on glucose and possessed glucose dehydrogenase (EC 1.1.99.17). Glucose oxidation by whole cells was stimulated by PQQ, the prosthetic group of glucose dehydrogenase. PQQ not only increased the rate of glucose oxidation and gluconic acid production but also shortened the lag phase for growth on glucose. Strain LMD 79.41 also possessed glucose dehydrogenase but was unable to grow on glucose. Batch cultures and carbon-limited chemostat cultures growing on acetate in the presence of glucose oxidized the sugar to gluconic acid, which was not further metabolized. However, after prolonged cultivation on mixtures of acetate and glucose, carbon-limited chemostat cultures suddenly acquired the capacity to utilize gluconate. This phenomenon was accompanied by the appearance of gluconate kinase and a repression of isocitrate lyase synthesis. In contrast to the starter culture, cells from chemostats which had been fully adapted to gluconate utilization, were able to utilize glucose as a sole carbon and energy source in liquid and solid media.

Acetates↗
PubMed1989

Effects of growth rate and oxygen tension on glucose dehydrogenase activity in Acinetobacter calcoaceticus LMD 79.41.

The regulation of the synthesis of the quinoprotein glucose dehydrogenase (EC 1.1.99.17) has been studied in Acinetobacter calcoaceticus LMD 79.41, an organism able to oxidize glucose to gluconic acid, but unable to grow on both compounds. Glucose dehydrogenase was synthesized constitutively in both batch and carbon-limited chemostat cultures on a variety of substrates. In acetate-limited chemostat cultures glucose dehydrogenase levels and the glucose-oxidizing capacity of whole cells were dependent on the growth rate. They strongly increased at low growth rates at which the maintenance requirement of the cells had a pronounced effect on biomass yield. Cultures grown on a mixture of acetate and glucose in carbon and energy-limited chemostat cultures oxidized glucose quantitatively to gluconic acid. However, during oxygen-limited growth on this mixture glucose was not oxidized and only very low levels of glucose dehydrogenase were detected in cell-free extracts. After introduction of excess oxygen, however, cultures or washed cell suspensions almost instantaneously gained the capacity to oxidize glucose at a high rate, by an as yet unknown mechanism.

Acinetobacter↗
PubMed1989

Cloning, characterization and DNA sequencing of the gene encoding the Mr 50,000 quinoprotein glucose dehydrogenase from Acinetobacter calcoaceticus.

Recently we described the cloning of the gene coding for a Mr 87,000 glucose dehydrogenase (GDH-A) from Acinetobacter calcoaceticus. In this report we describe the cloning of a gene coding for a second GDH (GDH-B) with a Mr of 50,000 from the same organism. This gene was isolated using a 20-mer synthetic oligonucleotide, derived from the N-terminal amino acid sequence of purified GDH-B as a probe to screen a genomic bank. From the DNA sequence of the gdhB gene, a protein can be derived of Mr 52,772 with a 24 amino acid signal peptide which is removed, resulting in the mature protein with a Mr 50,231. In vitro transcription-translation of the gdhB clone shows the mature and the precursor protein. The derived amino acid sequence has no obvious homology with GDH-A of A. calcoaceticus. We show that disaccharides are specific GDH-B substrates and that 2-deoxyglucose is specific for GDH-A.

Acinetobacter↗
PubMed1998

Outbreak of nosocomial Acinetobacter baumannii bacteremia in a high risk ward.

Acinetobacter baumannii is emerging as a major cause of nosocomial infections particularly in high risk patients. Being resistant to adverse environmental conditions, it can stay for prolonged periods in the hospital environment. We report an outbreak in the medical oncology ward where nine patients suspected of bacteraemia were blood culture positive for A. baumannii from the two samples each, one collected through the i.v. cannula and another through the peripheral veneous puncture. The bacteria was also isolated from the environmental sources from the various samples collected. The biotype, antibiogram, cellular protein profiles on SDS-PAGE and the restriction enzyme analysis patterns of the patient isolates and the environmental isolates were similar. This points to the environment as a source of infection. With reinforcement of proper barrier nursing and use of disposable heparine ampoules it was possible to control the outbreak.

Acinetobacter Infections↗
PubMed1982

Sensitivity of cultured pancreatic carcinoma cells to Acinetobacter glutaminase-asparaginase.

Cultured human pancreatic carcinoma cells (MIA PaCa-2) have been shown previously to be very sensitive to E. coli L-asparaginase (EC II). The present studies have demonstrated that another enzyme, Acinetobacter glutaminase-asparaginase (AGA) is much more effective in inhibiting cell growth. At the concentration of 0.0025 U/ml of AGA activity the enzyme totally inhibited cell growth, whereas the EC II with the same concentration did not show any effect. The inhibition of cell growth correlated well with inhibition of protein and glycoprotein synthesis. The addition of L-glutamine at the concentration of 1 mM completely reversed the inhibition of protein synthesis. Similarly, the addition of L-glutamine at the concentration of 3 mM daily on 3 successive days after adding AGA resulted in significant reversal of growth inhibition. The results of this study indicate that the action of AGA on MIA PaCa-2 is, to a great extent, exerted through its L-glutaminase activity.

Acinetobacter↗
PubMed1999

Alterations in surface hydrophobicity of Acinetobacter baumannii induced by meropenem.

Six strains of Acinetobacter baumannii out of eleven strains tested revealed a strong hydrophobic character. This was demonstrated by adherence of bacteria to xylene in the range of 90-94%. Changes in surface hydrophobicity of these strains were studied after treatment with meropenem at subinhibitory concentrations (sub-MICs) (1/4, 1/8, 1/16 or 1/32 of the MICs). All strains showed a reduced adherence to xylene after the action of meropenem at 1/4 or 1/16 of the MICs. Hydrophobicity of the treated bacteria was decreased to 1.3-70% (1/16 of the MICs) or to 12-86% (1/4 of the MICs), depending on the strain. A decrease in surface hydrophobicity of three strains was also observed after their exposure to meropenem at 1/8 of the MICs (to 18-71% of the control values). Meropenem at 1/32 of the MICs practically did not affect bacterial hydrophobic properties, with the exception of one strain.

Acinetobacter↗
PubMed1975

The behaviour of NAD+ and NADH in Acinetobacter calcoaceticus during n-alkane assimilation.

The behaviour of the nicotinamide adenine dinucleotides NAD+ and NADH in Acinetobacter calcoaceticus during n-alkane assimilation was studied, acetate and succinate being used as reference carbon sources. The intracellular concentration of the two nucleotides was found to increase during the exponential growth phase, reaching its maximum in the phase of decreasing growth rates. In the exponential phase, the NAD+/NADH quotients were less than 1 and showed only unimportant variations. In the phase of decreasing growth rates, the concentration of NADH showed a distinct decrease, reaching its minimum in the stationary phase. Parallel to this, the concentration of NAD+ showed a continuous increase until the stationary phase was reached. This resulted in an increase, during the phase of decreasing growth rates, of the NAD+/NADH quotients to values greater than 1, similarly as recorded in the stationary phase. There were no fundamental differences in this behaviour between the individual carbon sources.

Acetates↗
PubMed1988

Elimination of mercury, cadmium and antibiotic resistance from Acinetobacter lwoffi and Micrococcus sp. at high temperature.

Resistance determinants for HgCl2 and CdCl2 were eliminated along with a number of antibiotic resistance factors from Acinetobacter lwoffi and Micrococcus sp. at 44 degrees C. These organisms were orginally resistant to HgCl2, merbromin, CdCl2, Pb(NO3)2, benzylpenicillin, erythromycin, carbenicillin, tetracycline and sulfadiazine. Four different types of mutants from A. lwoffi (type I to IV) and one type of mutant from Micrococcus sp. (type V) were obtained, depending on the loss of particular resistance factors for HgCl2, merbromin, CdCl2 and antibiotics. In general, frequency of elimination of all the missing markers was very low (in the range of 10(-3) per bacterium). However, the missing determinants did not revert spontaneously.

Acinetobacter↗
PubMed1998

The Acinetobacter calcoaceticus NCIB8250 mop operon mRNA is differentially degraded, resulting in a higher level of the 3' CatA-encoding segment than of the 5' phenolhydroxylase-encoding portion.

The 7.5-kb polycistronic mop mRNA is differentially degraded in Acinetobacter calcoaceticus. The 4.9-kb 5' portion of the transcript contains the genes mopKLMNOP, encoding the multi-component phenol hydroxylase, and its 5' end decays three times faster than the 2.3-kb 3' portion encoding catechol 1,2-dioxygenase (catA). Larger amounts of the catA mRNA than the mopKLMNOP mRNA are present in the cells as a result of this processing. The site for endonucleolytic cleavage is located in the intercistronic region between mopP and catA, and contains a potential stem-loop structure and a putative RNase E cleavage site. Decay of the mop mRNA in Escherichia coli depends on RNase E. Thus, we propose that an RNase E-like activity is also present in A. calcoaceticus. Expression of MopN, one polypeptide of the multi-component phenol hydroxylase, interferes with growth of A. calcoaceticus. Thus, harmful expression of MopN may be reduced by rapid decay of its mRNA, indicating that mRNA processing contributes to differential gene expression in the large mop operon of A. calcoaceticus NCIB8250.

Acinetobacter calcoaceticus↗
PubMed2006

Novel therapies of multidrug-resistant Pseudomonas aeruginosa and Acinetobacter spp. infections: the state of the art.

Gram-negative non-fermenting bacilli, particularly Pseudomonas aeruginosa and Acinetobacter spp., are important opportunistic pathogens in hosppitalized patients, contributing to their morbidity and mortality. Recently, a rapid increase in frequency of multidrug-resistant clinical strains is being recorded, making the available therapeutic options very limited. Apart from the development of novel classes of antimicrobials, there is renewed interest in the use of old agents or new combinations of available drugs. Numerous in vitro investigations have been reported on the efficacy of different antimicrobials; however, they should be evaluated in experimental infection models and clinical trials. Novel approaches are being investigated, such as inhibition of virulence factor expression by pathogens or inhibition of their metabolic pathways. The use of bacteriophages, particularly those genetically modified, remains an alternative option in the therapy of infections caused by multidrug-resistant strains. Several vaccines against P. aeruginosa are under development. Apart from therapy with antimicrobial agents, eradication of outbreaks comprises implementation of strict infection control measures and prudent use of antimicrobials.

Acinetobacter Infections↗
PubMed2001

Dependence of linkage of alleles on their physical distance in natural transformation of Acinetobacter sp. strain ADP1.

The interdependence of genetic linkage in transformation and physical distance was studied in the bacterium Acinetobacter sp. strain ADP1. Transformation experiments were performed using 17 strains containing different mutations within the 21-kb pca-qui-pob gene cluster as recipients for the DNA of one of two strains carrying a mutation causing a temperature-sensitive phenotype. The different phenotypes of the transformants (temperature-sensitive or wild-type-like) were used to evaluate linkage. Combination of the recipient and donor strains resulted in physical distances ranging from 2 bp to 10,533 bp. A logarithmic relationship of decreasing linkage and increasing distance was observed, thus leading to calibration of a system for analysis of physical distance derived from linkage data. Limitations of this application are described here: Certain mutations (3 out of 17 mutations used in this study) are an exception to the observed relationship and result in much lower linkage than expected. Observed DNA sequence repetitions leading to DNA rearrangements may be the cause of this anomaly.

Acinetobacter↗