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PubMed1985

Evolutionary implications of features of aromatic amino acid biosynthesis in the genus Acinetobacter.

Key enzymes of aromatic amino acid biosynthesis were examined in the genus Acinetobacter. Members of this genus belong to a suprafamilial assemblage of Gram-negative bacteria (denoted Superfamily B) for which a phylogenetic tree based upon oligonucleotide cataloging of 16S rRNA exists. Since the Acinetobacter lineage diverged at an early evolutionary time from other lineages within Superfamily B, an examination of aromatic biosynthesis in members of this genus has supplied important clues for the deduction of major evolutionary events leading to the contemporary aromatic pathways that now exist within Superfamily B. Together with Escherichia coli, Pseudomonas aeruginosa and Xanthomonas campestris, four well-spaced lineages have now been studied in comprehensive detail with respect to comparative enzymological features of aromatic amino acid biosynthesis. A. calcoaceticus and A. lwoffii both possess two chorismate mutase isozymes: one a monofunctional isozyme (chorismate mutase-F), and the other (chorismate mutase-P) a component of a bifunctional P-protein (chorismate mutase-prephenate dehydratase). While both P-protein activities were feedback inhibited by L-phenylalanine, the chorismate mutase-P activity was additionally inhibited by prephenate. Likewise, chorismate mutase-F was product inhibited by prephenate. Two isozymes of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase were detected. The major isozyme (greater than 95%) was sensitive to feedback inhibition by L-tyrosine, whereas the minor isozyme was apparently insensitive to allosteric control. Prephenate dehydrogenase and arogenate dehydrogenase activities were both detected, but could not be chromatographically resolved. Available evidence favors the existence of a single dehydrogenase enzyme, exhibiting substrate ambiguity for prephenate and L-arogenate.(ABSTRACT TRUNCATED AT 250 WORDS)

Acinetobacter↗
PubMed1975

Microbial assimilation of hydrocarbons. II. Intracytoplasmic membrane induction in Acinetobacter sp.

1. The induction of intracytoplasmic membranes was demonstrated to occur in Acinetobacter sp. when grown on hexadecane, heptadecane, and hexadec-1-ene. 2. Evidence for a physical relationship between the cytoplasmic hydrocarbon "pools" and the intracytoplasmic membranes is presented. 3. The specificity of cytoplasmic pooling of hydrocarbons and the induction of intracytoplasmic membranes was investigated in relationship to hydrocarbon oxidation. 4. These results suggests that both processes are required for the growth of Acinetobacter sp. on hydrocarbons.

Acinetobacter↗
PubMed1977

Assimilatory nitrate reductase from Acinetobacter calcoaceticus.

A soluble nitrate reductase from the bacterium Acinetobacter calcoaceticus grown on nitrate has been characterized. The reduction of nitrate to nitrite is mediated by an enzyme of 96000 molecular weight that can use as electron donors either viologen dyes chemically reduced with dithionite or enzymatically reduced with NAD(P)H, through specific diaphorases which utilize viologens as electron acceptors. Nitrate reductase activity is molybdenumdependent as shown by tungstate antagonistic experiments and is sensitive to--SH reagents and metal chelators such as KCN. The enzyme synthesis is repressed by ammonia. Moreover, nitrate reductase activity undergoes a quick inactivation either by dithionite and temperature or by dithionite in the presence of small amounts of nitrate. Cyanate prevents this inactivating process and can restore the activity once the inactivation had occurred, thus suggesting that an interconversion mechanism may participate in the regulation of Acinetobacter nitrate reductase.

Acinetobacter↗
PubMed1977

[Utilization of trimethylammonium-compounds by Acinetobacter calcoaceticus (author's transl)].

The utilization of carnitine and carnitine derivatives (O-acylcarnitines, carnitine carboxylderivatives) and structure-related trimethylammonium-compounds (betaines and nitrogen-bases) by Acinetobacter calcoaceticus was studied by means of the control of growth and the quantitative detection of metabolites. The strain grew only on L-carnitine, L-O-acylcarnitines, and gamma-butyrobetaine as the sole carbon sources. The utilization of these compounds and the growth correlated with the cleavage of the C-N bond and thereby with the formation of trimethylamin. D-Carnitine was metabolized, if an additional carbon source, like L-carnitine, was present in the incubation mixture, or if the bacteria were preincubated with L- or DL-carnitine, but no growth was observed on D-carnitine as the sole carbon source. The bacteria oxidized choline to glycinebetaine in the presence of additional carbon sources, glycinebetaine itself was not assimilated. With regard to the catabolism of quaternary nitrogen compounds Acinetobacter calcoaceticus shows a different pathway in comparison with other bacterial species metabolizing carnitine.

Acinetobacter↗
PubMed1989

Genes involved in the biosynthesis of PQQ from Acinetobacter calcoaceticus.

From a gene bank of the Acinetobacter calcoaceticus genome a plasmid was isolated that complements four different classes of PQQ- mutants. Subclones of this plasmid revealed that the four corresponding PQQ genes are located on a fragment of 5 kilobases. The nucleotide sequence of this 5 kb fragment was determined and by means of Tn5 insertion mutants the reading frames of the PQQ genes could be identified. Three of the PQQ genes code for proteins of Mr 29700 (gene I), Mr 10800 (gene II) and Mr 43600 (gene III) respectively. In the DNA region where gene IV was mapped however the largest possible reading frame encodes for a polypeptide of only 24 amino acids. A possible role for this small polypeptide will be discussed. Finally we show that expression of the four PQQ genes in Acinetobacter 1woffi and Escherichia coli lead to the synthesis of the coenzyme in these organisms.

Acinetobacter↗
PubMed1993

Properties of polyphosphatase of Acinetobacter johnsonii 210A.

Polyphosphatase, an enzyme which hydrolyses highly polymeric polyphosphates to Pi, was purified 77-fold from Acinetobacter johnsonii 210A by Q-Sepharose, hydroxylapatite and Mono-Q column chromatography. The native molecular mass estimated by gel filtration and native gel electrophoresis was 55 kDa. SDS-polyacrylamide gel electrophoresis indicated that polyphosphatase of Acinetobacter johnsonii 210A is a monomer. The enzyme was specific for highly polymeric polyphosphates and showed no activity towards pyrophosphate and organic phosphate esters. The enzyme was inhibited by iodoacetamide and in the presence of 10 mM Mg2+ by pyro- and triphosphate. The apparent Km-value for polyphosphate with an average chain length of 64 residues was 5.9 microM and for tetraphosphate 1.2 mM. Polyphosphate chains were degraded to short chain polymers by a processive mechanism. Polyphosphatase activity was maximal in the presence of Mg2+ and K+.

Acid Anhydride Hydrolases↗
PubMed1996

Biomass relationship to growth and phosphate uptake of Pseudomonas fluorescens, Escherichia coli and Acinetobacter radioresistens in mixed liquor medium.

The ability of Pseudomonas fluorescens, Escherichia coli and Acinetobacter radioresistens to remove phosphate during growth was related to the initial biomass as well as to growth stages and bacterial species. Phosphate was removed by these bacteria under favourable conditions as well as under unfavourable conditions of growth. Experiments showed a relationship between a high initial cell density and phosphate uptake. More phosphate was released than removed when low initial cell densities (10(2)-10(5) cells ml-1) were used. At a high initial biomass concentration (10(8) cells ml-1), phosphate was removed during the lag phase and during logarithmic growth by P. fluorescens. Escherichia coli, at high initial biomass concentrations (10(7) cells ml-1), accumulated most of the phosphate during the first hour of the lag phase and/or during logarithmic growth and in some cases removed a small quantity of phosphate during the stationary growth phase. Acinetobacter radioresistens, at high initial cell densities (10(6), 10(7) cells ml-1) removed most of phosphate during the first hour of the lag phase and some phosphate during the stationary growth phase. Pseudomonas fluorescens removed phosphate more than A. radioresistens and E. coli with specific average ranges from 3.00-28.50 mg L-1 compared to average ranges of 4.92-17.14 mg L-1 for A. radioresistens and to average ranges of 0.50-8.50 mg L-1 for E. coli.

Acinetobacter↗
PubMedDate not supplied

Ciprofloxacin in the treatment of nosocomial multiply resistant Acinetobacter calcoaceticus bacteremia.

Twelve cases of multiply resistant Acinetobacter calcoaceticus bacteremia occurred in three intensive care units in three different outbreaks. All patients were mechanically ventilated, on broad spectrum antibiotics and had central lines when bacteremia occurred. The sites of primary infection were: abdominal (n = 3); respiratory (n = 4); central lines (n = 4); CNS (n = 1). In eight cases the acinetobacter strains were susceptible to ciprofloxacin only. Four other strains were sensitive to amikacin as well. All 11 patients treated with ciprofloxacin alone (seven) or in combination with amikacin (four) fully recovered from the infection. The 12th patient died before antibiotic susceptibility was available. Ciprofloxacin seems to be an excellent therapeutic agent for A. calcoaceticus infections.

Acinetobacter Infections↗
PubMed1996

Emergence of resistant isolates of Acinetobacter calcoaceticus- A. baumannii complex in a Spanish hospital over a five-year period.

Acinetobacter calcoaceticus-A. baumannii complex species have emerged as a relevant cause of nosocomial infection and colonization over the past 20 years, mainly in intensive care units. The aim of this study was to investigate the in vitro activity of 14 antimicrobial agents against 177 clinical isolates from patients admitted to a Spanish teaching hospital over a five-year period. Susceptibility rates or 99%, 99%, and 74% were obtained for imipenem, meropenem, ampicillin plus sulbactam, and amikacin, respectively. Increases in resistance were detected mainly for ticarcillin, piperacillin plus tazobactam, ceftazidime, amikacin, and ofloxacin. These results indicate that treatment of nosocomial infections due to Acinetobacter calcoaceticus-A. baumannii complex strains may be difficult.

Acinetobacter calcoaceticus↗
PubMed1985

Enzymatic profile of clinical isolates of Acinetobacter calcoaceticus.

The enzymatic profiles of 109 clinical isolates of Acinetobacter calcoaceticus subsp. anitratus and lwoffi were determined with conventional plate tests and the rapid API ZYM system (Analytab Products, Plainview, N.Y.). The majority of strains tested lacked DNase, hemolysin, protease, elastase and gelatinase. Strong enzymatic activities of butyrate esterase (C4), caprylate esterase (C8) and leucine arylamidase were detected in all isolates. No trypsin, chymotrypsin, alkaline phosphatase or glucosidase activities were present. This profile was characteristic of all isolates examined by the API ZYM system and could serve as a useful diagnostic feature of Acinetobacter calcoaceticus subsp. anitratus and subsp. lwoffi.

Acinetobacter↗
PubMed2003

Genetic organization of genes encoding phenol hydroxylase, benzoate 1,2-dioxygenase alpha subunit and its regulatory proteins in Acinetobacter calcoaceticus PHEA-2.

Acinetobacter calcoaceticus PHEA-2 is a phenol-degrading bacterium isolated from the wastewater from an oil refinery. A 10-kb XhoI fragment consisting of nine complete Open Reading Frames (ORFs) and one partial ORF was screened from a lambda library of PHEA-2 by Southern hybridization. The sequence analyses revealed that ORF2-ORF7, designated mphKLMNOP, are homologous to dmpKLMNOP of Pseudomonas sp. CF600 and mopKLMNOP of Acinetobacter calcoaceticus NCIB8250, sharing 38%-72% and 58.5%-93.5% respectively. The products encoded by dmp and mop genes convert phenol to catechol. The mph-operon and downstream ORFs, ORF9 and ORF10, sharing high identities to benM and benA, which encode ben-operon regulatory protein and benzoate 1,2-dioxygenase alpha subunit respectively, are separated by ORF8, whose function is unknown. The organization of the mph and ben operons is different from that described previously.

Acinetobacter calcoaceticus↗
PubMed2003

Gene cloning, sequencing, and expression of an esterase from Acinetobacter lwoffii I6C-1.

The esterase-encoding gene, estA, was cloned from Acinetobacter lwoffii I6C-1 genomic DNA into Escherichia coli BL21(DE3) with plasmid vector pET-22b (pEM1). pEM1 has a 4.4-kb EcoRI insert that contained the complete estA gene. A 2.4-kb AvaI- SphI DNA fragment was subcloned (pEM3) and sequenced. estA gene encodes a protein of 366 amino acids (40,687 Da) with a pI of 9.17. The EstA signal peptide was 31 amino acids long, and the mature esterase sequence is 335 amino acids long (37.5 kDa). The conserved catalytic serine residue of EstA is in position 210. The EstA sequence was similar to that of the carboxylesterase from Acinetobacter calcoaceticus (75% identity, 85% similarity), Archaeoglobus fulgidus (37% identity, 59% similarity), and Mycobacterium tuberculosis (35% identity, 51% similarity). These enzymes contained the conserved motif G-X(1)-S-X(2)-G carrying the active-site serine of hydrolytic enzyme. The EstA activity in A. lwoffii I6C-1 remains constant throughout the stationary phase, and the activity in E. coil BL21 (DE3) with pEM1 was similar to A. lwoffii I6C-1.

Acinetobacter↗
PubMed2004

Acinetobacter lipases: molecular biology, biochemical properties and biotechnological potential.

Lipases (EC 3.1.1.3) have received increased attention recently, evidenced by the increasing amount of information about lipases in the current literature. The renewed interest in this enzyme class is due primarily to investigations of their role in pathogenesis and their increasing use in biotechnological applications. Also, many microbial lipases are available as commercial products, the majority of which are used in detergents, cosmetic production, food flavoring, and organic synthesis. Lipases are valued biocatalysts because they act under mild conditions, are highly stable in organic solvents, show broad substrate specificity, and usually show high regio- and/or stereo-selectivity in catalysis. A number of lipolytic strains of Acinetobacter have been isolated from a variety of sources and their lipases possess many biochemical properties similar to those that have been developed for biotechnological applications. This review discusses the biology of lipase expression in Acinetobacter, with emphasis on those aspects relevant to potential biotechnology applications.

Acinetobacter↗
PubMed1979

Community-acquired acinetobacter pneumonia.

Acinetobacter calcoaceticus var anitratus, a nonfermentative grampnegative bacillus, has been infrequently reported as a cause of community-acquired pneumonia. In this paper we describe the course of six recent patients with community-acquired, bacteremic pneumonia due to this organism and review the six previously reported cases. Our experience suggests this organism is a more common cause of community-acquired pneumonia than previously thought. Acinetobacter pneumonia occurs in older persons with chronic disease, especially alcoholism. It is a fulminant illness with respiratory distress, hypoxemia, leukopenia and shock. Chest roentgenograms reveal a lobar or bronchopneumonic infiltrate which often becomes bilateral within 24 hours of admission to the hospital. Pleural effusions are common. The mortality rate is 43 per cent. Factors that predict a fatal outcome are granulocytopenia, empyema and therapy with inappropriate antibiotics. Therapy with appropriate antibiotics, especially carbenicillin and an aminoglycoside, increases survival.

Acinetobacter Infections↗
PubMed1985

Interconvertible molecular-weight forms of the bifunctional chorismate mutase-prephenate dehydratase from Acinetobacter calcoaceticus.

Acinetobacter calcoaceticus belongs to a large phylogenetic cluster of gram-negative procaryotes that all utilize a bifunctional P-protein (chorismate mutase-prephenate dehydratase) [EC 5.4.99.5-4.2.1.51] for phenylalanine biosynthesis. These two enzyme activities from Ac. calcoaceticus were inseparable by gel-filtration or DEAE-cellulose chromatography. The molecular weight of the P-protein in the absence of effectors was 65,000. In the presence of L-tyrosine (dehydratase activator) or L-phenylalanine (inhibitor of both P-protein activities), the molecular weight increased to 122,000. Maximal activation (23-fold) of prephenate dehydratase was achieved at 0.85 mM L-tyrosine. Under these conditions, dehydratase activity exhibited a hysteretic response to increasing protein concentration. Substrate saturation curves for prephenate dehydratase were hyperbolic at L-tyrosine concentrations sufficient to give maximal activation (yielding a Km,app of 0.52 mM for prephenate), whereas at lower L-tyrosine concentrations the curves were sigmoidal. Dehydratase activity was inhibited by L-phenylalanine, and exhibited cooperative interactions for inhibitor binding. A Hill plot yielded an n' value of 3.1. Double-reciprocal plots of substrate saturation data obtained in the presence of L-phenylalanine indicated cooperative interactions for prephenate in the presence of inhibitor. The n values obtained were 1.4 and 3.0 in the absence or presence of 0.3 mM L-phenylalanine, respectively. The hysteretic response of chorismate mutase activity to increasing enzyme concentration was less dramatic than that of prephenate dehydratase. A Km,app for chorismate of 0.63 mM was obtained. L-Tyrosine did not affect chorismate mutase activity, but mutase activity was inhibited both by L-phenylalanine and by prephenate. Interpretations are given about the physiological significance of the overall pattern of allosteric control of the P-protein, and the relationship between this control and the effector-induced molecular-weight transitions. The properties of the P-protein in Acinetobacter are considered within the context of the ubiquity of the P-protein within the phylogenetic cluster to which this genus belongs.

Acinetobacter↗
PubMed1994

A gene of Acinetobacter calcoaceticus BD413 encodes a periplasmic peptidyl-prolyl cis-trans isomerase of the cyclophilin sub-class that is not essential for growth.

Downstream of the Acinetobacter calcoaceticus estA gene, encoding a cell-bound esterase, an open reading frame (orf) was identified, which may encode a protein with a mass of 20.4 kDa. This protein shows extensive similarity to both prokaryotic and eukaryotic peptidyl-prolyl cis-trans isomerases (PPIases) of the cyclophilin sub-class, especially to the periplasmic rotamase (RotA) of Escherichia coli. A putative signal sequence suggests that the product of the Acinetobacter gene, we termed rotA, is located outside the cytoplasm. Transcription of the gene is initiated from a promoter, just upstream of the rotA orf. The observation that two A. calcoaceticus rotA deletion mutants display no apparent mutant phenotype, suggests that this PPIase is not essential for growth of the organism. These mutants, to our knowledge, are the first prokaryotic PPIase mutants reported.

Acinetobacter calcoaceticus↗
PubMed1989

Factors influencing the detachment of a polymer-associated Acinetobacter sp. from stainless steel.

The role of an extracellular polymer secreted by an Acinetobacter sp. attached to stainless steel was investigated. Parameters expected to influence polymer conformation, viz. temperature, pH, ionic strength and the concentration of calcium and magnesium ions, were altered and the resulting detached bacteria enumerated. Increasing both the temperature and pH resulted in increased numbers of bacteria detached. The effects of increasing the concentration of sodium chloride up to 100 mM and magnesium or calcium chloride up to 30 mM were small and, although statistically significant, were considered unlikely to have had major influence on the association of the bacteria with the stainless steel surfaces. Treatments including ultraviolet irradiation of surface-associated bacteria always resulted in removal of greater numbers of bacteria when compared to treatments where irradiation was not employed. The results indicate that an adhesive extracellular acidic polysaccharide may mediate the attachment of the Acinetobacter sp. to stainless steel.

Acinetobacter↗