Effects of surfactant mixtures, including Corexit 9527, on bacterial oxidation of acetate and alkanes in crude oil.
(1/123)
Mixtures of nonionic and anionic surfactants, including Corexit 9527, were tested to determine their effects on bacterial oxidation of acetate and alkanes in crude oil by cells pregrown on these substrates. Corexit 9527 inhibited oxidation of the alkanes in crude oil by Acinetobacter calcoaceticus ATCC 31012, while Span 80, a Corexit 9527 constituent, markedly increased the oil oxidation rate. Another Corexit 9527 constituent, the negatively charged dioctyl sulfosuccinate (AOT), strongly reduced the oxidation rate. The combination of Span 80 and AOT increased the rate, but not as much as Span 80 alone increased it, which tentatively explained the negative effect of Corexit 9527. The results of acetate uptake and oxidation experiments indicated that the nonionic surfactants interacted with the acetate uptake system while the anionic surfactant interacted with the oxidation system of the bacteria. The overall effect of Corexit 9527 on alkane oxidation by A. calcoaceticus ATCC 31012 thus seems to be the sum of the independent effects of the individual surfactants in the surfactant mixture. When Rhodococcus sp. strain 094 was used, the alkane oxidation rate decreased to almost zero in the presence of a mixture of Tergitol 15-S-7 and AOT even though the Tergitol 15-S-7 surfactant increased the alkane oxidation rate and AOT did not affect it. This indicated that there was synergism between the two surfactants rather than an additive effect like that observed for A. calcoaceticus ATCC 31012. (+info)
Genotypic and phenotypic similarity of multiresistant Acinetobacter baumannii isolates in the Czech Republic.
(2/123)
The diversity of 103 clinical isolates of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex obtained between 1991 and 1997 from 17 Czech hospitals was studied by ribotyping, biotyping, plasmid profiling and antibiotic susceptibility testing. According to the EcoRI ribotypes, all but one of these isolates were identified to the DNA group level: 77 isolates were allocated to DNA group 2 (A. baumannii), 14 to DNA group 3, 10 to DNA group 13 sensu Tjernberg and Ursing and one to DNA group 1 (A. calcoaceticus). In total, 50 different EcoRI ribotypes and 10 biotypes were observed. Plasmids were found in 92% of the isolates and a high variability in plasmid profiles was found in isolates of the same DNA group. The combination of typing profiles allowed two predominant groups (termed A and B) to be distinguished among the A. baumannii isolates (37 and eight isolates, respectively) that shared a specific ribotype and were highly similar in other properties. These two groups comprised both sporadic and outbreak isolates and were found in most localities. Group A and B isolates were markedly more resistant to antibiotics than most of the remaining isolates, thus representing 85% of all multiresistant isolates. The features of groups A and B corresponded to those of two epidemic clones identified recently among hospital strains in north-western Europe. (+info)
Functional evaluation of the genes involved in malonate decarboxylation by Acinetobacter calcoaceticus.
(3/123)
The genomic locus containing the potential repressor gene mdcY (inactivated by a putative IS3 element) and the mdcLMACDEGBH genes from Acinetobacter calcoaceticus was cloned and sequenced. In order to evaluate the biochemical function of the protein components, the genes were expressed independently and their activities predicted by database analysis. The mdcA gene product, the alpha subunit, was found to be malonate/acetyl-CoA transferase and the mdcD gene product, the beta subunit, was found to be malonyl-CoA decarboxylase. The mdcE gene product, the gamma subunit, may play a role in subunit interaction to form a stable complex or as a codecarboxylase. The mdcC gene product, the delta subunit, was an acyl-carrier protein, which has a unique CoA-like prosthetic group. Various combinations of malonate decarboxylase subunits allowed us to estimate their contribution to malonyl-CoA decarboxylase activity. The prosthetic group was identified as carboxymethylated 2'-(5"-phosphoribosyl)-3'-dephospho-CoA by mass spectrometry. The mdcH gene product was determined to have malonyl-CoA/dephospho-CoA acyltransferase activity. Using database analysis mdcLM, mdcG, mdcB and mdcI were estimated to be the genes for a malonate transporter, a holo-acyl carrier synthase, protein for the formation of precursor of the prosthetic group and a regulatory protein, respectively. From the data shown above we propose a metabolic pathway for malonate in A. calcoaceticus. (+info)
Autoantibodies to brain components and antibodies to Acinetobacter calcoaceticus are present in bovine spongiform encephalopathy.
(4/123)
Bovine spongiform encephalopathy (BSE) is a neurological disorder, predominantly of British cattle, which belongs to the group of transmissible spongiform encephalopathies together with Creutzfeldt-Jakob disease (CJD), kuru, and scrapie. Autoantibodies to brain neurofilaments have been previously described in patients with CJD and kuru and in sheep affected by scrapie. Spongiform-like changes have also been observed in chronic experimental allergic encephalomyelitis, at least in rabbits and guinea pigs, and in these conditions autoantibodies to myelin occur. We report here that animals with BSE have elevated levels of immunoglobulin A autoantibodies to brain components, i.e., neurofilaments (P < 0.001) and myelin (P < 0.001), as well as to Acinetobacter calcoaceticus (P < 0.001), saprophytic microbes found in soil which have sequences cross-reacting with bovine neurofilaments and myelin, but there were no antibody elevations against Agrobacterium tumefaciens or Escherichia coli. The relevance of such mucosal autoantibodies or antibacterial antibodies to the pathology of BSE and its possible link to prions requires further evaluation. (+info)
3,4-Dihydrocoumarin hydrolase with haloperoxidase activity from Acinetobacter calcoaceticus F46.
(5/123)
A novel lactonohydrolase, an enzyme that catalyzes the hydrolysis of 3,4-dihydrocoumarin, was purified 375-fold to apparent homogeneity, with a 22.7% overall recovery, from Acinetobacter calcoaceticus F46, which was isolated as a fluorene-assimilating micro-organism. The molecular mass of the native enzyme, as estimated by high-performance gel-permeation chromatography, is 56 kDa, and the subunit molecular mass is 30 kDa. The enzyme specifically hydrolyzes 3,4-dihydrocoumarin, and the Km and Vmax for 3,4-dihydrocoumarin are 0.806 mM and 4760 U.mg-1, respectively. The N-terminal and internal amino acid sequences of the enzyme show high similarity to those of bacterial non-heme haloperoxidases. The enzyme exhibits brominating activity with monochlorodimedon in the presence of H2O2 and 3, 4-dihydrocoumarin or an organic acid, such as acetate and n-butyrate. (+info)
ComP, a pilin-like protein essential for natural competence in Acinetobacter sp. Strain BD413: regulation, modification, and cellular localization.
(6/123)
We recently identified a pilin-like competence factor, ComP, which is essential for natural transformation of the gram-negative soil bacterium Acinetobacter sp. strain BD413. Here we demonstrate that transcription and synthesis of the pilin-like competence factor ComP are maximal in the late stationary growth phase, whereas competence is induced immediately after inoculation of a stationary-phase culture into fresh medium. Western blot analyses revealed three forms of ComP, one with an apparent molecular mass of 15 kDa, which correlates with the molecular mass deduced from the DNA sequence, one 20-kDa form, which was found to be glycosylated, and one 23-kDa form. The glycosylation of ComP was not required for its function in DNA binding and uptake. The 20-kDa form was present in the cytoplasmic membrane, the periplasm, and the outer membrane, whereas the 23-kDa form was located in the outer membrane and might be due to a further modification. Immunological data suggest that ComP is not a subunit of the pilus structures. Possible functions of ComP in the DNA transformation machinery of Acinetobacter sp. strain BD413 are discussed. (+info)
The malonate decarboxylase operon of Acinetobacter calcoaceticus KCCM 40902 is regulated by malonate and the transcriptional repressor MdcY.
(7/123)
A regulatory gene-like open reading frame oriented oppositely to mdcL, coined mdcY, was found upstream from the structural genes of the mdcLMACDEGBH operon in Acinetobacter calcoaceticus KCCM 40902. To elucidate the function of this gene, mdcY was expressed in Escherichia coli, and the MdcY protein was purified to homogeneity. Its DNA binding activity and binding site were examined by gel retardation and footprinting assays in vitro and by site-directed mutagenesis of the binding sites in vivo. The regulator bound target DNA regardless of the presence of malonate, and the binding site was found centered at -65 relative to the mdcL transcriptional start site and contains a 12-bp palindromic structure (5'-ATTGTA/TACAAT-3'). Using a promoter fusion to the reporter gene luc, we found that the promoter P(mdcY) is negatively regulated by MdcY independent of malonate. However, the promoter P(mdcL) recovered its activity in the presence of malonate. When mdcY was introduced into A. calcoaceticus KCCM 40902 in which the gene is inactivated by an IS3 family element, malonate decarboxylase was significantly repressed in cultures growing in acetate, succinate, or Luria-Bertani medium. However, in cells growing in malonate, malonate decarboxylase was induced, indicating that MdcY is a transcriptional repressor and that malonate or a product resulting from malonate metabolism should be the intracellular inducer of the mdc operon. (+info)
Ca(2+) stabilizes the semiquinone radical of pyrroloquinoline quinone.
(8/123)
Spectroelectrochemical studies were performed on the interaction between Ca(2+) and pyrroloquinoline quinone (PQQ) in soluble glucose dehydrogenase (sGDH) and in the free state by applying a mediated continuous-flow column electrolytic spectroelectrochemical technique. The enzyme forms used were holo-sGDH (the holo-form of sGDH from Acinetobacter calcoaceticus) and an incompletely reconstituted form of this, holo-X, in which the PQQ-activating Ca(2+) is lacking. The spectroelectrochemical and ESR data clearly demonstrated the generation of the semiquinone radical of PQQ in holo-sGDH and in the free state in the presence of Ca(2+). In contrast, in the absence of Ca(2+) no semiquinone was observed, either for PQQ in the free state (at pH 7.0) or in the enzyme (holo-X). Incorporation of Ca(2+) into the active site of holo-X, yielding holo-sGDH, caused not only stabilization of the semiquinone form of PQQ but also a negative shift (of 26.5 mV) of the two-electron redox potential, indicating that the effect of Ca(2+) is stronger on the oxidized than on the reduced PQQ. Combining these data with the observations on the kinetic and chemical mechanisms, it was concluded that the strong stimulating effect of Ca(2+) on the activity of sGDH can be attributed to facilitation of certain kinetic steps, and not to improvement of the thermodynamics of substrate oxidation. The consequences of this conclusion are discussed for the oxidative as well as for the reductive part of the reaction of sGDH. (+info)