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PubMed2005

Biochemical evidence for the proteolytic degradation of infectious prion protein PrPsc in hamster brain homogenates by foodborne bacteria.

PrP(Sc) is a general term to describe the infectious agent causing transmissible spongiform encephalopathy (TSE), and the protease-resistant form of cellular PrP(C). In this study, we have identified several protease-secreting bacteria able to degrade PrP(Sc) under more or less native conditions (30 degrees C, pH 8), focusing on strains isolated mainly from cheese. One hundred and ninty-nine protease-secreting isolates belonging to the Actinomycetales and Bacillales were screened for the expression of PrP(Sc) degrading activity by a Western blot procedure. Only 6 strains belonging to the following species were found to exhibit such an activity: Arthrobacter nicotianae, Bacillus licheniformis, Brachybacterium conglomeratum, Brachybacterium tyrofermentans and Staphylococcus sciuri and Serratia spp. As revealed by a general protease assay based on dye-labeled Azocoll substrate, the PrP(Sc) degrading activity was not directly correlated to the total level of secreted proteolytic activity of these organisms. This indicates that specific proteases are required for the degradation of PrP(Sc). Our study also suggests the potential use of such starter bacteria or their proteases for application in PrP(Sc) degradation and decontamination under native conditions.

Actinomycetales↗

PubMed2006

Molecular identification and differentiation of Brevibacterium species and strains.

Amplified ribosomal DNA restriction enzyme analysis (ARDRA), pulsed field gel electrophoresis (PFGE) and ribotyping were used to differentiate among 24 strains of Brevibacterium linens, Brevibacterium casei and Brevibacterium epidermidis obtained from type culture collections or isolated from various smear ripened cheeses. ARDRA was applied to the 16S rDNA. B. linens was shown to be a quite heterogenic group with 2 to at least 4 copies of rrn operons per strain with aberrant nucleotide sequences. AccI gave genus specific restriction patterns and was used to separate Brevibacterium from Corynebacterium species. The expected species specificity of TaqI applied to B. linens type culture strains, but not to all strains isolated from cheese. By AvaI restriction, B. casei and B. linens were differentiated from B. epidermidis and the orange pigmented Arthrobacter casei, a new species of coryneform bacteria; by XmnI restriction, B. linens and B. epidermidis were differentiated from B. casei. One of 4 B. linens genotypes could not be distinguished from B. casei by this method. Here, the typical orange B. linens pigments were used for classification, which was confirmed by partial sequencing of the 16S rDNA.

Arthrobacter↗

PubMed1981

2,3-Dehydro-4-epi-N-acetylneuraminic acid; a neuraminidase inhibitor.

Treatment of N-acetylneuraminic acid methyl ester with sulfuric acid and acetic anhydride at 50 degrees followed by deacetylation gave 2,3-dehydro-2-deoxy-N-acetylneuraminic acid methyl ester and methyl 5-acetamido-2,6-anhydro-2,3,5-trideoxy-D-glycero-D-talo-non-2-enonate (2,3-dehydro-4-epi-NeuAc methyl ester) in equal yields (approximately 40% each). The structure of the latter was ascertained primarily from analysis of its mass spectrum and 1H- and 13C-nuclear magnetic resonance spectra. The relative proportions of these two glycals in the foregoing reaction was dependent on temperature, as at 0 degrees, the yield of 2,3-dehydro-4-epi-NeuAc was markedly diminished. A minor by-product of this acetylation reaction was 2-methyl-(methyl 7,8,9-tri-O-acetyl-2,6-anhydro-2,3,5-trideoxy-D-glycero-D-talo-non-2-enonate)-[ 4,5-d]-2-oxazoline. Based upon this finding and additional interconversion experiments, a mechanism involving the intermediacy of the latter oxazoline to account for the epimerization is proposed. These glycals and their methyl esters are competitive inhibitors of Arthrobacter sialophilus, neuraminidase, suggesting that the 4-hydroxyl group must be equatorially oriented for maximal enzyme inhibition.

Arthrobacter↗

PubMed1975

The fine structure of the branched alpha-D-glucan from the blue-green alga Anacystis nidulans: comparison with other bacterial glycogens and phytoglycogen.

The fine structure of the glycogen from the blue-green alga Anacystis nidulans has been examined. After selective hydrolysis of all (1 yields 6)-alpha-D linkages by a bacterial isoamylase, the resulting mixture of linear chains was subjected to gel permeation chromatography. For purposes of comparison, the glycogens from Escherichia coli and Arthrobacter sp., amylopectin, phytoglycogen from sweet corn, and shell-fish glycogen were treated similarly. The profiles of the unit chains of A nidulans glycogen and phytoglycogen were closely similar. There was no close resemblance in the size distribution of unit chains for A. nidulans glycogen, other bacterial glycogens, and amylopectin.

Amylases↗

PubMed2001

Biological elimination of H2S and NH3 from wastegases by biofilter packed with immobilized heterotrophic bacteria.

Biotreatment of various ratios of H2S and NH3 gas mixtures was studied using the biofilters, packed with co-immobilized cells (Arthrobacter oxydans CH8 for NH3 and Pseudomonas putida CH11 for H2S). Extensive tests to determine removal characteristics, removal efficiency, removal kinetics, and pressure drops of the biofilters were performed. To estimate the largest allowable inlet concentration, a prediction model was also employed. Greater than 95%, and 90% removal efficiencies were observed for NH3 and H2S, respectively, irrespective of the ratios of H2S and NH3 gas mixtures. The results showed that H2S removal of the biofilter was significantly affected by high inlet concentrations of H2S and NH3. As high H2S concentration was an inhibitory substrate for the growth of heterotrophic sulfur-oxidizing bacteria, the activity of H2S oxidation was thus inhibited. In the case of high NH3 concentration, the poor H2S removal efficiency might be attributed to the acidification of the biofilter. The phenomenon was caused by acidic metabolite accumulation of NH3. Through kinetic analysis, the presence of NH3 did not hinder the NH3 removal, but a high H2S concentration would result in low removal efficiency. Conversely, H2S of adequate concentrations would favor the removal of incoming NH3. The results also indicated that maximum inlet concentrations (model-estimated) agreed well with the experimental values for space velocities of 50-150 h(-1). Hence, the results would be used as the guideline for the design and operation of biofilters.

Air Pollution↗

PubMed1998

Asking for the indicator function of bioassays evaluating soil contamination: are bioassay results reasonable surrogates of effects on soil microflora?

In evaluating the biological effect of solid materials like soil a bacterial contact assay often shows higher sensitivity than elutriate testing. Results of the Bacillus cereus contact assay for some environmental important toxicants are presented in this article. A comparison with another heterotrophic soil bacterium, Arthrobacter globiformis, shows comparable sensitivity. In a bioassay approach organisms at the level of individuals or populations are exposed to soil material to determine the significance of contaminants. An investigation that incorporates community level processes in comparison with toxicity test results provides a better understanding of the indicator function of bioassays. Comparison of soil bioassays (aqueous and solid phase) with ecological parameters demonstrates the problems in predicting ecological effects of soil contamination.

Arthrobacter↗

PubMed1999

Specific detection of p-chlorobenzoic acid by Escherichia coli bearing a plasmid-borne fcbA'::lux fusion.

In this communication we report on a genetically engineered bacterium that reacts by light emission to the presence of 4-chlorobenzoic acid. To construct this strain, DNA fragment (1.7 kb) upstream from the 4-chlorobenzoic acid dehalogenase (fcb) operon of Arthrobacter SU was fused to Vibriofischeri luxCDABE genes. An Escherichia coli strain transformed with a multi-copy plasmid (pASU) bearing this fusion responded to the presence of 4-chlorobenzoic acid and a few closely related compounds by increased luminescence, exhibiting a high specificity but a relatively low sensitivity. While it could be somewhat, improved by manipulating the experimental pH, sensitivity remained too low for real time applicability. Nevertheless, the principle of using dehalogenase promoters as environmental pollution sensor was demonstrated.

Arthrobacter↗

PubMed2001

Enzyme activity determination on macromolecular substrates by isothermal titration calorimetry: application to mesophilic and psychrophilic chitinases.

Isothermal titration calorimetry has been applied to the determination of the kinetic parameters of chitinases (EC 3.2.1.14) by monitoring the heat released during the hydrolysis of chitin glycosidic bonds. Experiments were carried out using two different macromolecular substrates: a soluble polymer of N-acetylglucosamine and the insoluble chitin from crab shells. Different experimental temperatures were used in order to compare the thermodependence of the activity of two chitinases from the psychrophile Arthrobacter sp. TAD20 and of chitinase A from the mesophile Serratia marcescens. The method allowed to determine unequivocally the catalytic rate constant k(cat), the activation energy (E(a)) and the thermodynamic activation parameters (DeltaG(#), DeltaH(#), DeltaS(#)) of the chitinolytic reaction on the soluble substrate. The catalytic activity has also been determined on insoluble chitin, which displays an effect of substrate saturation by chitinases. On both substrates, the thermodependence of the activity of the psychrophilic chitinases was lower than that observed with the mesophilic counterpart.

Arthrobacter↗

PubMed1999

Fractal analysis to discriminate between biotic and abiotic attacks on chalcopyrite and pyrolusite.

In the present paper, a model describing release and mobility of copper and manganese in chalcopyrite and pyrolusite powders due to bacterial bioleaching, i.e. Thiobacillus ferrooxidans and Arthrobacter sp., is proposed. Sites where copper and manganese were released were examined by scanning electron microscopy (SEM). The resulting micrographs were scanned and submitted to a point by point fractal analysis to verify if a discrimination between biological and chemical attack could be established on the basis of the distribution of the fractional part of the fractal dimension over the whole surface. We demonstrate that such a method is able to discriminate among the different attacks.

Arthrobacter↗

PubMed1999

Assessment of bacterial community structure in soil by polymerase chain reaction and denaturing gradient gel electrophoresis.

Bacterial community structure was studied in a Flevo silt loam (FSL) soil microplot, as well as in 15 other soils, by using DNA extraction followed by molecular fingerprinting. Total community DNA was extracted and purified by a direct method, which yielded amplifiable DNA of high molecular weight for all soils. A variable region of the 16S rRNA gene was then amplified by PCR with bacterial primers, resulting in a mixture of amplicons separable via denaturing gradient gel electrophoresis (DGGE). The DGGE profiles of FSL soil were indicative of dominant soil bacterial types, as evidenced by assessing the amplification of Enterobacter cloacae and Arthrobacter sp. targets in a soil DNA background. These targets produced barely detectable bands when present in soil DNA at roughly 5 x 10(6) genome equivalents per g dry soil, and strong bands at 27-fold higher levels. The PCR-DGGE analysis of the FSL soil was highly reproducible. Furthermore, different single versus composite topsoil samples yielded similar DGGE profiles with respect to major bands. In addition, samples taken along vertical soil cores (0-45 cm depth) revealed relative stability of the DGGE profiles. The profiles produced with DNA obtained from different aggregate size fractions of this soil were also similar with respect to the main bands. Moreover, FSL topsoil samples taken over a 1-year period (fallow soil) yielded stable profiles. These data suggested that the soil bacterial communities thus determined were dominated by a limited number of stable and ubiquitous types. The 16 soils, representing varying types and geographical locations, were assessed for differences in their bacterial DGGE profiles. There were striking differences between the profiles obtained for these soils. Evidence was found for the hypothesis that similar soil types tend to contain similar structures of the dominating bacterial types as revealed by the DGGE profiles.

Arthrobacter↗

PubMed1999

Analysis of the bacterial surface ripening flora of German and French smeared cheeses with respect to their anti-listerial potential.

The anti-listerial potential of 19 different French smeared cheese bacterial consortia was analyzed semi-quantitatively. Comparison of the total viable cell count to the direct microscopic count yielded no indication that non-culturable bacteria contribute significantly to the undefined, complex ripening floras. From 2613 isolates, 48 showed clear inhibition of one or more Listeria monocytogenes strains on solid medium, while only three isolates excreted an anti-listerial, soluble substance when grown in liquid culture. From a total of 299 strains isolated from German dairy products, 30 strains inhibited at least one L. monocytogenes indicator strain on solid medium. Bacteria with antilisterial potential were members of the genera Arthrobacter, Brevibacterium, Corynebacterium, Enterococcus, Micrococcus and Microbacterium. Cluster analysis of inhibition pattern revealed that similar anti-listerial substances are produced by species belonging to different genera. Half of the strains inhibited six or more out of 12 Listeria indicator strains and are promising candidates for the development of a defined red smear cheese ripening flora. L. monocytogenes originating from red-smear cheese had a tendency to be more resistant towards anti-listerial activity than those isolated from other sources.

Animals↗

PubMedDate not supplied

Inhibition of copper amine oxidases by pyridine-derived aldoximes and ketoximes.

The reactions of pea diamine oxidase (PSAO) and 2-phenylethylamine oxidase from Arthrobacter globiformis (AGAO) with pyridine-derived oximes were studied. Pyridine carbaldoximes and alkyl pyridyl ketoximes act as strong non-competitive inhibitors of the enzymes. The inhibition constants K(i) of these compounds vary between 10(-4) and 10(-5) M, for AGAO and some of the studied oximes were found even micromolar K(i) values. The presence of pyridine moiety in the studied compounds has remarkable influence on the inhibition potency. Elementary oximes lacking the heterocyclic ring, i.e., aliphatic (acetone oxime), alicyclic (cyclohexanone oxime) and aromatic (benzaldoxime), are considerably weaker non-competitive inhibitors (K(i) similar to 10(-3) or 10(-2) M). The position of the pyridine ring substitution by -C(R)=NOH group does not play a significant role for the inhibition potency of the studied oxime compounds. If the pyridine nitrogen is quaternised (in hydroxyiminomethyl-1-methylpyridinium iodides), the compound looses its inhibitory properties. Extended length of alkyl substituents on the ketoxime group of alkyl pyridyl ketoximes increases the K(i) value. The enzyme-bound copper represents one of possible target sites for pyridine-derived oxime inhibitors. The addition of an alkyl pyridyl ketoxime or a pyridine carbaldoxime to a native PSAO sample perturbs the absorption spectrum of the enzyme (by an absorption increase in the region 300-400 nm) that is not observed in the spectrum of reacted PSAO apoenzyme. However, an additional formation of hydrogen bonds with amino acid side-chains at the active site should be considered, namely for 3- and 4-substituted pyridine derivatives.

Amine Oxidase (Copper-Containing)↗

PubMed1997

Classification of catechol 1,2-dioxygenase family: sequence analysis of a gene for the catechol 1,2-dioxygenase showing high specificity for methylcatechols from Gram+ aniline-assimilating Rhodococcus erythropolis AN-13.

Gram+ aniline-assimilating Rhodococcus erythropolis AN-13 (AN-13) produces catechol 1,2-dioxygenase (C12O) showing high enzymatic activities for 3- and 4-methylcatechols [Aoki et al. (1984) Agric. Biol. Chem. 48, 2087-2095]. A 3.0 kb Sau3AI fragment carrying a gene encoding C12O(catA) was cloned by selection of transformants showing C12O activity from a gene library of AN-13. Furthermore, we specified a 1.6 kb SalI fragment containing catA from the Sau3AI fragment by subcloning. Sequence analysis revealed that the 1.6 kb SalI fragment carried a 855 bp open reading frame (ORF) encoding the entire AN-13 catA, preceded by a potential ribosome binding site (RBS). From comparison of the deduced amino acid (aa) sequence of C12O from AN-13 with other C12O reported previously, it was found that the AN-13 enzyme shares 56.0% aa sequence identity with C12o from Arthrobacter sp. mA3 (mA3) [Eck and Belter (1991) Gene 123, 87-92] compared with less than 36.4% aa sequence identities with others. In conclusion, we classified all C12O including the AN-13 enzyme into three subfamilies on the basis of similarity of aa sequences, numbers of aa residues, and substrate specificity.

Amino Acid Sequence↗

PubMed2003

Process for producing the potential food ingredient DFA III from inulin: screening, genetic engineering, fermentation and immobilisation of inulase II.

Difructose anhydride (DFA III) is a new potential sweet food additive. A screening was undertaken to isolate bacterial strains for conversion of inulin to DFA. Of special interest were thermotolerant enzymes. Some 400 strains were investigated, among four of them produce DFA and strain Buo141 expresses an extracellular enzyme which is stable at elevated temperatures. Based on metabolic data and 16S-rRNA-sequencing, the strain was identified as a new Arthrobacter species. For increased enzyme production, the inulase gene was cloned into E. coli XL1-blue, inulase II was expressed and its activity detected. After identifying the cleavage site, the sequence coding for a signal-peptide was eliminated from the plasmid and a beneficial amino acid exchange introduced by error-prone PCR. The recombinant E. coli was fermented to 10.5 g/l and after disruption an activity of 1.76 MioU/l was observed. The enzyme was flocculated from supernatant and entrapped in calcium alginate hydrogels. To enable production of uniform and small beads JetCutter technology was used with a production rate of 5600 beads/(snozzle). The influence of bead diameter on activity was investigated. An activity of 196 U/g was measured for 600-microm beads.

Amino Acid Substitution↗

PubMed1998

Cloning and sequence determination of a phi AAU2 gene whose product aborts the phage lytic cycle.

This communication describes the cloning of a 1.8-kb fragment from the genome of the corynephage phi AAU2, which aborts the phage lytic cycle when cloned on a high-copy shuttle vector. The associated phenotype, called Apld (aborting phage lytic development), was revealed by noting the reduced plaque size and lower efficiencies of plaquing of phi AAU2 cp, a virulent derivative of phi AAU2, on "Arthrobacter aureus"-C70 Apld+ cells. Adsorption and phage DNA transfection experiments showed evidence that Apld acted once the phage DNA had entered into the cell; apld was confined to a single open reading frame (ORF), encoding a putative 63-aa polypeptide which did not show any homology to proteins contained in the databanks; apld is followed by an ORF the product of which shows homology with a protein expressed by the early region of the Streptomyces phage phi C31.

Amino Acid Sequence↗

PubMed2000

Effect of associative bacteria on element composition of barley seedlings grown in solution culture at toxic cadmium concentrations.

The response of barley seedlings to inoculation with associative rhizobacteria Azospirillum lipoferum 137, Arthrobacter mysorens 7, Agrobacterium radiobacter 10 and Flavobacterium sp. L30 was studied in hydroponic and quartz sand cultures in the presence of 50 microM CdCl2. Cadmium caused severe inhibition in the growth and uptake of nutrient elements by the plants. Inoculation with the bacteria slightly stimulated root length and biomass of hydroponically grown Cd-treated seedlings. The bacteria increased the content of nutrients such as P, Mg, Ca, Fe, Mn and Na in roots and or shoots of the plants grown in the absence of Cd. Positive changes in the element composition caused by the bacteria were less pronounced in Cd-treated plants, whereas the total amount of nutrients taken by the inoculated plants was generally increased significantly. The content of Cd in the inoculated plants was unchanged, except increased in roots upon addition of A. lipoferum 137. Inoculation did not affect the activity of peroxidase, alpha-mannosidase, phosphodiesterae, alpha-galactosidase, and concentration of sulfhydryl compounds used as biochemical markers of stress in plant roots. The results showed that associative bacteria were capable of decreasing partially the toxicity of Cd for the barley plants through the improvement in uptake of nutrient elements.

Arthrobacter↗

PubMed2002

Conversion of liposomal 4-androsten-3,17-dione by A. simplex immobilized cells in calcium pectate.

Arthrobacter simplex ATCC 6946 free and immobilized cells were assayed for their ability to convert 4-androsten-3,17-dione (AD) to 1,4-androstadien-3,17-dione (ADD) in aqueous and liposomal media. Bioconversions were carried out in a 100 ml flask containing 25 ml of AD liposomal or aqueous medium for 3h, and AD concentrations ranging from 0.3 to 1.0 mM were tested. AD/ADD ratios in samples were determined by HPLC. Biotransformation of substrate entrapped in multilamellar vesicles (MLV) was demonstrated to be better than the corresponding free form. In the former case, 2h were necessary to completely bioconvert 1 mM AD. By contrast, 3h were needed to reach 50% bioconversion in (4%) ethanol medium containing 0.63 mM AD. The liposomal medium allows us to perform steroid conversions at high concentrations of AD, reusing immobilized cells in suitable conditions which are non-toxic for microorganisms.

Androstenedione↗

PubMed1998

The 1.8 A crystal structure of the ycaC gene product from Escherichia coli reveals an octameric hydrolase of unknown specificity.

BACKGROUND: The ycaC gene comprises a 621 base pair open reading frame in Escherichia coli. The ycaC gene product (ycaCgp) is uncharacterized and has no assigned function. The closest sequence homologs with an assigned function belong to a family of bacterial hydrolases that catalyze isochorismatase-like reactions, but these have only low sequence similarity to ycaCgp (approximately 20% amino acid identity). The ycaCgp was obtained and identified during crystallization trials of an unrelated E. coli protein with which it co-purified. RESULTS: The 1.8 A crystal structure of ycaCgp reveals an octameric complex comprised of two tetrameric rings. A large three-layer (alphabetaalpha) sandwich domain and a small helical domain form the folded structure of the monomeric unit. Comparisons with sequence and structure databases suggest that ycaCgp belongs to a diverse family of bacterial hydrolases. The most closely related three-dimensional structure is that of the D2 tetrameric N-carbamoylsarcosine amidohydrolase (CSHase) from an Arthrobacter species. A conspicuous cleft between two ycaCgp subunits contains several conserved residues including Cys118, which we propose to be catalytic. In the active site, a nonprolyl cis peptide bond precedes Val114 and coincides with a cis peptide bond in CSHase in a region of dissimilar sequence. The crystal structure reveals a probable error or mutation relative to the reported genomic sequence. CONCLUSIONS: Although the specific function of ycaCgp is not yet known, structural studies solidify the relationship of this protein to other hydrolases and illuminate its active site and key elements of the catalytic mechanism.

Amidohydrolases↗