Reclassification of Brevibacterium oxydans (Chatelain and Second 1966) as Microbacterium oxydans comb. nov.
Phylogenetic and chemotaxonomic analyses indicate that Brevibacterium oxydans is closely related to species of the genus Microbacterium, namely Microbacterium liquefaciens, Microbacterium luteolum and Microbacterium saperdae. DNA-DNA reassociation values of less than 60% between Brevibacterium oxydans and these three Microbacterium species support the distinctness of this misclassified Brevibacterium species, which is reclassified as Microbacterium oxydans comb. nov. (+info
Reclassification of Brevibacterium incertum (Breed 1953) as Desemzia incerta gen. nov., comb. nov.
Phylogenetic analysis of 16S rDNA indicates that Brevibacterium incertum is not a member of the genus Brevibacterium but related to species of the genus Carnobacterium. Hence, Brevibacterium incertum is not a member of the class Actinobacteria but belongs to the phylogenetically defined broad Bacillus-Lactobacillus cluster. Based upon properties that taxonomically clearly distinguishes Brevibacterium incertum from species of the phylogenetic sister genus Carnobacterium, Brevibacterium incertum is reclassified as Desemzia incerta gen. nov., comb. nov. (+info
Structure and organization of the rrnD operon of 'Brevibacterium lactofermentum': analysis of the 16S rRNA gene.
Five rRNA operons (rrn) were found by hybridization in the genome of 'Brevibacterium lactofermentum' ATCC 13869 and Corynebacterium glutamicum ATCC 13032. 'B. lactofermentum' DSM 20412 differed from the other corynebacteria tested in showing six hybridizing BamHI bands. Two of the rrn operons (rrnD and rrnE) were located in a single cosmid. Sequencing of the rrnD operon showed that it contains a complete 16S rRNA-23S RNA-5S rRNA gene cluster. Phylogenetic studies using the complete 16S rRNA sequence showed that 'B. lactofermentum' is closely related to several species of the genus Corynebacterium but only distantly related to the type species Brevibacterium linens and the authors suggest that it should be reclassified as Corynebacterium lactofermentum. The 5' end of mature 16S rRNA was identified by primer extension. Sequence elements similar to those of mycobacteria implicated in transcription antitermination (Boxes A, B, C) and in processing of the pre-rRNA to 16S rRNA were identified. An open reading frame encoding an rpoD-like sigma factor (named SigC) different from the previously reported SigA and SigB proteins was found upstream of rrnD in the opposite orientation. Both rpoD and sigC seem to be expressed from a bidirectional promoter region. (+info
Biodegradation of cyclohexylamine by Brevibacterium oxydans IH-35A.
A bacterial strain capable of growing on cyclohexylamine (CHAM) was isolated by using enrichment and isolation techniques. The strain isolated, strain IH-35A, was classified as a member of the genus Brevibacterium. The results of growth and enzyme studies are consistent with degradation of CHAM via cyclohexanone (CHnone), 6-hexanolactone, 6-hydroxyhexanoate, and adipate. Cell extracts obtained from this strain grown on CHAM contained CHAM oxidase, and the model for CHAM oxidation by this enzyme was similar to the model for deamino oxidation of amine by amine oxidase. (+info
A new carboxylesterase from Brevibacterium linens IFO 12171 responsible for the conversion of 1,4-butanediol diacrylate to 4-hydroxybutyl acrylate: purification, characterization, gene cloning, and gene expression in Escherichia coli.
A carboxylesterase that is responsible for conversion of 1,4-butanediol diacrylate (BDA) to 4-hydroxybutyl acrylate (4HBA) was found in Brevibacterium lines IFO 12171, and purified to homogeneity. The purified enzyme was active toward a variety of diesters of ethylene glycol, 1,4-butanediol, and 1,6-hexanediol. The K(m) and kcat of the enzyme for BDA were 3.04 mM and 203,000 s-1, respectively. The reaction with the purified enzyme gave 98 mM 4HBA from 100 mM BDA for 60 min. The enzyme gene was cloned from the chromosomal DNA of the bacterium. The open reading frame encoding the enzyme was 1176 bp long, corresponding to a protein of 393 amino acid residues (molecular mass = 42,569 Da). The deduced amino acid sequence contained the tetra peptide motif sequence, STTK, and the serine residue was confirmed to be the catalytic center of BDA esterase by site-directed mutagenesis for several amino acid residues. The gene was expressed in Escherichia coli under the control of the lac promoter, and the gene product (a fusion protein with 6 amino acid residues from beta-galactosidase) showed the same catalytic properties as the enzyme from the parent strain. (+info
In-vitro activity of levofloxacin, ofloxacin and D-ofloxacin against coryneform bacteria and Listeria monocytogenes.
The objective of this study was to evaluate the in-vitro activity of levofloxacin, ofloxacin and D-ofloxacin compared with ciprofloxacin, norfloxacin and sparfloxacin against coryneform bacteria and Listeria monocytogenes isolated from clinical samples. The following organisms (and number of strains) were studied: Corynebacterium jeikeium (20), Corynebacterium urealyticum (20), Corynebacterium minutissimum (20), Corynebacterium striatum (20), Corynebacterium amycolatum (30), Brevibacterium spp. (15) and Listeria monocytogenes (15). Antimicrobial activity was determined by microdilution using cation-adjusted Mueller-Hinton broth supplemented with 0.5% Tween 80 when testing C. jeikeium or C. urealyticum. Fluoroquinolones were used in the range 0.015-16 mg/L. Plates were incubated in air at 35 degrees C for 18-20 h (24 h when testing C. jeikeium or C. urealyticum). The following MIC50 values were obtained for all 140 organisms tested: levofloxacin, 1 mg/L; ofloxacin, 2 mg/L; D-ofloxacin, > 16 mg/L; ciprofloxacin, 1 mg/L; norfloxacin, 16 mg/L; sparfloxacin, 1 mg/L. MIC90 values were > 16 mg/L for all test antibiotics with the exception of levofloxacin, which had an MIC90 value of 16 mg/L. At a concentration of 2 mg/L, levofloxacin inhibited all L. monocytogenes strains and 35-93% of the remaining species. MIC90 values of ofloxacin were one dilution step higher than those of levofloxacin against C. minutissimum, C. striatum, Brevibacterium spp. and L. monocytogenes. Levofloxacin showed similar (C. jeikeium, C. urealyticum, C. amycolatum and Brevibacterium spp.) or greater (C. minutissimum and C. striatum) activity than ciprofloxacin and sparfloxacin, and higher than D-ofloxacin or norfloxacin against all species studied. In conclusion, levofloxacin was the most active of the six fluoroquinolones evaluated against coryneform bacteria isolated from clinical samples and could therefore be a promising treatment option in this setting. (+info
Kinetic mechanisms of cholesterol oxidase from Streptomyces hygroscopicus and Brevibacterium sterolicum.
The kinetic properties of two cholesterol oxidases, one from Brevibacterium sterolicum (BCO) the other from Streptomyces hygroscopicus (SCO) were investigated. BCO works via a ping-pong mechanism, whereas the catalytic pathway of SCO is sequential. The turnover numbers at infinite cholesterol and oxygen concentrations are 202 s-1 and 105 s-1 for SCO and BCO, respectively. The rates of flavin reduction extrapolated to saturating substrate concentration, under anaerobic conditions, are 235 s-1 for BCO and 232 s-1 for SCO (in the presence of 1% Thesit and 10% 2-propanol). With reduced SCO the rate of Delta5-6-->Delta4-5 isomerization of the intermediate 5-cholesten-3-one to final product is slow (0.3 s-1). With oxidized SCO and BCO the rate of isomerization is much faster ( approximately 300 s-1), thus it is not rate-limiting for catalysis. The kinetic behaviour of both reduced COs towards oxygen is unusual in that they exhibit apparent saturation with increasing oxygen concentrations (extrapolated rates approximately 250 s-1 and 1.3 s-1, for BCO and SCO, respectively): too slow to account for catalysis. For BCO the kinetic data are compatible with a step preceding the reaction with oxygen, involving interconversion of reactive and nonreactive forms of the enzyme. We suggest that the presence of micelles in the reaction medium, due to the necessary presence of detergents to solubilize the substrate, influence the availability or reactivity of oxygen towards the enzyme. The rate of re-oxidation of SCO in the presence of product is also too slow to account for catalysis, probably due to the impossibility of producing quantitatively the reduced enzyme-product complexes. (+info
Propeptide of the metalloprotease of Brevibacillus brevis 7882 is a strong inhibitor of the mature enzyme.
A metalloprotease gene of Brevibacillus brevis (npr) was expressed in Escherichia coli in a soluble form as native Npr precursor. A significant fraction of the precursor was spontaneously processed, producing the N-terminal propeptide and the mature enzyme. A strong inhibition of the mature Npr by its own propeptide in the crude lysate was observed even in the absence of the covalent linkage between them. Pure precursor, propeptide and the mature Npr were isolated and kinetic parameters of the mature enzyme inhibition by the propeptide were determined. The inhibition is of the tight-binding competitive type with Ki 0.17 nM. Inhibition of metalloproteases from Brevibacillus megaterium and thermolysine by the heterologous propeptide of the Npr from B. brevis was much weaker or none. (+info