The actinobacterial WhiB-like (Wbl) family of transcription factors.

The WhiB-like (Wbl) family of proteins are exclusively found in Actinobacteria. Wbls have been shown to play key roles in virulence and antibiotic resistance in Mycobacteria and Corynebacteria, reflecting their importance during infection by the human pathogens Mycobacterium tuberculosis, Mycobacterium leprae and Corynebacterium diphtheriae. In the antibiotic-producing Streptomyces, several Wbls have important roles in the regulation of morphological differentiation, including WhiB, a protein that controls the initiation of sporulation septation and the founding member of the Wbl family. In recent years, genome sequencing has revealed the prevalence of Wbl paralogues in species throughout the Actinobacteria. Wbl proteins are small (generally ~80-140 residues) and each contains four invariant cysteine residues that bind an O2 - and NO-sensitive [4Fe-4S] cluster, raising the question as to how they can maintain distinct cellular functions within a given species. Despite their discovery over 25 years ago, the Wbl protein family has largely remained enigmatic. Here I summarise recent research in Mycobacteria, Corynebacteria and Streptomyces that sheds light on the biochemical function of Wbls as transcription factors and as potential sensors of O2 and NO. I suggest that Wbl evolution has created diversity in protein-protein interactions, [4Fe-4S] cluster-sensitivity and the ability to bind DNA.

Characterization of some bacterial strains isolated from animal clinical materials and identified as Corynebacterium xerosis by molecular biological techniques.

Eighteen Corynebacterium xerosis strains isolated from different animal clinical specimens were subjected to phenotypic and molecular genetic studies. On the basis of the results of the biochemical characterization, the strains were tentatively identified as C. xerosis. Phylogenetic analysis based on comparative analysis of the sequences of 16S rRNA and rpoB genes revealed that the 18 strains were highly related to C. xerosis, C. amycolatum, C. freneyi, and C. hansenii. There was a good concordance between 16S rRNA and partial rpoB gene sequencing results, although partial rpoB gene sequencing allowed better differentiation of C. xerosis. Alternatively, C. xerosis was also differentiated from C. freneyi and C. amycolatum by restriction fragment length polymorphism analysis of the 16S-23S rRNA gene intergenic spacer region. Phenotypic characterization indicated that besides acid production from D-turanose and 5-ketogluconate, 90% of the strains were able to reduce nitrate. The absence of the fatty acids C(14:0), C(15:0), C(16:1)omega 7c, and C(17:1)omega 8c can also facilitate the differentiation of C. xerosis from closely related species. The results of the present investigation demonstrated that for reliable identification of C. xerosis strains from clinical samples, a combination of phenotypic and molecular-biology-based identification techniques is necessary.

Corynebacterium sputi sp. nov., isolated from the sputum of a patient with pneumonia.

A coryneform bacterium isolated from the sputum of a patient with pneumonia was characterized by phenotypic and molecular taxonomic methods. Chemotaxonomic investigations revealed the presence of cell-wall chemotype IV and short chain mycolic acids consistent with the genus Corynebacterium. Comparative 16S rRNA gene sequencing studies confirmed this assignment, with the organism forming a hitherto unknown subline within the genus associated with a subcluster containing Corynebacterium hansenii, Corynebacterium freneyi, Corynebacterium xerosis, Corynebacterium amycolatum and Corynebacterium sphenisci. Sequence divergence values of >2.7 % from established corynebacterial species suggested that the new isolate represented a novel species. This was also supported by the results of the biochemical tests. On the basis of phenotypic and phylogenetic evidence, it is proposed that the unknown bacterium be classified as a novel species of the genus Corynebacterium, Corynebacterium sputi sp. nov. (type strain IMMIB L-999(T)=DSM 45148(T)=CCUG 55795(T)).

Sources of the adventitious microflora of a smear-ripened cheese.

AIMS: To determine the relationships between the major organisms from the cheese-making personnel and environment and the surface of a smear cheese. METHODS AND RESULTS: 360 yeast and 593 bacteria from the cheese surface, the dairy environment and the hands and arms of personnel were collected. Pulsed-field gel electrophoresis, repetitive sequence-based polymerase chain reaction and 16S rDNA sequencing were used for typing and identifying the bacteria, and mitochondrial DNA restriction fragment length polymorphism and Fourier-transform infrared spectroscopy for typing and identifying the yeast. The three most dominant bacteria were Corynebacterium casei, Corynebacterium variabile and Staphylococcus saprophyticus, which were divided into three, five and seven clusters, respectively, by macrorestriction analysis. The same clones from these organisms were isolated on the cheese surface, the dairy environment and the skin of the cheese personnel. Debaryomyces hansenii was the most dominant yeast. CONCLUSIONS: A 'house' microflora exists in the cheese plant. Although the original source of the micro-organisms was not identified, the brines were an important source of S. saprophyticus and D. hansenii and, additionally, the arms and hands of the workers the sources of C. casei and C. variabile. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first time that the major contribution of the house microflora to the ripening of a smear-ripened cheese has been demonstrated.

A polyketide synthase catalyzes the last condensation step of mycolic acid biosynthesis in mycobacteria and related organisms.

Mycolic acids are major and specific constituents of the cell envelope of Corynebacterineae, a suborder of bacterial species including several important human pathogens such as Mycobacterium tuberculosis, Mycobacterium leprae, or Corynebacterium diphtheriae. These long-chain fatty acids are involved in the unusual architecture and impermeability of the cell envelope of these bacteria. The condensase, the enzyme responsible for the final condensation step in mycolic acid biosynthesis, has remained an enigma for decades. By in silico analysis of various mycobacterial genomes, we identified a candidate enzyme, Pks13, that contains the four catalytic domains required for the condensation reaction. Orthologs of this enzyme were found in other Corynebacterineae species. A Corynebacterium glutamicum strain with a deletion in the pks13 gene was shown to be deficient in mycolic acid production whereas it was able to produce the fatty acids precursors. This mutant strain displayed an altered cell envelope structure. We showed that the pks13 gene was essential for the survival of Mycobacterium smegmatis. A conditional M. smegmatis mutant carrying its only copy of pks13 on a thermosensitive plasmid exhibited mycolic acid biosynthesis defect if grown at nonpermissive temperature. These results indicate that Pks13 is the condensase, a promising target for the development of new antimicrobial drugs against Corynebacterineae.

A Corynebacterium glutamicum gene encoding a two-domain protein similar to biotin carboxylases and biotin-carboxyl-carrier proteins.

Following the analysis of transposon Tn5432-induced mutants of Corynebacterium glutamicum ATCC 13032, a gene encoding a protein with a biotin-binding motif was cloned. The DNA sequence of this gene revealed an open reading frame encoding 591 amino acids with a calculated mol. mass of 63.4 kDa. The protein is composed of two domains, an N-terminal biotin carboxylase and a C-terminal biotin-carboxyl-carrier protein, that are highly similar to corresponding subunits from prokaryotic and eukaryotic biotin enzymes. Over 70% identity was found to a protein from Mycobacterium leprae proposed to be part of an acyl-CoA carboxylase. Since it was not possible to inactivate the C. glutamicum gene, the gene most likely encodes a subunit of the essential acetyl-CoA carboxylase, which catalyzes the committed step in fatty acid synthesis.

Size and homology of the genomes of leprosy-derived corynebacteria, Mycobacterium leprae, and other corynebacteria and mycobacteria.

The genomes of Mycobacterium leprae and leprosy-derived corynebacteria (LDC), which have a similar base composition of guanine + cytosine 56 mol %, have been compared with those of reference bacteria of the CMN group (genera Corynebacterium, Mycobacterium, Nocardia). Genome sizes of three LDC strains were (1.2-2.5) x 10(6) base pairs. DNA from four of seven LDC strains examined had homology levels greater than 60%. Two other strains had a homology of 40% when compared with the CMN strains and one strain was distinctly different. The DNA from all seven LDC strains gave 0.3-18% hybridisation with that of M. leprae, 5-16% with reference corynebacteria, 5-12% with M. bovis, and 2-8% with Nocardia caviae. The small size of the LDC genome and its unrelatedness to those of M. leprae and organisms of the CMN group shows the uniqueness of LDC.

Molecular-genetic evidence for the relationship of Mycobacterium leprae to slow-growing pathogenic mycobacteria.

A total of 1170 nucleotides of the 16S rRNA from Mycobacterium leprae were compared to the homologous regions of M. tuberculosis, M. bovis Vallée, M. avium, M. scrofulaceum, M. phlei, M. fortuitum and one representative each of the genera Corynebacterium, Nocardia, and Rhodococcus. Homology values were calculated and a phylogenetic tree was constructed from the evolutionary distance values. Despite differences in DNA G + C content and genome size, M. leprae is a true member of the slow-growing pathogenic mycobacteria, branching off intermediate to the other members of this subgroup. Slow- and fast-growing mycobacteria are phylogenetically well separated but constitute an individual branch of the actinomycetes proper. Significant structural variation of certain regions of the 16S rRNA may allow construction of M. leprae-specific probes used for rapid identification.

Properties of microorganisms isolated from human leprosy lesions.

Diphtheroids, which in addition to Mycobacterium leprae are present in human leprosy lesions, were identified as true corynebacteria by DNA and cell wall analysis. Peptidoglycan (adjuvant) of these leprosy-derived corynebacteria (LDC) consists of N-acetylglycosaminyl-N-acetyl(glycolyl)-muramic acid and L-Ala-D-Glu(NH2)-(L)-meso-A2pm-(L)-D-Ala (A2pm = diaminopimelic acid). (The amino group of the tetrapeptide is attached to the carboxyl group of the muramate). Peripheral polysaccharide (antigen) is arabinogalactomannan with lateral chains of mannofuranose and arabinofuranose. To the latter are linked mycolic acids containing groups of isomers with 24-36 carbon atoms and containing between zero and four double bonds. DNAs of LDC isolates have a guanine + cytosine content of 56% and demonstrate a high degree of homology. LDC ribosomes cross-react with antisera against mycobacteria and with sera from patients with leprosy. Thermostable antigen M of LDC cross-reacts with the main antigens of tuberculin and lepromin. LDC thus represents a homogeneous and unique group of corynebacteria immunologically related to M. leprae. Leprosy might be the result of a pathogenic cooperation between both organisms, as suggested by the enhancement of M. leprae growth rate promoted in mice by living LDC.

DNA isolated from Mycobacterium leprae: genome size, base ratio, and homology with other related bacteria as determined by optical DNA-DNA reassociation.

DNA derived from Mycobacterium leprae (grown in armadillos) was isolated, purified, and analyzed spectrophotometrically. The genome size and guanine-plus-cytosine content of M. leprae were 1.3 X 10(9) and 55.8%, respectively. Among selected strains of mycobacterial, nocardial and corynebacterial species, Corynebacterium sp. 2628 LB, isolated from a human leprosy patient, showed the highest DNA homology with M. leprae. Of the DNAs derived from mycobacteria, those of M. tuberculosis and M. scrofulaceum showed a comparatively high reassociation with the DNA of M. leprae.

DNA isolated from Mycobacterium leprae: genome size, base ratio, and homology with other related bacteria as determined by optical DNA-DNA reassociation.

DNA derived from Mycobacterium leprae (grown in armadillos) was isolated, purified, and analyzed spectrophotometrically. The genome size and the guanine-plus-cytosine content of M. leprae were 1.3 x 10(9) and 55.8%, respectively. Among selected strains of mycobacterial, nocardial, and corynebacterial species, Corynebacterium sp. 2628 LB, isolated from a human leprosy patient, showed the highest DNA homology with M. leprae. Of the DNAs derived from mycobacteria, those of M. tuberculosis and M. scrofulaceum showed a comparatively high reassociation with the DNMA of M. liprae.