Haloalkane dehalogenases are microbial enzymes that catalyze cleavage of the carbon-halogen bond by a hydrolytic mechanism. Until recently, these enzymes have been isolated only from bacteria living in contaminated environments. In this report we describe cloning of the dehalogenase gene dhmA from Mycobacterium avium subsp. avium N85 isolated from swine mesenteric lymph nodes. The dhmA gene has a G؉C content of 68.21% and codes for a polypeptide that is 301 amino acids long and has a calculated molecular mass of 34.7 kDa. The molecular masses of DhmA determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by gel permeation chromatography are 34.0 and 35.4 kDa, respectively. Many residues essential for the dehalogenation reaction are conserved in DhmA; the putative catalytic triad consists of Asp123, His279, and Asp250, and the putative oxyanion hole consists of Glu55 and Trp124. Trp124 should be involved in substrate binding and product (halide) stabilization, while the second halide-stabilizing residue cannot be identified from a comparison of the DhmA sequence with the sequences of three dehalogenases with known tertiary structures. The haloalkane dehalogenase DhmA shows broad substrate specificity and good activity with the priority pollutant 1,2-dichloroethane. DhmA is significantly less stable than other currently known haloalkane dehalogenases. This study confirms that a hydrolytic dehalogenase is present in the facultative pathogen M. avium. The presence of dehalogenase-like genes in the genomes of other mycobacteria, including the obligate pathogens Mycobacterium tuberculosis and Mycobacterium bovis, as well as in other bacterial species, including Mesorhizobium loti, Xylella fastidiosa, Photobacterium profundum, and Caulobacter crescentus, led us to speculate that haloalkane dehalogenases have some other function besides catalysis of hydrolytic dehalogenation of halogenated substances.Haloalkane dehalogenases catalyze hydrolytic cleavage of carbon-halogen bonds in halogenated aliphatic compounds, leading to the formation of primary alcohols, halide ions, and protons. These enzymes are potentially useful for cleaning up contaminated subsurfaces (32) and for processing by-products of chemical syntheses (33). Haloalkane dehalogenases can serve as a model system for studies of the evolution and distribution of degradation enzymes in the environment since many of these enzymes have already been isolated from different bacterial species originating from geographically distinct areas (26). Haloalkane dehalogenases have primarily been isolated from bacteria colonizing environments contaminated by halogenated substances (12,16,22,(27)(28)(29)(30)40). Only recently have the hydrolytic dehalogenation activities of several species of the genus Mycobacterium isolated from clinical material been reported (14). Motivation for the search for haloalkane dehalogenases in clinical samples of mycobacteria came from the identification of dehalogenase-like genes in the genome of Mycobacterium tuberculosis...

This study compares the genetic variation in seven cattle breeds from theterritory ofCentralEurope. Eleven polymorphic microsatellite loci were used to detect differences in the polymorphism of genetic markers in Czech Pied (Simmental), Slovakian Pied (Simmental), Slovakian Pinzgau,Holstein, Polish Red, German Red, and Czech Red breeds. For these loci, allele frequencies, heterozygosity, polymorphism information content, effective population size, and genetic distances were evaluated. The phylogenetic tree was constructed using the unweighted pair group method with arithmetic mean and it showed that the Central European Red breeds tended to cluster together, whereas theHolstein was the most divergent from the remaining breeds. These data are discussed in the context of the known origin of respective breeds.  

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ABSTRACT:The Old Kladruber horse is the oldest original Czech horse breed -gene resource, with pedigree records spanning three centuries. Because the population is closed, there is a concern about the loss of genetic variation. The genetic diversity within and amongst sire lines was evaluated using microsatellite markers and based on pedigree information. The DNA analysis, covering 16 microsatellite loci, revealed that the genetic diversity (observed heterozygosity = 0.637, genetic diversity = 0.678 and the mean number of alleles = 8.25) for the Old Kladruber horse is consistent with other populations of horses. Inter-line genetic difference in sire lines reached the mean value (the F ST values ranged from 0.020 to 0.017). Differences amongst the sire lines were identified using genetic distances and principal component analysis. One gene cluster comprised black variation sire lines, while the second cluster included the sire lines of the grey variation. In the subjects monitored, the average inbreeding coefficient of 0.076 was estimated on the basis of pedigree information. The highest mean values of the coefficient of relationship were estimated within the colour variations. When comparing the genetic distance and the average coefficient of relationship, differences were found out. These results are useful for the development of breeding strategies which consider classical horse breeding as well as recent achievements of population and conservation genetics.