|Meinersmann, Richard - Rick|
Submitted to: International Journal of Systematic and Evolutionary Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/12/1999
Publication Date: 12/20/2002
Citation: MEINERSMANN, R.J., PATTON, C.M., EVIN, G.M., WACHSMUTH, I.K., FIELDS, P.I. GENETIC DIVERSITY AND RELATIONSHIPS OF CAMPYLOBACTER SPECIES AND SUBSPECIES. INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY. 2002. Interpretive Summary: Campylobacter is probably the most common cause of infectious diarrhea disease in humans. Poultry products are the most common source of human infection. Strains of Campylobacter are highly variable and it is difficult to relate characteristics of the strains to the type of disease they cause. Population genetics is a way of analyzing multiple genetic components to determine associations of genes with specific traits. The study involves characterizing the products of several variable genes to determine which variant is present for each gene. Statistical analyses are then performed to determine the relationships of variants of all the genes to see if some occur together more often than expected. This study showed that Campylobacter readily shares genes between different strains, indicating that the exchange of DNA must take place. However, there were some genes that appear to be much less involved in exchange. These genes are more accurate in reflecting the evolutionary history of strains. Evidence was suggestive of the existence of division of the species of Campylobacter jejuni into types of strains that regularly reside in chickens and another type that is never found in chickens. Future refinement of these findings may help to focus attention on genes that are specifically needed for growth of the bacteria in chickens.
Technical Abstract: The genetic diversity within the Campylobacter genus was assessed by multilocus enzyme electrophoresis of 156 isolates of 11 species and subspecies from disparate sources. Analyses of electropheretic mobility of 11 enzymes revealed 109 electrophoretic types (ETs) and 118 ETs when nulls were counted as an allele. Cluster analysis placed most ETs into groups that correlated with species. With nulls counted as alleles, 19 ETs were identified among 33 isolates of C. lari, 31 ETs among 34 isolates of C. coli, and 43 ETs among 59 isolates of C. jejuni subsp. jejuni. Ten C. jejuni subsp. jejuni isolates, species confirmed by DNA/DNA hybridization, were hippuricase negative. Reported linkage analyses were done with nulls ignored. Average genetic diversity (H) scores were high for the total population (average H = 0.802). Allelic mismatch-frequency distributions and allelic tracing pointed to possible genetic exchange between sub-populations. C. lari appears to be a panmictic species. Some pairs of species shared multiple alleles of certain loci, possibly indicating genetic exchange between species. C. jejuni appeared to be the most active in sharing alleles of the species tested. However, there was evidence of variable involvement in recombination by the different loci and linkage analysis of loci in C. jejuni and C. coli revealed a clonal framework with some loci tightly linked to each other. The loci appeared to occur in linkage groups or islands. Campylobacter may have a clonal framework with other portions of the genome involved in frequent recombination.