Genetic structure of Neisseria gonorrhoeae populations: a non-clonal pathogen

Abstract

~~Reproduction by binary fission generates a clonal genetic structure in bacterial populations in the absence of a high rate of recombination. The extent of recombination in natural populations of Neisseria gonorrhoeae was determined from an analysis of electrophoretically demonstrable allelic variation at structural genes encoding nine enzyme loci in 227 worldwide isolates. No significant linkage disequilibrium was evident in the population, indicating that recombination must be frequent, relative to binary fission. The genetic structure of N. gonorrhoeae was compared with that of Bacillus subtilis from an earlier study. Linkage disequilibrium was less extreme in the N. gonorrhoeae population than in the local population of B. subtilis, in which only modest clonal structure was evident. Thus, N. gonorrhoeae, unlike pathogens so far examined, has a non-clonal population structure. As expected in a freely recombining population, no correlation was found between electrophoretic genotype and Serovar or auxotype.

Population genetic analysis of Serpulina pilosicoli and its molecular epidemiology in villages in the Eastern Highlands of Papua New Guinea

“…belonging to the same ET) may be generated by random association of the most common alleles at each locus. In the case of Neisseria gonorrhoea, which has a recombinant population structure, 15 YO of 227 isolates were shown to be located in a single ET, based on the examination of nine enzyme loci (O'Rourke & Stevens, 1993). Subsequent genetic and phenotypical analysis of 26 isolates belonging to this ET showed that they could be divided into 24 distinguishable groups and so were not members of a clone (O'Rourke & Spratt, 1994).…”

“…Among the human isolates, however, only five of the 15 loci examined were polymorphic, with a mean of 2-6 alleles at these loci. In other apparently highly recombinant bacterial species investigated by MLEE, the majority of loci have been polymorphic (O'Rourke & Stevens, 1993;Go et al, 1996;Trott et al, 1997c) and, in the case of H. pylori, there was a mean of 1 1.2 alleles per locus (Go et al, 1996). For this collection of S. pilosicoli isolates, the presence of a majority of monomorphic loci suggests that, if extensive large-scale genetic recombination was occurring, it was for some reason restricted to a minority of loci, or it did not result in detectable alterations in electrophoretic mobility for the other enzymes.…”

Organization of carbamoyl-phosphate synthase genes in Neisseria gonorrhoeae includes a large, variable intergenic sequence which is also present in other Neisseria species

“…These repeats may play a role in the sequence variation observed. Gonococci are noted for their heterogeneity and their ability to be easily transformed with DNA containing the gonococcal uptake sequence (Goodman & Scocca, 1988 ;O'Rourke & Stevens, 1993). The size of the CPS genes themselves is conserved, except for isolates known to be deficient in CPS, for which the evidence suggests that multiple mutations led to the formation of these CPS deficiencies.…”

Sexually transmitted diseases: microbiology and management Proceedings of the Seventh Liverpool Tropical School Bayer Symposium on Microbial Disease held on 6 February 2000

“…N. gonorrhoeae is unique in that it is highly competent for horizontal gene exchange throughout its life cycle. Extensive recombination is thought to occur, particularly during mixed infections in vivo, resulting in a 798 H. BIRLEY, B. I. DUERDEN AND C. A. HART non-clonal or panmictic population [55]. For typing purposes, this genetic diversity can result in a high level of discrimination between strains dependent on the technique or gene chosen.…”