How clonal are bacteria?

Abstract

Data from multilocus enzyme electrophoresis of bacterial populations were analyzed using a statistical test designed to detect associations between genes at different loci. Some species (e.g., SalmoneUa) were found to be clonal at all levels of analysis. At the other extreme, Neisseria gonorrhoeae is panmictic, with random association between loci. Two intermediate types of population structure were also found.Neisseria meningitidis displays what we have called an "epidemic" structure. There is significant association between loci, but this arises only because of the recent, explosive, increase in particular electrophoretic types; when this effect is eliminated the population is found to be effectively panmictic. In contrast, linkage disequilibrium in a population of Rhizobium meliloti exists because the sample consisted of two genetically isolated divisions, often fixed for different alleles: within each division association between loci was almost random. The method of analysis is appropriate whenever there is doubt about the extent of genetic recombination between members of a population. To illustrate this we analyzed data on protozoan parasites and again found panmictic, epidemic, and clonal population structures.

Genetic characterization ofMycobacterium aviumisolates recovered from humans and animals in Australia

“…This index, which describes multilocus linkage disequilibrium in bacterial populations [39], is significantly different from zero for a clonal population.…”

Emerging issues and parasite zoonoses in the SE Asian and Australasian region

“…The population genetic structure for protozoan parasites with both sexual and asexual 91 modes of reproduction, such as T. gondii, is usually categorised as one of the following: 92 clonal, where recombination is so infrequent that it does not disrupt genealogical 93 relationships; panmictic, where recombination occurs regularly enough to create fully 94 reticulate relationships; or epidemic, where an underlying panmictic structure is obscured 95 by clonal expansion of a few genotypes (Smith et al, 1993). In Europe and North 96 America, T. gondii has a remarkably clonal population structure, with just three 97 predominant clonal lineages, referred to as Types I, II and III, accounting for >95% of 98 strains isolated from humans and domestic animals (Howe and Sibley 1995).…”

Host adapted serotypes of Salmonella enterica

“…This can be attributed to horizontal genetic transfer and recombination of antigen genes between lineages, an event that has been proposed to happen with relatively high frequency [22]. However, overall the subspecies remain clonal [23].…”