A total of 246 isolates representing five species of the family Enterobacteriaceae, taken from a variety of Australian mammal species, were characterized using multi-locus enzyme electrophoresis. Genome diversity estimates varied significantly among species, with the Klebsiella pneumoniae sample exhibiting the lowest diversity and the Citrobacterfreundii sample the highest. Multi-locus linkage disequilibrium estimates revealed that alleles were non-randomly associated in all five species samples, but the magnitude of the estimates differed significantly among species. Escherichia coli had the lowest linkage disequilibrium estimate and Klebisella oxytoca the largest. Molecular analyis of variance was used to determine the extent to which population structure explained the observed genetic variation in a species. Two population levels were defined: the taxonomic family of the host from which the isolate was collected and the geographical locality where the host was collected. The amount of explained variation varied from 0% for K. oxytoca to 22% for K. pneumoniae. Host locality explained a significant amount of the genetic variation in the C. freundii (12%), E. coli (5%), Hafnia alvei (17%) and K. pneumoniae (22%) samples. Host family explained a significant fraction of the variation in E. coli (6%) H. alvei (7%) and K. pneumoniae (20%). Estimates of effective population size for all five species, based on the probability that two randomly chosen isolates will be identical, failed to reveal any relationship between the effective population size and the genetic diversity of a species.
Atwood, K. C., Schneider, L. K. & Ryan, F. J. (1951). Periodic selection in Escherichia coli. Genetics37, 146-155.
[Google Scholar]
Bennet, A. F. & Lenski, R. E. (1993). Evolutionary adaptation to temperature. II. Thermal niches of experimental lines of Escherchia coli. Evolution47, 1-12.[CrossRef][Google Scholar]
Bisercic, M., Feutrier, J. Y. & Reeves, P. R. (1991). Nucleotide sequences of the gnd genes from nine natural isolates of Escherichia coli: evidence of intragenic recombination as a contributing factor in the evolution of the polymorphic gnd locus. J Bacteriol173, 3894-3900.
[Google Scholar]
Brown, A. D. H., Feldman, M. W. & Nevo, E. (1980). Multilocus structure of natural populations of Hordeum spontaneum. Genetics96, 523-536.
[Google Scholar]
Caugant, D. A., Levin, B. R. & Selander, R. K. (1981). Genetic diversity and temporal variation in the E. coli populations of a human host. Genetics98, 467-490.
[Google Scholar]
Caugant, D. A., Levin, B. R. & Selander, R. K. (1984). Distribution of multilocus genotypes of Escherichia coli within and between host families. J Hyg92, 377-384.[CrossRef][Google Scholar]
Clemens, W. A., Richardson, B. J. & Baverstock, P. R. (1989). Biogeography and phylogeny of the Metatheria. In Fauna of Australia: Mammalia, vol. 1B, pp. 527-548. Edited by D. W. Walton & B. J. Richardson. Canberra: Australian Government Publishing Service.
Cohan, F. M. (1994). Genetic exchange and evolutionary divergence in prokaryotes. Trends Ecol Evol9, 175-180.[CrossRef][Google Scholar]
Cohan, F. M. (1995). Does recombination constrain neutral divergence among bacterial taxa? Evolution49, 164-175.[CrossRef][Google Scholar]
Drake, J. W. (1991). A constant rate of spontaneous mutation in DNA-based microbes. Proc Natl Acad Sci USA88, 7160-7164.[CrossRef][Google Scholar]
Dubose, R. F., Dykhuizen, D. E. & Hartl, D. L. (1988). Genetic exchange among natural isolates of bacteria: recombination within the phoA gene of Escherichia coli. Proc Natl Acad Sci USA85, 7036-7040.[CrossRef][Google Scholar]
Dykhuizen, D. E. & Green, L. (1986). DNA sequence variation, DNA phylogeny, and recombination in E. coli. Genetics113, S71.
[Google Scholar]
Ewing, W. H. (1986).Edwards and Ewing’s Identification of Enterobacteriaceae, 4th edn. New York: Elsevier.
Excoffier, L., Smouse, P. E. & Quattro, J. M. (1992). Analysis of molecular varience inferred from metric distances among DNA haplotypes: application to human mitochondrial DNA restriction data. Genetics131, 479-491.
[Google Scholar]
Gordon, D. M. (1997). The genetic structure of Escherichia coli populations in feral house mice. Microbiology143, 2039-2046.[CrossRef][Google Scholar]
Gordon, D. M. & FitzGibbon, F. (1999). The distribution of enteric bacteria from Australian mammals: host and geographical effects. Microbiology145, 2663-2671.
[Google Scholar]
Gordon, D. M., Wexler, M., Reardon, T. B. & Murphy, P. J. (1995). The genetic structure of Rhizobium populations. Soil Biol Biochem27, 491-499.[CrossRef][Google Scholar]
Guttman, D. S. (1997). Recombination and clonality in populations of Escherichia coli. Trends Ecol Evol12, 16-22.
[Google Scholar]
Guttman, D. S. & Dykuizen, D. E. (1994). Clonal divergence in Escherichia coli as a result of recombination, not mutation. Science266, 1380-1383.[CrossRef][Google Scholar]
Hartl, D. L. & Dykhuizen, D. E. (1984). The population genetics of Escherichia coli. Annu Rev Genet18, 31-68.[CrossRef][Google Scholar]
Haubold, B. & Rainey, P. B. (1996). Genetic and ecotypic structure of a fluorescent Pseudomonas population. Mol Ecol5, 747-761.[CrossRef][Google Scholar]
Hebert, P. D. N. & Beaton, M. J. (1993).Methodologies for Allozyme Analysis Using Cellulose Acetate Electrophoresis. Beaumont, TX: Helena Laboratories.
Howard, D. J., Bush, G. L. & Breznak, J. A. (1985). The evolutionary significance of bacteria associated with Rhagoletis. Evolution39, 405-417.[CrossRef][Google Scholar]
Lenski, R. E., Mongold, J. A., Sneigowski, P. D., Travisano, M., Vasi, F., Gerrish, P. J. & Schmidt, T. M. (1998). Evolution of competitive fitness in experimental populations of E. coli: what makes one genotype a better competitor than another? Antonie Leeuwenhoek73, 35-47.[CrossRef][Google Scholar]
Levin, B. R. (1981). Periodic selection, infectious gene exchange and the genetic structure of E. coli populations. Genetics99, 1-23.
[Google Scholar]
Maynard Smith, J. (1991). The population genetics of bacteria. Proc R Soc Lond Ser B245, 37-41.[CrossRef][Google Scholar]
Maynard Smith, J., Smith, N. H., O’Rourke, M. & Spratt, B. G. (1993). How clonal are bacteria? Proc Natl Acad Sci USA90, 4384-4388.[CrossRef][Google Scholar]
Milkman, R. (1973). Electrophoretic variation in Escherichia coli from natural sources. Science182, 1024-1026.[CrossRef][Google Scholar]
Milkman, R. & Bridges, M. M. (1993). Molecular evolution of the Escherichia coli chromosome. IV. Sequence comparisons. Genetics133, 455-468.
[Google Scholar]
Nei, M. (1978). Estimation of average heterozygosity and genetic distance from a small number of individuals. Genetics89, 583-590.
[Google Scholar]
Nelson, K. N. & Selander, R. K. (1994). Intergeneric transfer and recombination of the 6-phosphogluconate dehydrogenae gene (gnd) in enteric bacteria. Proc Natl Acad Sci USA91, 10227-10231.[CrossRef][Google Scholar]
Power, D. A. & McCuen, P. L. (1988).Manual of BBL Products and Laboratory Procedures, 6th edn. Cockeysville, MD: Becton Dickinson Microbial Systems.
Pupo, G. M. & Richardson, B. J. (1995). Biochemical genetics of a natural population of Escherichia coli: seasonal changes in alleles and haplotypes. Microbiology141, 1037-1044.[CrossRef][Google Scholar]
Savageau, M. A. (1983).Escherichia coli habitats, cell types, and molecular mechanisms of gene control. Am Nat122, 732-744.[CrossRef][Google Scholar]
Schmidt-Nielsen, K. (1991).Animal Physiology, 5th edn. Cambridge: Cambridge University Press.
Selander, R. K. & Levin, B. R. (1980). Genetic diversity and structure in Escherichia coli. Science210, 545-547.[CrossRef][Google Scholar]
Selander, R. K., Caugant, D. A. & Whittam, T. S. (1987). Genetic structure and variation in natural populations of Escherichia coli. In Escherichia coli and Salmonella typhimurium: Cellular and Molecular Biology, pp. 1625–1648. Edited by F. C. Neidhardt and others. Washington, DC: American Society for Microbiology.
Souza, V., Nguyen, T. T., Hudson, R. R., Piñero, D. & Lenski, R. E. (1993). Hierarchical analysis of linkage disequilibrium in Rhizobium populations: evidence for sex? Proc Natl Acad Sci USA89, 8389-8393.
[Google Scholar]
Strahan, R. (1983).Complete Book of Australian Mammals. Melbourne: Angus & Roberston Publishers.
Wernegreen, J. J., Harding, E. E. & Riley, M. A. (1997).Rhizobium gone native: unexpected plasmid stability of indigenous Rhizobium leguminosarum. Proc Natl Acad Sci94, 5483-5488.[CrossRef][Google Scholar]
Whittam, T. S., Ochman, H. & Selander, R. K. (1983). Geographic components of linkage disequilibrium in natural populations of Escherichia coli. Mol Biol Evol1, 67-83.
[Google Scholar]
Wright, S. (1943). Isolation by distance. Genetics28, 114-138.
[Google Scholar]