Multilocus Enzyme Electrophoresis Methods for the Analysis of Bacterial Population Genetic Structure

Abstract

The field of population biology can be divided into two disciplines: population genetics and population ecology (Hedrick, 1984). Studies in population genetics address questions on the genetic composition of populations, whereas studies in population ecology focus on environmental and biological factors influencing the numbers of organisms in populations. Several texts have been written on the ecology of soil bacteria (e.g., Atlas & Bartha, 1987; Campbell, 1984), whereas the existing literature on the genetic structure of bacterial populations in soils is limited to several studies (Demezas et aI., 1991; Denny et aI., 1988; Eardly et aI., 1990; Engvild et aI., 1990; McArthur et aI., 1988; Pinero et aI., 1988; Segovia et aI., 1991; Young, 1985). Genetic structure is a useful, although somewhat ambiguous term, that is used to describe both the phylogenetic relatedness and the genetic diversity that exists in natural populations of organisms. Most studies examining the genetic structure of natural populations are intended to reveal basic information on the evolutionary development of a particular group or species. Oftentimes this involves studies of many subpopulations that may be taken to represent an entire taxon. Methods that are used to study the genetic structure in populations, such as multilocus enzyme electrophoresis (or MLEE) , should not be confused with other methods where the primary aim is to categorize strains on the basis of a particular characteristic that may be of immediate practical significance (e.g., antibiotic resistance to track a gene in a population). An understanding of the genetic structure of a bacterial population is important for several reasons; it can provide insight into genetic relationships that exist among members of a population, and it can provide a sound framework for designing further ecological, physiological, and genetic studies of that population.