Intraclonal Polymorphism in Bacteria

Abstract

Before the invention of pure culture methods, bacteria were believed to be fantastically variable-indeed, all the different types observed were thought by some biologists (the pleomorphists) to represent different stages in the life cycles of a few kinds of microbe. Koch's demonstration that each type of bacterium breeds true when grown in pure culture caused the pendulum to swing the other way; it became the majority opinion that bacteria were monomorphic. At the beginning of the twentieth century, however, it became recognized that even the most impeccably pure cultures were able to change, and many bacteriologists began to study the mechanism of such variations.Stanier, Dourdoroff, and Adelberg (1958)

Dental Caries: A Microbiological Approach

“…that are common among strains of a species can be regarded as support of bacteria to survive stresses common to their habitats due to 'stress proteins' [58][59][60][61].…”

Modification of the aggregation behaviour of the environmental Ralstonia eutropha‐like strain AE815 is reflected by both surface hydrophobicity and amplified fragment length polymorphism (AFLP) patterns

“…The fact that, for each of the three primer sets used, the AFLP patterns of the two autoaggregative strains showed similar changes in relation to the control strains seems to indicate that these events do not occur randomly, but that a non-random mechanism is at work at one or more loci. The relation between chromosomal mutational events, other than point mutations, and changes in cell surface composition has been studied in some detail in pathogenic bacteria (Rainey et al, 1993;Moxon et al, 1994), but is poorly documented in environmental strains. In a Pseudomonas atlantica strain, EPS production was found to be modulated by an insertion or deletion of an IS element (Bartlett et al, 1988).…”

Molecular Biology and Pathogenicity of Mycoplasmas

“…The discovery that the minute mycoplasmas possess an impressive capability of maintaining a surface architecture that is antigenically and functionally versatile has placed the mycoplasmas in the "elite" group of bacterial pathogens and parasites distinguished by remarkable antigenic variability (350,381).…”

“…In other words, the major survival strategy of the mycoplasmas seems to depend on random and stochastic processes, consisting of various mutational mechanisms which generate high-frequency phenotypic switching (105,350,381,477,478). Genetic mechanisms of antigenic variation emerging from the mycoplasma studies can be broadly divided into the following three categories (Table 4).…”

“…The essence of this type of variation is the presence of small regions containing reiterated bases (homopolymeric repeats) or oligonucleotide repeats. These "hot spots" provide favorite targets for frequent insertion or deletions of nucleotides and are quite commonly used by several pathogenic bacteria to switch genes ON and OFF (350,381). Loss or gain of nucleotides is thought to occur due to transient misalignment during DNA replication by a process termed slipped-strand mispairing (252).…”