Evidence that Accumulation of Mutants in a Biofilm Reflects Natural Selection Rather than Stress-Induced Adaptive Mutation

• Published in: Applied and Environmental Microbiology Vol. 73; no. 1; pp. 357 - 361
• Main Authors: Banas, Jeffrey A, Miller, Justin D, Fuschino, Meghan E, Hazlett, Karsten R.O, Toyofuku, Wendy, Porter, Kristen A, Reutzel, Sarah B, Florczyk, Matthew A, McDonough, Kathleen A, Michalek, Suzanne M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.01.2007
• Subjects: Adaptation, Physiological; Animals; Bacterial Proteins - genetics; Biofilms; Biofilms - growth & development; Biological and medical sciences; Carrier Proteins - genetics; Dental Plaque - microbiology; Fundamental and applied biological sciences. Psychology; Gene Deletion; Genotype & phenotype; Glucosyltransferases - genetics; Heat-Shock Response; Humans; Lectins - genetics; Microbial Ecology; Microbiology; Mutation; Pathogens; Rats; Selection, Genetic; Streptococcus mutans; Streptococcus mutans - genetics; Streptococcus mutans - growth & development; Streptococcus mutans - pathogenicity; Biofilm; Mutation; Selection; Accumulation; Stress
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.02014-06

The accumulation of mutant genotypes within a biofilm evokes the controversy over whether the biofilm environment induces adaptive mutation or whether the accumulation can be explained by natural selection. A comparison of the virulence of two strains of the dental pathogen Streptococcus mutans showed that rats infected with one of the strains accumulated a high proportion (average, 22%) of organisms that had undergone a deletion between two contiguous and highly homologous genes. To determine if the accumulation of deletion mutants was due to selection or to an increased mutation rate, accumulations of deletion mutants within in vitro planktonic and biofilm cultures and within rats inoculated with various proportions of deletion organisms were quantified. We report here that natural selection was the primary force behind the accumulation of the deletion mutants.