Chapter 7 - Pneumococcal Genetic Transformation During Colonization and Biofilm Formation

Abstract

Transformation of genetic material between bacteria was first observed in the 1920s using Streptococcus pneumoniae as a model organism. Since then, our understanding of the mechanisms involved in competence induction, DNA uptake, homologous recombination, and the regulation of these processes have been greatly improved, mainly using in vitro model systems. However, epidemiologic evidence suggests that genetic exchange occurs primarily during pneumococcal nasopharyngeal carriage that occurs in the form of biofilm growth, and is associated with co-colonization with multiple strains. In this chapter we discuss the mechanisms of genetic exchange, especially as it pertains to biofilm formation and nasopharyngeal colonization and its implications for evolution of fitness and adaptation to clinical intervention. Current information suggests that transformation is especially effective when pneumococci grow as biofilms during colonization, which may have important clinical consequences by facilitating the spread of antibiotic resistance, as well as enabling serotype switching and vaccine escape.