Using Genetic Approaches To Delineate the Pathway of Contact-Dependent Growth Inhibition

Abstract

The study of the phenomenon of contact-dependent growth inhibition (CDI) began with the observation that in mixed cultures of Escherichia coli, an E. coli strain from the intestine of a rat designated EC93 inhibited the growth of differentially marked (antibiotic resistances) K-12 bacteria in the same culture. The authors say that they are not aware of the function(s) of contact-dependent growth inhibition (CDI) systems in the many different bacterial genera containing CDI homologues at the time of the writing this chapter, although progress in this area is being made. The chapter is an account of the genetic approaches the authors have used to explore CDI, including some anomalies and stumbling blocks that may be of interest to the reader. To identify the cellular factors that play roles in CDI, the authors took a series of genetic approaches. Initially, a transposon EZ-Tn5 library was constructed in E. coli EPI100 ( Epicentre) target cells. To identify the cellular factors that play roles in CDI, the authors took a series of genetic approaches. They observed a number of mucoid colonies in selection scheme described from which acrB insertions conferring CDI resistance were identified, as well as a similar mutant selection using chemical mutagenesis. To study the mechanism of contact-dependent growth inhibition, the authors developed a CDI autoinhibition system in which growth inhibition is regulated by controlling expression of the cdiI immunity gene. The necessity of an energy source for growth recovery raised the question of what role metabolism plays in CDI.