Investigation of the ClpXP protease's connection to Bacillus anthracis cell wall characteristics

Abstract

We recently demonstrated that ClpX is critical for the pathogenesis and resistance to cell wall-acting antimicrobials of Bacillus anthracis, the causative agent of anthrax. ClpXP is an intracellular protease conserved across many bacterial species and is often associated with cellular stresses and has been implicated in the virulence of several pathogens. Antimicrobial resistance to cell wall-acting agents can result from a decrease in autolytic activity and an increase in cell wall charge or thickness. We have examined the genetic expression of autolytic and cell charge-acting genes using real-time quantitative PCR and directly measured these characteristics in a B. anthracis mutant lacking ClpX. We examined structural cell wall differences in our ClpX mutant using scanning and transmission electron microscopy. Our results indicate that the loss of ClpX does not affect the autolytic rate or cell wall charge of B. anthracis, but does result in the thinning of the cell wall.