| Abstract | Anthrax is a deadly disease caused by the gram-positive bacterium Bacillus anthracis. In order to be fully virulent, the bacteria must exhibit lethal factor toxin, edema toxin, protective antigen, and a capsule. We have previously shown that another virulence factor is clpXP, an intracellular protease that degrades specific proteins. The loss of clpX in B. anthracis led to a decrease in pathogenesis and increase in antibiotic and antimicrobial peptide susceptibility. It has been shown in Streptococcus pneumoniae that a more positively charged cell wall has lead to increased antimicrobial peptide resistance. Due to the natural positive charge of antimicrobial peptides of the innate immune system, they are thought to be repelled by a positively charged cell wall. We hypothesize that the loss of clpX induces a net negative charge, which makes the mutant bacteria more susceptible to AMPs and thus contributes to the decrease in virulence. We also investigated the regulation of the dlt operon which is known to control cell charge in other bacteria species. We used Cytochrome C, a positively charged red dye, and Poly-L-lysine, a positively charged fluorescent dye, to compare the cell charge of the clpX mutant and its parent strain. |
