One cannot rule them all: Are bacterial toxins-antitoxins druggable?

Chan, Wai Ting; Balsa, Dolors; Espinosa, Manuel

Some toxins are bactericidal, as it should be for an 'ideal' antibacterial, so that the infecting bacteria would be killed by the toxin (Zielenkiewicz and Ceglowski 2005; Mutschler and Meinhart 2011) . However, stasis and dormancy due to temporal reduction of the cell growth is a more common effect of the toxin, and this bacteriostatic effect can be reversed by induction of the antitoxin (Pedersen, Christensen and Gerdes 2002; Maisonneuve et al., 2011; Germain et al., 2013) . Recovery of the dormancy due to the toxin may be only effective during a given time period, and prolonged exposure of the bacteria to a toxin like RelE can lead to cell lethality (Nieto et al., 2006) . In addition, there are also some other factors to be considered if toxin alone is the one to be administered, since there are instances in which the toxin may have a different panorama of toxicity in different hosts, e.g. expression of toxin Zeta of plasmid pSM19035, which was discovered in S. pyogenes, is bactericidal for the Grampositive Bacillus subtilis and bacteriostatic for the Gram-negative E. coli (Zielenkiewicz and Ceglowski 2005) .