Bacillus globigii cell size is influenced by variants of the quorum sensing peptide extracellular death factor

Abstract

Toxin-antitoxin modules are necessary for the mode of action of several antibiotics. One of the most studied toxin-antitoxin modules is the quorum sensing-dependent MazEF system in Escherichia coli. The quorum sensing factor in this system is called the extracellular death factor (EDF), a linear pentapeptide with the sequence NNWNN. In spite of the extensive research on the mazEF system and the involvement of the quorum sensing factor EDF, the effect of EDF itself on bacteria has not yet been studied. In this research, we determined the effect of EDF and variants on cell growth in the Gram-negative bacterium E. coli and the Gram-positive Bacillus globigii. By aligning the zwf gene (from where EDF originates) of different bacterial species, we found 27 new theoretical variants of the peptide. By evaluating growth curves and light microscopy we found that three EDF variants reduced bacterial cell size in B. globigii, but not in E. coli. The D-peptides did not affect cell size, indicating that the effect is stereospecific. Peptides wherein tryptophan was substituted by alanine also did not affect cell size, which indicates that the effect seen is mediated by an intracellular target.

Structural basis ofBacillus anthracisMoxXT disruption and the modulation of MoxT ribonuclease activity by rationally designed peptides

“…A number of EDFs have been identified in B. subtilis and P. aeruginosa that can also trigger MazF activity, but their binding site is not known (Kumar et al, 2013). Independently, a number of EDF precursor peptides derived from zwf gene that codes for glucose 6-phosphate dehydrogenase (G6PDH) in different organisms have been shown to cause decrease in cell size in B. globigii (Sijbrandij et al, 2013). Peptides designed by similarity to MoxX and MazE were previously shown to be successful in disruption of MoxXT complex (Agarwal et al, 2010), a type II TA system characterized in B. anthracis (Agarwal et al, 2007).…”