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

Enhancing the antimicrobial activity of Sus scrofa lysozyme by N-terminal fusion of a sextuple unique homologous peptide

Sus scrofa lysozyme (SSL), an important component of the pig immune system, is a potential candidate to replace antibiotics in feed. However, there is little antimicrobial activity of natural SSL against gram-negative bacteria, which limits its application. In this study, a unique peptide (A-W-V-A-W-K) with antimicrobial activity against gram-negative bacteria was discovered and purified from trypsin hydrolysate of natural SSL. This unique peptide was fused to natural SSL and the recombinant fused SSL exhibited improved activity against gram-negative bacteria. The N-terminal fusion likely increased the membrane penetrability and induced programmed bacterial cell death. The recombinant fused SSL also showed higher activity against some gram-positive bacteria with O-acetylation. By N-terminal fusion of the sextuple peptide, the anti-microbial activity, either to gram-positive or negative bacteria, of the recombinant SSL was higher than the fusion of only one copy of the peptide. This study provides a general, feasible, and highly useful strategy to enhance the antimicrobial activity of lysozyme.

Structural basis of Bacillus anthracis MoxXT disruption and the modulation of MoxT ribonuclease activity by rationally designed peptides

Bacillus anthracis MoxXT is a Type II proteic Toxin-Antitoxin (TA) module wherein MoxT is a ribonuclease that cleaves RNA specifically while MoxX interacts with MoxT and inhibits its activity. Disruption of the TA interaction has been proposed as a novel antibacterial strategy. Peptides, either based on antitoxin sequence or rationally designed, have previously been reported to disrupt the MoxXT interaction but cause a decrease in MoxT ribonuclease activity. In the present study, we report the crystal structure of MoxT, and the effect of several peptides in disrupting the MoxXT interaction as well as augmentation of MoxT ribonuclease activity by binding to MoxT in vitro. Docking studies on the peptides were carried out in order to explain the observed structure activity relationships. The peptides with ribonuclease augmentation activity possess a distinct structure and are proposed to bind to a distinct site on MoxT. The docking of the active peptides with MoxT showed that they possess an aromatic group that occupies a conserved hydrophobic pocket. Additionally, the peptides inducing high ribonuclease activity were anchored by a negatively charged group near a cluster of positively charged residues present near the pocket. Our study provides a structural basis and rationale for the observed properties of the peptides and may aid the development of small molecules to disrupt the TA interaction.