Microcins reveal natural mechanisms of bacterial manipulation to inform therapeutic development.

Microcins are an understudied and poorly characterized class of antimicrobial peptides. Despite the existence of only 15 examples, all identified from the , microcins display diversity in sequence, structure, target cell uptake, cytotoxic mechanism of action and target specificity. Collectively, these features describe some of the unique means nature has contrived for molecules to cross the 'impermeable' barrier of the Gram-negative bacterial outer membrane and inflict cytotoxic effects.

Conserved bacterial RNase YbeY plays key roles in 70S ribosome quality control and 16S rRNA maturation.

Quality control of ribosomes is critical for cellular function since protein mistranslation leads to severe physiological consequences. We report evidence of a previously unrecognized ribosome quality control system in bacteria that operates at the level of 70S to remove defective ribosomes. YbeY, a previously unidentified endoribonuclease, and the exonuclease RNase R act together by a process mediated specifically by the 30S ribosomal subunit, to degrade defective 70S ribosomes but not properly matured 70S ribosomes or individual subunits.