Charged tmRNA but not tmRNA-mediated proteolysis is essential for Neisseria gonorrhoeae viability

tmRNA, through its tRNA and mRNA properties, adds short peptide tags to abn ormal proteins, targeting these proteins for proteolytic degradation. Altho ugh the conservation of tmRNA throughout the bacterial kingdom suggests tha t it must provide a strong selective advantage, if has not been shown to be essential for any bacterium. We report that tmRNA is essential in Neisseri a gonorrhoeae. Although tagging per se appears to be required for gonococca l viability, tagging for proteolysis does not. This suggests that the essen tial roles of tmRNA in N. gonorrhoeae may include resolving stalled transla tion complexes and/or preventing depletion of free ribosomes. Although deri vatives of N. gonorrhoeae expressing Escherichia coli tmRNA as their sole t mRNA were isolated, they appear to form colonies only after acquiring an ex tragenic suppressor(s).