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 abnormal proteins, targeting these proteins for proteolytic degradation. Although the conservation of tmRNA throughout the bacterial kingdom suggests that it must provide a strong selective advantage, it has not been shown to be essential for any bacterium. We report that tmRNA is essential in Neisseria gonorrhoeae. Although tagging per se appears to be required for gonococcal viability, tagging for proteolysis does not. This suggests that the essential roles of tmRNA in N.gonorrhoeae may include resolving stalled translation complexes and/or preventing depletion of free ribosomes. Although derivatives of N.gonorrhoeae expressing Escherichia coli tmRNA as their sole tmRNA were isolated, they appear to form colonies only after acquiring an extragenic suppressor(s).