CLPP and infection: ClpP positively regulates biofilm formation, especially primary attachment and PIA production (Figure 3), impacting virulence in a rat IV-catheter infection model.216 Mutations in spx, encoding an RNA polymerase binding protein conserved in the Bacillota, reversed growth and competence defects caused by ClpX or ClpP mutations in Bacillus.222 Deletion of ClpP appears to have no direct effect on ica operon transcription.