ACSS2 and infection: Although CrbS/R regulates expression of acs in both Pseudomonas and Vibrio, this signaling system does not play a similar role in the pathogenesis of the two organisms towards Drosophila. V. cholerae regulation of short chain fatty acid levels in the fly alimentary canal is critical to its success as a pathogen in an oral model of infection [7], but an acs mutant of P. entomophila was not similarly defective in virulence (Fig 9).