ACP3 and infection: In P. aeruginosa, the stringent response mediated by SpoT has been shown to be essential for the detection of fatty acid starvation via activation of SpoT by the acyl carrier protein AcpP, for the expression of usp genes encoding universal stress proteins, and for full virulence in eukaryotic infection models (Boes et al., 2008; Battesti and Bouveret, 2009; Vogt et al., 2011).