Comparison of RNA-seq of Actinobacillus pleuropneumoniae (WT and (p)ppGpp0) under the absence of branched chain amino acids

(p)ppGpp is a key player in reprogramming transcriptomes to respond to nutritional challenges. Here, we present a transcriptional and phenotypic differences of A. pleuropneumoniae grown in different chemically defined media in the absence of (p)ppGpp. We show that the deprivation of branch-chain amino acids (BCAAs) does not elicit a change in the basal level (p)ppGpp, but this level is sufficient to regulate the expression of BCAA biosynthesis. The mechanism found in A. pleuropneumoniae is different to that of the model organism Escherichia coli, but similar to that found in some Gram-positive bacteria. This study not only broadens the research scope of (p)ppGpp, but also further validates the complexity and multiplicity of (p)ppGpp regulation in microorganisms that occupy different biological niches.