Member of the two-component regulatory system AtoS/AtoC. In the presence of acetoacetate, AtoS/AtoC stimulates the expression of the atoDAEB operon, leading to short chain fatty acid catabolism and activation of the poly-(R)-3-hydroxybutyrate (cPHB) biosynthetic pathway. Also induces the operon in response to spermidine (PubMed:16153782, PubMed:16564134, PubMed:17475408). Involved in the regulation of motility and chemotaxis, via transcriptional induction of the flagellar regulon (PubMed:22083893). AtoS is a membrane-associated kinase that phosphorylates and activates AtoC in response to environmental signals (PubMed:16153782, PubMed:18534200). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Homodimer. Autophosphorylated (PubMed:16153782, PubMed:18534200). Each AtoS molecule may phosphorylate its partner within the dimer rather than phosphorylating itself (PubMed:18534200). Deletion of the atoSC locus renders cells not motile or responsive against any chemoattractant or repellent independently of the atoSC inducer's presence.