Gene controlling aggregate size:
Aggregate size control utilizes secreted counting factor complex comprising proteins countin, cf45, cf50, cf60, and regulatory small proteins SmlA and SslA. SmlA encodes small hydrophobic protein that negatively regulates counting factor secretion. As aggregate gathers more cells, counting factor concentration rises informing cells about group size through inhibition of adhesion and motility. Loss of counting factor produces excessively large aggregates, while mutations in small regulators like smlA alter complex abundance. Adenylyl cyclase genes govern cAMP signaling rather than quorum sensing. Therefore smlA participates in community size sensing mechanism analogous to bacterial quorum regulation but mediated by secreted proteins.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 22: Counting factor and smlA regulation of aggregate size.