Hit the right spots: cell cycle control by phosphorylated guanosines in alphaproteobacteria

Recent studies have provided insights into the antagonistic roles of cyclic-di-GMP (c-di-GMP) and the alarmones guanosine tetraphosphate and guanosine pentaphosphate (collectively referred to as (p)ppGpp) in the regulation of the cell cycle in Alphaproteobacteria. In this Review, Viollier and colleagues discuss how those second messengers control the initiation of DNA replication and cytokinesis by modulating the synthesis and proteolysis of key regulators of the cell cycle.