, a Key Gene of the Circadian Rhythm of .

Circadian rhythms are present in almost all living organisms, and their activity relies on molecular clocks. In prokaryotes, a functional molecular clock has been defined only in cyanobacteria. Here, we investigated the presence of circadian rhythms in non-cyanobacterial prokaryotes. The bioinformatic approach was used to identify a homologue of KaiC (circadian gene in cyanobacteria) in . Then, strains of (wild type and mutants) were grown on blood agar, and sampling was made every 3 h for 24 h at constant conditions. Gene expression was determined by qRT-PCR, and the rhythmicity was analyzed using the Cosinor model. We identified RadA as a KaiC homologue in Expression of showed a circadian rhythm persisting at least 3 days, with a peak in the morning. The circadian expression of other genes was also observed. Gene circadian oscillations were lost in mutants of . This study provides evidence of molecular clock gene expression in with a circadian rhythm. Such a finding paves the way for new perspectives in antibacterial treatment.