Presence of the two-component regulatory system ComD, and its transcription in the ruminal bacterium Streptococcus bovis
2010
Yoshii, T., Meiji Univ., Kawasaki, Kanagawa (Japan). School of Agriculture | Asanuma, N. | Yoshizawa, K. | Arai, Y. | Kanada, Kino | Hino, T.
To elucidate the regulatory mechanisms of Streptococcus bovis growth, we investigated the molecular properties and gene expression of the peptide pheromone-signaling system, which is encoded by three genes, comC, comD, and comE, via the competence-stimulating peptide ComC. In S. bovis, these genes were found to be clustered, but comC was present on the DNA strand opposite to the strand harboring comD and comE. Genes that are homologous to comD and comE were also present in the neighborhood of the comCDE cluster. The ComC contained the Gly-Gly cleavage site, which is a specific position to cut off the leader peptide. The motif sequences for histidine kinase were conserved in ComD and its homologs. The LytTR family DNA-binding domain was found in ComE and its homolog. These results suggest that these Com proteins function in a two-component system. It was demonstrated by RT-PCR and real-time RT-PCR that comE and comD are cotranscribed and comC is transcribed in a monocistronic fashion. The comC-mRNA level increased sharply during initial exponential growth, and decreased during the late exponential phase, which was similar to other com gene-mRNAs. Thus, the transcription of com genes in S. bovis appears to change with the growth phase.
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