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The carbon catabolite repressor CcpA mediates optimal competence development in Streptococcus oligofermentans through post‐transcriptional regulation
Author(s) -
Wang Xinhui,
Cai Jun,
Shang Nan,
Zhu Lin,
Shao Nana,
Dong Xiuzhu,
Tong Huichun
Publication year - 2019
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14274
Subject(s) - ccpa , biology , repressor , operon , catabolite repression , terminator (solar) , transcription (linguistics) , general transcription factor , promoter , lac operon , transfer rna , antitermination , mutant , microbiology and biotechnology , rna , gene , transcription factor , genetics , plasmid , gene expression , ionosphere , linguistics , philosophy , physics , astronomy
Summary Natural transformation increases the genetic diversity of bacteria, but is costly and must be strictly controlled. We previously found that deletion of ccpA , a key regulator of carbon catabolite repression (CCR), reduced transformation efficiency of Streptococcus oligofermentans , the current work further investigated the regulatory mechanisms of CcpA. The competence operon comCDE is subjected to basal and autoregulatory transcription. A luciferase reporter detected a transcriptional readthrough (TRT) from the upstream tRNA Arg into the comCDE operon, which was induced by L ‐arginine. Insertion of the Escherichia coli T1T2 terminator downstream of tRNA Arg abolished TRT, and reduced the basal comCDE transcription by 77% and also the transformation efficiency. Deletion of ccpA increased tRNA Arg TRT and tRNA Arg ‐ comCDE polycistronic transcript by twofold. An in vitro transcription assay determined that CcpA promoted the transcription termination of tRNA Arg TRT, and RNA EMSA and SPR assays detected equal binding affinity of CcpA to both the RNA and DNA of tRNA Arg . These results indicate that CcpA controls the basal comCDE transcription by post‐transcriptional actions. Overexpression of comDE or its phospho‐mimicking mutant comDE D58E reduced transformation efficiency, indicating that excessive ComE impairs competence development. CCR‐regulated competence was further confirmed by higher tRNA Arg TRT but lower transformation efficiency in galactose than in glucose.