Purification and characterization of CcdB and CcdA toxin-antitoxin system from Acetobacter malorum.

The toxin-antitoxin (TA) system, a genetic element in microorganisms, consists of a stable toxin and an unstable antitoxin. The CcdAB system, a typical TA system, encodes the CcdB toxin and CcdA antitoxin and was identified in Acetobacter, though its biological role remains unclear. In this study, CcdA and CcdB proteins were successfully expressed, and purification conditions were optimized to obtain high-purity proteins. Their interaction was studied using a pull-down assay and confirmed through bioinformatics tools, revealing stable secondary structures. Induced expression of CcdB inhibited E. coli growth, demonstrating its toxic effect. Additionally, the structures of CcdA and CcdB were predicted, with structural alignment showing CcdB's evolution is highly conserved. These findings enhance understanding of the CcdA-CcdB interaction mechanism, providing a foundation for further research on TA systems in acetic acid bacteria and their potential roles in microbial survival and stress responses.