The flexibility of UV-inducible mutation in Deinococcus ficus as evidenced by the existence of the imuB–dnaE2 gene cassette and generation of superior feather degrading bacteria

The lexA–imuB–dnaE2 gene cassette contributing to the TLS (translesion synthesis) polymerase activity and can easily cause mutation after DNA damage in many bacteria. But it was previously thought that TLS polymerase activity was unlikely to exist in the radio-resistant genus Deinococcus. In our preliminary studies, the lexA–imuB–dnaE2 gene cassette was found in a newly isolated feather-degrading Deinococcus ficus. Here we have attempted to determine the imuB gene sequence from another Deinococcus species namely D. grandis, by using the newly designed primers. The destroying of either imuB or dnaE2 gene in D. ficus leads to the increase in UV sensitivity and decrease in UV-induced mutations, which demonstrated the existence of TLS polymerase activity in D. ficus. In the presence of lexA–imuB–dnaE2, it is possible to obtain mutants with various keratinolytic activities after UV exposure. The keratinolytic activity of mutant strain CC-ZG207 increased by approximately twofold during growth in liquid feather medium. In contrast, the mutant strain CC-ZG227 showed only half of the keratinolytic activity compared with the wild type strain. By utilizing SDS–PAGE and zymogram profile analysis, the change in the protease activity was observed. We have proposed that the superior mutants of D. ficus can be created under UV stress, which is mediated by the lexA–imuB–dnaE2 gene cassette.