Analysis of the Genome of Chromium-resistant Serratia sp. CM01 and Chromium Metabolism Characteristics of the ChrA1-Srpc Gene

Objective: Serratia sp. CM01 is a naturally domesticated strain with chromium (Cr) resistance and Cr(VI) reduction ability isolated from a Cr-enriched environment. The genome of Serratia sp. CM01 was sequenced and analysed to identify key genes involved in chromium metabolism. Corresponding engineered bacteria associated with special metabolic features were constructed to further study the function of these genes and their encoded proteins in chromium metabolism. Methods: : The whole genome of Serratia sp. CM01 was sequenced, and genes involved in chromium metabolism were analysed. The ChrA1 and Srpc genes were selected and introduced into E. coli using the prokaryotic expression vector pET-28a. The target proteins were identified using sodium dodecyl sulphate‒polyacrylamide gel electrophoresis ( SDS‒PAGE ) and Western blotting. Chromium tolerance and removal tests were used to assess the chromium metabolic capabilities of the engineered bacteria. Results: : The results of genome sequencing revealed that the genome size of Serratia sp. was 4,902,254 bp, from which 12 genes involved in chromium metabolism were screened. The ChrA1 and Srpc genes were chosen, and three engineered bacteria (eChrA1, eSrpc, and eCS) were successfully constructed. The growth of the three engineered bacteria showed no difference under Cr(VI)-free circumstances (P > 0.05). In the presence of Cr(VI), the viable bacterial cell mount during the stabilization phase was eCS > eChrA1 > eSrpc, and the tolerance and removal rate of Cr(VI) was ranked eCS > eChrA1 > eSrpc. Conclusion: The genome of Serratia sp. CM01 contains genes related to chromium metabolism, such as NemA, ChrA1, Srpc and FieF . The ChrA1 and Srpc gene-encoded proteins confer Cr(VI) resistance to engineered bacteria, but the specific mechanism of chromium resistance remains to be further studied. eChrA1 has a stronger anti-Cr(VI) ability than eSrpc. The eCS-engineered bacterial strain with ChrA1 and Srpc genes was more resistant to hexavalent chromium, and it has the potential to handle Cr(VI) pollution in the virtual environment.