UV-induced mutagenesis enhances bacteriocin production in Enterococcus hirae LD3: Genetic and structural characterization

Background

Ultraviolet radiation is generally used to induce mutations in different bacterial genomes to understand structure-function relationship of metabolites. We have previously isolated bacteriocin-producing Enterococcus hirae LD3 from an indigenous fermented food and characterized for probiotic properties. Since bacteriocin production is a genetic phenomenon, we have used UV-radiation to generate mutants for bacteriocin production characterization.

Methods

Mutation was generated using UV radiation at 254 nm and mutants were screened using the level of bacteriocin production. Bacteriocin gene was amplified, sequenced, and phylogenetic and structure analysis was performed using MEGA-11 and I-TASSER software. The molecular docking of wild-type and mutant bacteriocins with target mannose phosphotransferase system (Man-PTS) was performed using BIOVIA discovery studio visualizer to understand the function.

Results

The mutant strain LD3UVM921 showed higher bacteriocin production (320 AU/mL) compared to wild-type strain LD3 (160 AU/mL). The bacteriocin gene showed a deletion of a cytosine residue and guanine to thymine and a cytosine to adenine transversion after UV exposure. The secondary structure of mutant bacteriocin LD3UVM921 was without alpha helix, 38.54 % beta-strand and 61.45 % random coil compared to 7.27 % alpha helix, 33.63 % beta-strand, and 59.09 % random coil in wild-type. The molecular docking analysis indicated higher binding affinity of mutant bacteriocin LD3UVM921 with Man-PTS compared to wild-type leading to higher bacteriocin activity.

Conclusion

The UV radiation successfully generated alteration in bacteriocin gene and affected its production level. The over-producing mutant of E. hirae LD3 may be used in food and pharmaceutical industries for large scale production of bacteriocin.