Screening of Lysobacter enzymogenes L-43 and Preliminary Identification of the Antibacterial Substances
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Abstract:
A bacterial strain exhibiting antimicrobial activity was identified in farmland soil and screened using the transparent circle and agar diffusion methods. The strain was identified through morphological observation, physical and chemical analysis, and 16S rDNA sequence alignment, and the antimicrobial substances produced by the strain were identified using extracellular enzyme activity assay, protease hydrolysis, ammonium sulfate precipitation, membrane analysis, and stability analysis. The results showed that the identified strain was Lysobacter enzymogenes L-43, which demonstrated good antibacterial activity and no hemolysis. The antibacterial substances produced by L. enzymogenes L-43 had a broad antimicrobial spectrum and maintained a good inhibitory effect on Gram-positive bacteria. The diameter of the inhibition zone exceeded 10 mm. The antibacterial substances had no lysozyme activity and did not contain hydrogen peroxide. They were sensitive to protease E, protease K, pepsin, and trypsin, and the antibacterial activity recovery rate was 73.43%~79.00%. After membrane analysis, when the molecular weight cut-off of the dialysis bag was 3 500 u and 10 000 u, the antibacterial activity recovery rates were 93.43% and 59.82%, respectively. It was preliminarily determined that the antibacterial substances were mainly polypeptides with molecular weights between 3 500~10 000 u. The substances showed good thermal, acid-base, metal ion, chemical reagent, and storage stability, and the antibacterial activity recovery rate was 85.66% after treatment at 121 ℃ for 30 min. The antibacterial recovery rate was higher than 80% at pH 2~10, further confirming that the antibacterial substance was a polypeptide. In conclusion, the antibacterial substances produced by L. enzymogenes L-43 are stable peptides with a broad antibacterial spectrum. The findings of this study provide a foundation for the development of antibacterial strains and their metabolites.
