Antibacterial Activity of Two Metabolites Isolated From Endophytic Bacteria Bacillus velezensis Ea73 in Ageratina adenophora

Zhihua Ren; Lei Xie; Samuel Kumi Okyere; Juan Wen; Yinan Ran; Xiang Nong; Yanchun Hu

doi:10.3389/fmicb.2022.860009

Antibacterial Activity of Two Metabolites Isolated From Endophytic Bacteria Bacillus velezensis Ea73 in Ageratina adenophora

Front Microbiol. 2022 May 6:13:860009. doi: 10.3389/fmicb.2022.860009. eCollection 2022.

Authors

Zhihua Ren¹, Lei Xie¹, Samuel Kumi Okyere¹, Juan Wen¹, Yinan Ran¹, Xiang Nong², Yanchun Hu¹

Affiliations

¹ Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Yaan, China.
² College of Life Science, Leshan Normal University, Leshan, China.

Abstract

Ageratina adenophora, as an invasive and poisonous weed, seriously affects the ecological diversity and development of animal husbandry. Weed management practitioners have reported that it is very difficult to control A. adenophora invasion. In recent years, many researchers have focused on harnessing the endophytes of the plant as a useful resource for the development of pharmacological products for human and animal use. This study was performed to identify endophytes with antibacterial properties from A. adenophora. Agar well diffusion method and 16S rRNA gene sequencing technique were used to screen and identify endophytes with antibacterial activity. The response surface methodology and prep- high-performance liquid chromatography were used to determine the optimizing fermentation conditions and isolate secondary metabolites, respectively. UV-visible spectroscopy, infrared spectroscopy, nuclear magnetic resonance, and high-resolution mass spectrum were used to determine the structures of the isolated metabolites. From the experiment, we isolated a strain of Bacillus velezensis Ea73 (GenBank no. MZ540895) with broad-spectrum antibacterial activity. We also observed that the zone of inhibition of B. velezensis Ea73 against Staphylococcus aureus was the largest when fermentation broth contained 6.55 g/L yeast extract, 6.61 g/L peptone, 20.00 g/L NaCl at broth conditions of 7.95 pH, 51.04 h harvest time, and a temperature of 27.97°C. Two antibacterial peptides, Cyclo (L-Pro-L-Val) and Cyclo (L-Leu-L-Pro), were successfully extracted from B. velezensis Ea73. These two peptides exhibited mild inhibition against S. aureus and Escherichia coli. Therefore, we isolated B. velezensis Ea73 with antibacterial activity from A. adenophora. Hence, its metabolites, Cyclo (L-Pro-L-Val) and Cyclo (L-Leu-L-Pro), could further be developed as a substitute for human and animal antibiotics.

Keywords: Ageratina adenophora; Bacillus velezensis Ea73; antibacterial compound; endophytes; secondary metabolites.