AUTHOR=Ren Zhihua , Xie Lei , Okyere Samuel Kumi , Wen Juan , Ran Yinan , Nong Xiang , Hu Yanchun 

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

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.860009

DOI=10.3389/fmicb.2022.860009

ISSN=1664-302X

ABSTRACT=<p><italic>Ageratina adenophora</italic>, 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 <italic>A. adenophora</italic> 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 <italic>A. adenophora</italic>. 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 <italic>Bacillus velezensis</italic> Ea73 (GenBank no. MZ540895) with broad-spectrum antibacterial activity. We also observed that the zone of inhibition of <italic>B. velezensis</italic> Ea73 against <italic>Staphylococcus aureus</italic> 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 (<italic>L</italic>-Pro-<italic>L</italic>-Val) and Cyclo (<italic>L</italic>-Leu-<italic>L</italic>-Pro), were successfully extracted from <italic>B. velezensis</italic> Ea73. These two peptides exhibited mild inhibition against <italic>S. aureus</italic> and <italic>Escherichia coli</italic>. Therefore, we isolated <italic>B. velezensis</italic> Ea73 with antibacterial activity from <italic>A. adenophora</italic>. Hence, its metabolites, Cyclo (<italic>L</italic>-Pro-<italic>L</italic>-Val) and Cyclo (<italic>L</italic>-Leu-<italic>L</italic>-Pro), could further be developed as a substitute for human and animal antibiotics.</p>