The antibacterial mechanism of phenylacetic acid isolated from Bacillus megaterium L2 against Agrobacterium tumefaciens

PeerJ. 2022 Nov 8:10:e14304. doi: 10.7717/peerj.14304. eCollection 2022.

Abstract

Background: Agrobacterium tumefaciens T-37 can infect grapes and other fruit trees and cause root cancer. Given the pollution and damage of chemical agents to the environment, the use of biological control has become an important area of focus. Bacillus megaterium L2 is a beneficial biocontrol strain isolated and identified in the laboratory, which has a good antibacterial effect on a variety of plant pathogens. The antibacterial metabolites of L2 were separated and purified to obtain a bioactive compound phenylacetic acid (PAA).

Methods: The potential antibacterial mechanism of PAA against A. tumefaciens T-37 strain was determined by relative conductivity, leakage of nucleic acids, proteins, and soluble total sugars, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and reactive oxygen species (ROS).

Results: PAA showed good antibacterial activity against strain A. tumefaciens T-37 with IC50 of 0.8038 mg/mL. Our data suggested that after treatment with PAA, the relative conductivity, nucleic acid, protein, and total soluble sugar of T-37 were increased significantly compared with the chloramphenicol treatment group and the negative treatment group. The total protein synthesis of T-37 cells was inhibited, the consumption of phosphorus decreased with the increase of incubation time, and the content of ROS was significantly higher than that in the negative treatment group. Meanwhile, the activity of two key enzymes (MDH and SDH) involved in the tricarboxylic acid cycle (TCA cycle) decreased. In addition, T-37 cells were found to be damaged by scanning electron microscopy observation. Our results showed that PAA can destroy cell membrane integrity, damage cell structures, affect cell metabolism, and inhibit protein synthesis to exert an antibacterial effect.

Conclusions: We concluded that the mechanism of action of the PAA against strain T-37 might be described as PAA exerting antibacterial activity by affecting cell metabolism, inhibiting protein synthesis, and destroying cell membrane integrity and cell ultrastructure. Therefore, PAA has a promising application prospect in the prevention and treatment of root cancer disease caused by A. tumefaciens.

Keywords: Agrobacterium tumefaciens; Antibacterial mechanism; Bacillus megaterium; Metabolite; Phenylacetic acid.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agrobacterium tumefaciens
  • Anti-Bacterial Agents / pharmacology
  • Bacillus megaterium* / metabolism
  • Phenylacetates / metabolism
  • Reactive Oxygen Species / metabolism
  • Solanum lycopersicum*

Substances

  • Reactive Oxygen Species
  • Anti-Bacterial Agents
  • phenylacetic acid
  • Phenylacetates

Grants and funding

This work was supported by the Guizhou Province High-level Innovative Talent Project (Qiankehe Platform Talent-GCC[2022]027-1), the Science and Technology Project of Guizhou Province (grant number [2021]193); the National Natural Science Foundation of China (grant numbers 31660533, 31460486), the Science and Technology Project of Guizhou Province (grant number [2017]5613); and the Modern Industrial Technology System for Chinese medicinal materials in Guizhou Province. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.