Characterization of Antifungal Lipopeptide Biosurfactants Produced by Marine Bacterium Bacillus sp. CS30.

Shimei Wu,Zhenxia Sha,Chaomin Sun,Shengnan Zhou,Ge Liu

doi:10.3390/md17040199

Abstract

This study was initiated to screen for marine bacterial agents to biocontrol Magnaporthe grisea, a serious fungal pathogen of cereal crops. A bacterial strain, isolated from the cold seep in deep sea, exhibited strong growth inhibition against M. grisea, and the strain was identified and designated as Bacillus sp. CS30. The corresponding antifungal agents were purified by acidic precipitation, sequential methanol extraction, Sephadex LH-20 chromatography, and reversed phase high-performance liquid chromatography (RP-HPLC), and two antifungal peaks were obtained at the final purification step. After analysis by mass spectrometry (MS) and tandem MS, two purified antifungal agents were deduced to belong to the surfactin family, and designated as surfactin CS30-1 and surfactin CS30-2. Further investigation showed that although the antifungal activity of surfactin CS30-1 is higher than that of surfactin CS30-2, both of them induced the increased generation of reactive oxygen species (ROS) and caused serious damage to the cell wall and cytoplasm, thus leading to the cell death of M. grisea. Our results also show the differences of the antifungal activity and antifungal mechanism of the different surfactin homologs surfactin CS30-1 and surfactin CS30-2, and highlight them as potential promising agents to biocontrol plant diseases caused by M. grisea.

Highlights

With the emerging resistance of pathogens to commonly used antibiotics or fungicides, the discovery and development of new alternative chemicals is of the utmost importance
Due to their amphipathic characteristics, lipopeptides can induce the formation of pore and ion channels in lipid bilayer membranes and cause less pathogen resistance compared with traditional antibiotics or fungicides
In order to obtain potential bacterial strains producing antifungal agents, about 500 marine bacteria were isolated from the sediments of cold seep in deep sea, and their inhibitory activities against the plant pathogenic fungus M. grisea were determined

Summary

Introduction

With the emerging resistance of pathogens to commonly used antibiotics or fungicides, the discovery and development of new alternative chemicals is of the utmost importance. Lipopeptides are natural small cyclic or linear compounds synthesized by various microorganisms, which consist of hydrophobic long alkyl chains and hydrophilic polypeptides [1]. Due to their amphipathic characteristics, lipopeptides can induce the formation of pore and ion channels in lipid bilayer membranes and cause less pathogen resistance compared with traditional antibiotics or fungicides. Lipopeptides are more environment-friendly because of their low toxicity and high biodegradability, and possess high stability towards extreme temperature, pH, and salinity, becoming an alternative to ordinary chemical agents [2,3,4].

Methods

Results

Conclusion