Isolation and characterization of Priestia megaterium KD7 for the biological control of pear fire blight

Abstract

Erwinia amylovora is a plant pathogen that causes fire blight disease in Rosaceous plants, such as pear and apple. To develop an effective biocontrol method to suppress E. amylovora, a total of 16 bacteria were isolated from pear orchard soil in China and screened for antagonistic activity in vitro. Among them, 9 isolates that exhibited antagonistic activity against E. amylovora were identified, including Bacillus atrophaeus, Priestia megaterium (previously known as Bacillus megaterium) and Serratia marcescens based on the partial 16S rDNA sequence analysis and similarity search. The plate confrontation experiments showed that strain 8 (P. megaterium strain KD7) had strong antagonistic activity against E. amylovora. The methanolic extract from cell-free supernatant of strain KD7 displayed high antibacterial activities against E. amylovora. Furthermore, the active compounds of strain KD7 were separated by thin layer chromatography (TLC) and the amino acids were detected by the presence of a spot with retention factor (Rf) of 0.71. Next, three lipopeptides were identified with high-resolution mass spectrometry (HRMS), including C13-surfactin [M+H]+ at m/z 1008.14, C15-surfactin [M+H]+ at m/z 1036.50, and C14-iturin A [M+H]+ at m/z 1043.17. Strain KD7 showed multiple antibiotic resistance, such as ampicillin, erythromycin, penicillin and tetracycline. The detached pear leaves, twigs and fruits assay showed that both protective and curative action with strain KD7 had the ability to decrease the development of fire blight. Taken together, P. megaterium strain KD7 is a potential effective biocontrol agent against fire blight.

Screening for Novel Beneficial Environmental Bacteria for an Antagonism-Based Erwinia amylovora Biological Control

“…The importance of finding an environmentally friendly and effective control mechanism against fire blight due to the lack of efficient phytosanitary control measures to stop its dissemination makes E. amylovora a pathogen of great concern worldwide [ 55 ]. In recent years, biological control with microbial antagonists has been considered a powerful and eco-friendly alternative [ 56 ]. In this panorama, the aim of this work was to evaluate the potential antagonistic activity of a collection of environmental bacterial isolates against E. amylovora .…”

“…The efficacy of some antagonistic bacteria for the control of fire blight in detached loquat and/or pear fruit has been demonstrated in recent studies with plant-associated bacterial species [ 40 ] and, more recently, with a strain of Priestia megaterium isolated from a pear orchard [ 56 ]. However, neither Paenarthrobacter aurescens , P. nicotinovorans nor Pseudomonas moraviensis from fire blight-free Mediterranean environments have been described so far as potential biocontrol agents of E. amylovora .…”

Bacterial Lipopeptides Are Effective against Pear Fire Blight

“…We used as standard strains of E. amylovora C1 isolated by our research group [25]. To nurture and propagate E. amylovora cultures, we employed nutrient agar (NA), which consists of beef extract, peptone, agar, and sodium chloride, with a pH range maintained between 7.2 and 7.4 [26].…”

Isolation and Characterization of a Lytic Bacteriophage RH-42-1 of Erwinia amylovora from Orchard Soil in China

“…formulation “Blight BanC9-1” [ 7 ], the Bacillus subtilis QST713 formulation “Serenade” [ 8 ], and BD170 [ 9 ] have been applied on a certain scale, showing comparable efficacy to antibiotics under ideal conditions. In China, a group of antagonistic strains exhibiting good activity against fire blight bacteria has been screened, but they are still in the research or trial phase and have not been registered for use [ 10 ].…”