Characterization of the Biosynthetic Operon for the Antibacterial Peptide Herbicolin in Pantoea vagans Biocontrol Strain C9-1 and Incidence in Pantoea Species
Abstract:ABSTRACTPantoea vagansC9-1 is a biocontrol strain that produces at least two antibiotics inhibiting the growth ofErwinia amylovora, the causal agent of fire blight disease of pear and apple. One antibiotic, herbicolin I, was purified from culture filtrates ofP. vagansC9-1… Show more
“…The sequencing results showed that the bacterial community included 10 types of pathogenic bacteria, including seven E. cloacae strains, K. oxytoca , 20
E. billingiae , and P. vagan 21 . This study confirmed that pathogenic bacteria exist in the traditional Chinese medicine Shenqu.…”
Shenqu is a fermented product that is widely used in traditional Chinese medicine (TCM) to treat indigestion; however, the microbial strains in the fermentation process are still unknown. The aim of this study was to investigate microbial diversity in Shenqu using different fermentation time periods. DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) profiles indicated that a strain of Pediococcus acidilactici (band 9) is the predominant bacteria during fermentation and that the predominant fungi were uncultured Rhizopus, Aspergillus oryzae, and Rhizopus oryzae. In addition, pathogenic bacteria, such as Enterobacter cloacae, Klebsiella oxytoca, Erwinia billingiae, and Pantoea vagan were detected in Shenqu. DGGE analysis showed that bacterial and fungal diversity declined over the course of fermentation. This determination of the predominant bacterial and fungal strains responsible for fermentation may contribute to further Shenqu research, such as optimization of the fermentation process.
“…The sequencing results showed that the bacterial community included 10 types of pathogenic bacteria, including seven E. cloacae strains, K. oxytoca , 20
E. billingiae , and P. vagan 21 . This study confirmed that pathogenic bacteria exist in the traditional Chinese medicine Shenqu.…”
Shenqu is a fermented product that is widely used in traditional Chinese medicine (TCM) to treat indigestion; however, the microbial strains in the fermentation process are still unknown. The aim of this study was to investigate microbial diversity in Shenqu using different fermentation time periods. DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) profiles indicated that a strain of Pediococcus acidilactici (band 9) is the predominant bacteria during fermentation and that the predominant fungi were uncultured Rhizopus, Aspergillus oryzae, and Rhizopus oryzae. In addition, pathogenic bacteria, such as Enterobacter cloacae, Klebsiella oxytoca, Erwinia billingiae, and Pantoea vagan were detected in Shenqu. DGGE analysis showed that bacterial and fungal diversity declined over the course of fermentation. This determination of the predominant bacterial and fungal strains responsible for fermentation may contribute to further Shenqu research, such as optimization of the fermentation process.
“…genomes was used for determination of the biocontrol-specific genes in P. vagans C9-1 and P. agglomerans E325. As expected for P. vagans C9-1, the herbicolin I and pantocin A gene clusters were indicated as singletons (43,44,107). The antibiotic biosynthesis gene cluster of P. agglomerans E325 was identified from the list of singletons for this strain and …”
Section: Application Of Genomics To Improve Fire Blight Management Bisupporting
The enterobacterial phytopathogen Erwinia amylovora causes fire blight, an invasive disease that threatens a wide range of commercial and ornamental Rosaceae host plants. The response elicited by E. amylovora in its host during disease development is similar to the hypersensitive reaction that typically leads to resistance in an incompatible host-pathogen interaction, yet no gene-for-gene resistance has been described for this host-pathogen system. Comparative genomic analysis has found an unprecedented degree of genetic uniformity among strains of E. amylovora, suggesting that the pathogen has undergone a recent genetic bottleneck. The genome of apple, an important host of E. amylovora, has been sequenced, creating new opportunities for the study of interactions between host and pathogen during fire blight development and for the identification of resistance genes. This review includes recent advances in the genomics of both host and pathogen.
“…P. vagans C9-1 was reported to produce a second antibiotic, called herbicolin I [17], but lately renamed dapdiamide E [27]. The chemical structure was described recently for P. agglomerans 48b/90 with the indication that P. vagans C9-1 also produced this compound [28], but the biosynthetic genes of this antibiotic were not identified.…”
Section: Resultsmentioning
confidence: 99%
“…Plasmid rescue and sequencing of the insertion site in mutant CIR624 indicated that the insertion took place in a hypothetical gene, encoded on pPag2 in a cluster containing several predicted biosynthetic and hypothetical genes. Analysis of the insertions that are present in the proposed dapdiamide E biosynthetic cluster is underway [27].…”
Background
Pantoea vagans is a commercialized biological control agent used against the pome fruit bacterial disease fire blight, caused by Erwinia amylovora. Compared to other biocontrol agents, relatively little is currently known regarding Pantoea genetics. Better understanding of antagonist mechanisms of action and ecological fitness is critical to improving efficacy.Principal FindingsGenome analysis indicated two major factors contribute to biocontrol activity: competition for limiting substrates and antibacterial metabolite production. Pathways for utilization of a broad diversity of sugars and acquisition of iron were identified. Metabolism of sorbitol by P. vagans C9-1 may be a major metabolic feature in biocontrol of fire blight. Biosynthetic genes for the antibacterial peptide pantocin A were found on a chromosomal 28-kb genomic island, and for dapdiamide E on the plasmid pPag2. There was no evidence of potential virulence factors that could enable an animal or phytopathogenic lifestyle and no indication of any genetic-based biosafety risk in the antagonist.ConclusionsIdentifying key determinants contributing to disease suppression allows the development of procedures to follow their expression in planta and the genome sequence contributes to rationale risk assessment regarding the use of the biocontrol strain in agricultural systems.
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