Pantoea agglomerans (synonym: Erwinia herbicola) strain Eh318 produces through antibiosis a complex zone of inhibited growth in an overlay seeded with Erwinia amylovora, the causal agent of fire blight. This zone is caused by two antibiotics, named pantocin A and B. Using a genomic library of Eh318, two cosmids, pCPP702 and pCPP704, were identified that conferred on Escherichia coli the ability to inhibit growth of E. amylovora. The two cosmids conferred different antibiotic activities on E. coli DH5␣ and had distinct restriction enzyme profiles. A smaller, antibiotic-conferring DNA segment from each cosmid was cloned. Each subclone was characterized and mutagenized with transposons to generate clones that were deficient in conferring pantocin A and B production, respectively. Mutated subclones were introduced into Eh318 to create three antibioticdefective marker exchange mutants: strain Eh421 (pantocin A deficient); strain Eh439 (pantocin B deficient), and Eh440 (deficient in both pantocins). Cross-hybridization results, restriction maps, and spectrum-ofactivity data using the subclones and marker exchange mutants, supported the presence of two distinct antibiotics, pantocin A and pantocin B, whose biosynthetic genes were present in pCPP702 and pCPP704, respectively. The structure of pantocin A is unknown, whereas that of pantocin B has been determined as (R)-N-[((S)-2-amino-propanoylamino)-methyl]-2-methanesulfonyl-succinamic acid. The two pantocins mainly affect other enteric bacteria, based on limited testing. Pantoea agglomerans or Pantoea dispersa (20), also known asErwinia herbicola (Löhnis) Dye are members of the Enterobacteriaceae and are ubiquitous in nature, inhabiting plants, soil, and water (16,20,21) and animals and humans (16,35). Strains belonging to E. herbicola are members of the E. herbicolaEnterobacter agglomerans cluster; some have been redesignated P. agglomerans and P. dispersa, while others did not fall into either of the two species (20). P. agglomerans and P. dispersa are frequent companions of Erwinia amylovora (Burr.) Winslow et al. the causal agent of the disease fire blight of apple and pear trees (36, 38). There is current interest in P. agglomerans and P. dispersa as biological control agents for fire blight because they are harmless to apple and pear trees and are able to protect them against invasion of the pathogen (4, 29). P. agglomerans strain Eh318, isolated from a symptomless apple stem in New York State, protected immature pear fruits in the laboratory (53) and apple blossoms in controlled environment and orchard tests (5,23,43).Production of antibiotics inhibitory to E. amylovora by several strains of Pantoea spp. seems important for inhibition of E. amylovora in planta (30,45,53). In vitro inhibition of E. amylovora by antibiotics of Pantoea spp. is well documented (24,28,45,47,48). Different strains of P. agglomerans and P. dispersa have different spectra of antimicrobial activity (15,25) and produce different types of inhibition zones against the same indicator organis...

ABSTRACT:The infection of stored apples by the fungus Penicillium expansum causes the contamination of fruits and fruit-derived products with the mycotoxin patulin, which is a major issue in food safety. Fungal attack can be prevented by beneficial microorganisms, so-called biocontrol agents. Previous time-course thin layer chromatography analyses showed that the aerobic incubation of patulin with the biocontrol yeast Rhodosporidium kratochvilovae strain LS11 leads to the disappearance of the mycotoxin spot and the parallel emergence of two new spots, one of which disappears over time. In this work, we analyzed the biodegradation of patulin effected by LS11 through HPLC. The more stable of the two compounds was purified and characterized by nuclear magnetic resonance as desoxypatulinic acid, whose formation was also quantitated in patulin degradation experiments. After R. kratochvilovae LS11 had been incubated in the presence of 13 C-labeled patulin, label was traced to desoxypatulinic acid, thus proving that this compound derives from the metabolization of patulin by the yeast. Desoxypatulinic acid was much less toxic than patulin to human lymphocytes and, in contrast to patulin, did not react in vitro with the thiol-bearing tripeptide glutathione. The lower toxicity of desoxypatulinic acid is proposed to be a consequence of the hydrolysis of the lactone ring and the loss of functional groups that react with thiol groups. The formation of desoxypatulinic acid from patulin represents a novel biodegradation pathway that is also a detoxification process.

f Patulin is a mycotoxin that contaminates pome fruits and derived products worldwide. Basidiomycete yeasts belonging to the subphylum Pucciniomycotina have been identified to have the ability to degrade this molecule efficiently and have been explored through different approaches to understand this degradation process. In this study, Sporobolomyces sp. strain IAM 13481 was found to be able to degrade patulin to form two different breakdown products, desoxypatulinic acid and (Z)-ascladiol. To gain insight into the genetic basis of tolerance and degradation of patulin, more than 3,000 transfer DNA (T-DNA) insertional mutants were generated in strain IAM 13481 and screened for the inability to degrade patulin using a bioassay based on the sensitivity of Escherichia coli to patulin. Thirteen mutants showing reduced growth in the presence of patulin were isolated and further characterized. Genes disrupted in patulin-sensitive mutants included homologs of Saccharomyces cerevisiae YCK2, PAC2, DAL5, and VPS8. The patulin-sensitive mutants also exhibited hypersensitivity to reactive oxygen species as well as genotoxic and cell wall-destabilizing agents, suggesting that the inactivated genes are essential for tolerating and overcoming the initial toxicity of patulin. These results support a model whereby patulin degradation occurs through a multistep process that includes an initial tolerance to patulin that utilizes processes common to other external stresses, followed by two separate pathways for degradation.

The current study was initiated to evaluate the efficacy of physical methods (hot water, aerated steam, electron treatment) and agents of natural origin (resistance inducers, plant derived products, microorganisms) as seed treatments of carrots for control of Alternaria dauci and A. radicina. Control of both Alternaria species by seed treatment with the resistance inducers was generally poor. Results were also Eur J Plant Pathol

Greenhouse trials were carried out in order to test the efficacy of different seed treatments as alternatives to chemicals against Colletotrichum lindemuthianum cause of anthracnose on bean and