Pseudomonas Fluorescens Strain A506


Book Description

"Health Canada's Pest Management Regulatory Agency (PMRA), under the authority of the Pest Control Products Act (PCPA) and Regulations, has granted conditional registrations for the sale and use of Pseudomonas fluorescens Strain A506 and Blightban A506, containing the technical grade active ingredient Pseudomonas fluorescens strain A506, to control fire blight on apples and pears. This Overview describes the key points of the evaluation, while the Science Evaluation provides detailed technical information on the human health, environmental and value assessments of Pseudomonas fluorescens Strain A506 and Blightban A506"--Document.







Effect of Iron on Biological Control of Fire Blight by Pseudomonas Fluorescens A506


Book Description

Competitive exclusion has been the mechanism hypothesized to account for the biological control of fire blight disease of pear and apple by the bacterium Pseudomonas fluorescens A506 (A506). Recent laboratory assays demonstrated, however, that A506 produces an antibiotic that is toxic to the fire blight pathogen, Erwinia amylovora, when cultured on media amended with iron (Fe2 or Fe+3). This study investigated this iron-dependent antibiosis by A506 by: 1) examining bioavailability of iron to A506 on blossom surfaces, 2) mutagenizing A506 to disrupt genes involved in antibiotic production, and 3) evaluating suppression of fire blight by A506 when co-treated with an iron chelate (FeEDDHA). Bioavailability of iron on blossoms was investigated with an iron biosensor [iron-regulated promoter (pvd) fused to an ice nucleation reporter gene (inaZ)] in A506. A506 (pvd-inaZ) expressed high ice nucleation activity (INA) on blossoms indicating a low-iron environment unlikely to induce antibiosis by A506. Spraying blossoms with FeEDDHA at concentrations e".1 mM significantly suppressed INA by A506 (pvd-inaZ). Transposon mutagenesis was used to generate and select mutants of A506 exhibiting altered antibiotic production profiles. One antibiotic-deficient mutant, A506 Ant−, was recovered; this mutant showed reduced epiphytic fitness on blossoms of apple and pear trees compared to the parent stain, A506. Another mutant, A506 Ant+, lost the characteristic fluorescent phenotype and exhibited iron-independent antibiotic production in defined culture media. A506 Ant+ established high populations on blossoms of apple and pear trees, similar to populations attained by A506, and reduced incidence of fire blight between 20 to 40%, levels comparable to A506 in orchard trials. In orchard trials, A506 was co-treated with FeEDDHA and fire blight suppression was evaluated. Bacterial strains established high populations on blossoms when co-treated with 0.1 mM FeEDDHA or in water. Significantly enhanced suppression of fire blight incidence by antibiotic producing strains of A506 amended with 0.1 mM FeEDDHA was observed in 2 of 5 trials, providing some evidence that iron-induced antibiosis can be a contributing mechanism in disease control. Lack of disease control by the antibiotic deficient strain, A506 GacS, and by 0.1 mM FeEDDHA alone added support to this hypothesis.




Genomics-enabled Exploration of Insect Toxicity in the Pseudomonas Fluorescens Group


Book Description

Pseudomonas is a diverse genus of Gamma proteobacteria that are ubiquitous in the natural environment, including soil, water, plant surfaces, and animals. The Pseudomonas fluorescens group is a diverse collection of seven subgroups and more than 50 named species. This group is known for their production of a variety of secondary metabolites and antimicrobial compounds that contribute to biological control of plant diseases. Recently, they also have been shown to relay both oral and injectable insect lethality by mechanisms that are unknown. The first objective of this study was to determine if ten fully sequenced strains in the P. fluorescens group are lethal to insects, using larvae of the tobacco hornworm (Manduca sexta) as a model system. A second objective was to characterize putative insect toxin complex (Tc) genes in the genomes of the ten strains. Additionally, genes encoding putative insect toxins (Tc) and possible modes of immunosuppression (the AprA metalloprotease and GacS/GacA regulatory system) were examined for their contribution to lethality of one strain of P. fluorescens. I established that six of ten strains representing diverse lineages of the P. fluorescens group exhibited injectable lethality to larvae of M. sexta, while four of the strains exhibited no significant lethality. Seven strains of the P. fluorescens group had Tc gene clusters. These clusters were categorized into six distinct types, based on the organization, genomic context, G+C content, and phylogeny of the Tc genes. One of the types included genes from strain A506, which was selected for further study because of its injectable lethality towards M. sexta, and its importance as a model strain in studies of phyllosphere microbial ecology and as a commercial biological control agent. Of the genes (aprA, gacS and tcaABC-tccC) evaluated for their roles in insect lethality, the tcaABC-tccC cluster had the greatest effect on insect lethality by A506. This study provides the first evidence for a significant effect of a Tc cluster on insect lethality by a Pseudomonas species. Nevertheless, none of the genes evaluated were fully responsible for the injectable lethality caused by A506, indicating that loci other than those evaluated here contribute to insect toxicity by this strain.













Pseudomonas syringae and related pathogens


Book Description

This volume mainly reports on new and recent advancements on different aspects of Pseudomonas syringae, a plant pathogenic bacterial species that include a high number of pathogens of important crops, which is an interesting model organism in plant pathology. In addition some related fluorescent Pseudomonas spp., responsible of new and emerging diseases, as well as some pathogens previously included in the above genus and now classified in the genera Ralstonia, Acidovorax are also considered. The tremendous recent advancements on: the ecology and epidemiology and, in particular, the adaptation of P. syringae to stresses and adverse environmental conditions; the function and regulation of genes involved in the production of phytotoxins and on their mechanism of action in the interaction with the host cells; the structure, function and regulation of type three secretion system (TTSS) and the transport of the effectors proteins in the host cells; the possibility to control diseases through the induction of the systemic acquired resistance (SAR); the development of molecular techniques for the highly specific and sensible identification and detection of pathogens; the determination of the causal agents of new and emerging diseases as well the classification of the different pathovars of P. syringae; are reported in 76 chapters cured by leading scientist in the respective fields.




Phytopathogenic Bacteria and Plant Diseases


Book Description

The field of Phytobacteriology is rapidly advancing and changing, because of recent advances in genomics and molecular plant pathology, but also due to the global spread of bacterial plant diseases and the emergence of new bacterial diseases. So, there is a need to integrate understanding of bacterial taxonomy, genomics, and basic plant pathology that reflects state-of-the-art knowledge about plant-disease mechanisms. This book describes seventy specific bacterial plant diseases and presents up-to-date classification of plant pathogenic bacteria. It would be of great help for scientists and researchers in conducting research on ongoing projects or formulation of new research projects. The book will also serve as a text book for advanced undergraduate and postgraduate students of disciplines of Phytobacteriology and Plant Pathology. Contains latest and updated information of plant pathogenic bacteria till December 2018 Describes seventy specific bacterial diseases Presents classification of the bacteria and associated nomenclature based on Bergey’s Manual Systematic Bacteriology and International Journal of Systematic and Evolutionary Microbiology Discusses practical and thoroughly tested disease management strategies that would help in controlling enormous losses caused by these plant diseases Reviews role of Type I-VI secretion systems and peptide- or protein-containing toxins produced by bacterial plant pathogens Briefs about plants and plant products that act as carriers of human enteric bacterial pathogens, like emphasizing role of seed sprouts as a common vehicle in causing food-borne illness Dr B. S. Thind was ex-Professor-cum-Head, Department of Plant Pathology, Punjab Agricultural University Ludhiana, India. He has 34 years of experience in teaching, research, and transfer of technology. He has conducted research investigations on bacterial blight of rice, bacterial stalk rot of maize, bacterial blight of cowpea, bacterial leaf spot of green gram, bacterial leaf spot of chillies and bacterial soft rot of potatoes. He also acted as Principal Investigator of two ICAR-funded research schemes entitled, "Detection and control of phytopathogenic bacteria from cowpea and mungbean seeds from 1981 to 1986 and "Perpetuation, variability, and control of Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight of rice" from 1989 to 1993, and also of a DST funded research scheme "Biological control of bacterial blight, sheath blight, sheath rot, and brown leaf spot of rice" from 1999 to 2002. He also authored a manual entitled, "Plant Bacteriology" and a text book entitled, "Phytopathogenic Procaryotes and Plant Diseases" published by Scientific Publishers (India). He is Life member of Indian Phytopathological Society, Indian Society of Plant Pathologists, Indian Society of Mycology and Plant Pathology, and Indian Science Congress Association.




Nonculturable Microorganisms in the Environment


Book Description

This text on viable but non-culturable organisms provides information on topics including: morphological changes; the role of membranes; genetics and genetic regulation; molecular methods for detection; as well as survival dominancy and related phenomena. The main purpose of the text is to elucidate the phenomenon and to distinguish it from other seemingly related but different phenomena such as spore formation, dormancy, starvation, and injury. It covers a cross section of morphology, metabolism, genetics, ecology and epidemiology.