Pseudomonas syringae: The Pathogen and Epiphyte: Difference between revisions
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<ref name=Hirano>[https://www.annualreviews.org/doi/pdf/10.1146/annurev.py.28.090190.001103]</ref> | <ref name=Hirano>[https://www.annualreviews.org/doi/pdf/10.1146/annurev.py.28.090190.001103]</ref> | ||
== | ==Taxonomy of P. syringae== | ||
Early History of the Genus <br> | |||
<br> | <br>Pseudomonas was first understood to comprise all bacteria characterized as aerobic, Gram-negative rods with chemoorganotrophic metabolisms, and mobility from one or more flagella. This wide association was only recently refined in the late 1800s through comparative analyses of 16S rDNA where the fluorescent, poly-B-hydroxybutyrate negative pseudomonads were grouped under Y-Proteobacteria and the non-fluorescent, poly-B-hydroxybutyrate positive pseudomonads were grouped in the B-Proteobacteria. The Pseudomonas genus is one of the earliest in the Y-Proteobacteria class, where the evolutionally history is founded on hundreds of millions of years spend mostly in aquatic habitats under the absence of highly evolved plants and agriculture (3). With a defined genus, the mid-1900s saw an increase in Pseudomonas species identification beginning with P. mori by Boyer and Lambert. Up until the 1960’s it was thought that a major component of the physiology of pathogenic bacteria must be devoted to pathogenic activity where nutritional and cultural differences must reflect early evolutionary metabolic and genetic differences relating to pathogenicity. Such early species proposals were cited on very minimal morphological, biochemical, and nutritional test along with colony appearance on differing media. Thus, the assumption that specific ecological response involved large components of cell metabolism was generally assumed and thus resulted in an increase of named species as synonyms for the same pathogen. This assumption was soon reconsidered with the origin of the P. syringae complex.<br> | ||
The idea of a P. syringae complex developed to characterize as a single species comprising distinct populations capable of infecting limited ranges of hosts. This idea began with a study of fifteen determinative tests that were considered to differentiate fluorescent plant pathogenic Pseudomonas. Of the fifteen determinative tests, it was concluded that only five tests differentiated five distinct pathogenic species groups. These tests include production of levan, capacity to rot potato, oxidase activity, production of arginine dihydrolase, and hypersensitivity reaction in tobacco (LOPAT). From these tests evolved LOPAT Group I pathogens, representing species that gave negative reactions in oxidase activity, capacity to rot potato, production of arginine dihydroalase, and positive hypersensitivity in tobacco. However, Sands et al. (1970) established the idea that many of the LOPAT Group I species could not be explicitly identified or distinguished phenotypically or through biochemical and nutritional tests. Additional DNA-DNA hybridization studies, performed by Palleroni et al. (1972) and Pecknold and Grogan (1973), determined genomic diversity with LOPAT Group I species but lacked significant results to adequately base taxonomic conclusions. Therefore, with increased confusion among bacterial nomenclature, a general revision took place among the International Committee on the Systematics of Bacteria establishing the development of the Approved Lists of Bacterial Names and the International Standards for Naming Pathovars.<br> | |||
As a consequence of these revision, P. syringae pathovars were established. Prior to the revisions, all LOPAT Group I species were grouped under a single species, P. syringae, as pathovars. However, with further identification the P. syringae complex saw an expansion to include a broad quantity of closely related species. This great diversity paired with phenotypic and genotypic variability is not singular to pathogenicity but is also cited in nutrient utilization patterns, bacteriophage sensitivity, bacteriocin production and sensitivity, ice nucleation activity, toxin production, copper and streptomycin resistance, plasmid profiles, and restriction fragment length polymorphism. (1) | |||
==Section 2== | ==Section 2== | ||
Revision as of 20:43, 5 April 2021
Introduction
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Pseudomonas syringae is responsible for various functions within the microbial community and plays a diverse role in the biology of the phyllo-sphere as a pathogen, epiphyte, and ice nucleus (1). The original strain was isolated in 1902, by van Hall, via diseased lilacs (Syringa vulgaris), directly corresponding to the species designation, syringae. By the early 1970s, nearly 40 stains of the phytopathogenic bacteria were isolated form varying plant species lesions and host specificity became an important criterion used by plant pathologist to differentiate variable species (1). Overall,P. syringae is characterized as an aerobic, Gram-negative, rod-shaped bacterium with polar flagella (1). They do not accumulate poly-B-hydroxybutyrate, but do produce diffusible fluorescent pigments and associate as arginine dihydrolase and oxidase negative (1). Additionally, with many variable strains, Phytobacteriologist have created a system for distinguishing between these bacteria via a species designation “pathovar” (pv.) (1). Also, as a plant-based pathogen known for its epiphytic abilities, P. syringae is also incredibly active in ice-nucleation. (3) With such a wide set of biological interactions and significant contributions to biological systems, understanding the molecular basis of P. syringae is critical and has resulted in P. syringae acting as a model for the study of host-pathogen interactions in various experimental hypotheses. (1) In addition, the abundance of P. syringae in rain, snow, and wild plants has been closely reported and corresponds with studies looking into P. syringae in relation to biochemical traits, pathogenicity and pathogenicity-related factors. (3) In all, P. syringae is an archetype of plant pathogens, an ubiquitous epiphyte with well-studied ecology, whose mechanisms of pathogenicity and evolution have been rigorously investigated (3). With the majority of scientific investigations relating to this bacterium focused on its roles as a plant pathogen, the emergence of P. syringae and ice nucleation (IN) activity is also of critical importance (3). With direct relation to processes in which the role of freezing is critical, investigations have led to the idea of P. syringae having an elaborate history whereby it survives and proliferates in diverse niches in habitats linked to the water cycle (3). Therefore, the complex role of P. syringae within the microbial world can hold significant impacts on various environmental processes and biological systems.
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Taxonomy of P. syringae
Early History of the Genus
Pseudomonas was first understood to comprise all bacteria characterized as aerobic, Gram-negative rods with chemoorganotrophic metabolisms, and mobility from one or more flagella. This wide association was only recently refined in the late 1800s through comparative analyses of 16S rDNA where the fluorescent, poly-B-hydroxybutyrate negative pseudomonads were grouped under Y-Proteobacteria and the non-fluorescent, poly-B-hydroxybutyrate positive pseudomonads were grouped in the B-Proteobacteria. The Pseudomonas genus is one of the earliest in the Y-Proteobacteria class, where the evolutionally history is founded on hundreds of millions of years spend mostly in aquatic habitats under the absence of highly evolved plants and agriculture (3). With a defined genus, the mid-1900s saw an increase in Pseudomonas species identification beginning with P. mori by Boyer and Lambert. Up until the 1960’s it was thought that a major component of the physiology of pathogenic bacteria must be devoted to pathogenic activity where nutritional and cultural differences must reflect early evolutionary metabolic and genetic differences relating to pathogenicity. Such early species proposals were cited on very minimal morphological, biochemical, and nutritional test along with colony appearance on differing media. Thus, the assumption that specific ecological response involved large components of cell metabolism was generally assumed and thus resulted in an increase of named species as synonyms for the same pathogen. This assumption was soon reconsidered with the origin of the P. syringae complex.
The idea of a P. syringae complex developed to characterize as a single species comprising distinct populations capable of infecting limited ranges of hosts. This idea began with a study of fifteen determinative tests that were considered to differentiate fluorescent plant pathogenic Pseudomonas. Of the fifteen determinative tests, it was concluded that only five tests differentiated five distinct pathogenic species groups. These tests include production of levan, capacity to rot potato, oxidase activity, production of arginine dihydrolase, and hypersensitivity reaction in tobacco (LOPAT). From these tests evolved LOPAT Group I pathogens, representing species that gave negative reactions in oxidase activity, capacity to rot potato, production of arginine dihydroalase, and positive hypersensitivity in tobacco. However, Sands et al. (1970) established the idea that many of the LOPAT Group I species could not be explicitly identified or distinguished phenotypically or through biochemical and nutritional tests. Additional DNA-DNA hybridization studies, performed by Palleroni et al. (1972) and Pecknold and Grogan (1973), determined genomic diversity with LOPAT Group I species but lacked significant results to adequately base taxonomic conclusions. Therefore, with increased confusion among bacterial nomenclature, a general revision took place among the International Committee on the Systematics of Bacteria establishing the development of the Approved Lists of Bacterial Names and the International Standards for Naming Pathovars.
As a consequence of these revision, P. syringae pathovars were established. Prior to the revisions, all LOPAT Group I species were grouped under a single species, P. syringae, as pathovars. However, with further identification the P. syringae complex saw an expansion to include a broad quantity of closely related species. This great diversity paired with phenotypic and genotypic variability is not singular to pathogenicity but is also cited in nutrient utilization patterns, bacteriophage sensitivity, bacteriocin production and sensitivity, ice nucleation activity, toxin production, copper and streptomycin resistance, plasmid profiles, and restriction fragment length polymorphism. (1)
Section 2
Include some current research, with at least one figure showing data.
Section 3
Include some current research, with at least one figure showing data.
Section 4
Conclusion
References
[1]
[2]
Authored for BIOL 238 Microbiology, taught by Joan Slonczewski, 2021, Kenyon College.
