Properties of Three Plasmids Isolated From Plant Pathogenic Pseudomonads
Obukowicz, Mark Gerard
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https://hdl.handle.net/2142/70587
Description
Title
Properties of Three Plasmids Isolated From Plant Pathogenic Pseudomonads
Author(s)
Obukowicz, Mark Gerard
Issue Date
1983
Department of Study
Plant Pathology
Discipline
Plant Pathology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Plant Pathology
Abstract
Indigenous plasmids isolated from Pseudomonas tabaci ATCC 11528 (pJP1), P. tabaci BR2 (pBPW1), and P. angulata 45 (pJP30) were labeled with Tn3 using RSF1010::Tn3 as a vector and the host strains were subsequently cured of their Tn3-containing plasmid. Plasmid-containing and respective cured strains produced nearly identical symptoms on host and nonhost plants when serial dilutions of bacteria were injected directly into leaf tissue. Also, cured and plasmid-containing isolates of P. tabaci 11528 and P. tabaci BR2 produced approximately the same amount of tabtoxin. These data indicate that pJP1, pBPW1, and pJP30 do not encode genes essential for pathogenicity and/or tabtoxin synthesis.
The cryptic plasmids pJP1, pBPW1, and pJP30 were then examined for four possible plasmid-encoded functions; (1) conjugative ability, (2) synthesis of Pseudomonas phage-specific receptor(s), (3) carbon compound catabolism, and (4) a competitive advantage conferred to host bacteria in their ability to multiply on leaf surfaces. Results showed that; (1) pBPW1::Tn3 mobilized itself and RSF1010 at high frequencies into P. mellea recipients. Mobilization of each plasmid was a separate event in that pBPW1::Tn3 and RSF1010 were found singly in nearly half of the transconjugants. No detectable homology by Southern blotting was found between pBPW1 and RSF1010 in donors prior to conjugation or in recipients containing both plasmids after conjugation. These data indicated that pBPW1 and RSF1010 did not recombine during mobilization. Rather, pBPW1 donates RSF1010 by a yet unknown mechanism. (2) pJP1 and pJP30, like pBPW1, are conjugative and pJP1 is also able to mobilize RSF1010. (3) pBPW1 encodes phage receptor(s) for the phages PRD1 and PR3. (4) No differences in carbon compound utilization by plasmid-containing and cured strains were detected. (5) No differences in epiphytic growth of cured and plasmid-containing strains of P. tabaci 11528 or P. tabaci BR2 on host and nonhost plants were observed.
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