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VIRULENCE MECHANISM OF THE NEMATODE PHASMARHABDITIS HERMAPHRODITA AND ITS ASSOCIATED BACTERIUM MORAXELLA OSLOENSIS TO THE GRAY GARDEN SLUG DEROCERAS RETICULATUM

Tan, Li
http://rave.ohiolink.edu/etdc/view?acc_num=osu1038718955

Abstract Details

2002, Doctor of Philosophy, Ohio State University, Entomology.
Moraxella osloensis, a gram-negative bacterium, is associated with Phasmarhabditis hermaphrodita, a lethal slug-parasitic nematode that has potential for the biocontrol of mollusk pests, especially the gray garden slug Deroceras reticulatum. We discovered that the shell cavity in the posterior mantle region of D. reticulatum served as the main portal of entry for P. hermaphrodita. The nematode is a facultative parasite of the slug and only dauer stage can serve as an infective stage in the natural environment. Aged M. osloensis cultures were pathogenic to D. reticulatum after injection into the shell cavity or hemocoel of the slug. P. hermaphrodita vectors M. osloensis into the shell cavity and the bacterium is the main killing agent in the nematode/bacterium complex. We also discovered that M. osloensis lipopolysaccharide (LPS) was an endotoxin that was active against the slug. Purified M. osloensis LPS had a lethal injection toxicity but no contact or oral toxicity against the slug. Toxicity of M. osloensis LPS resides in the lipid A moiety but not in the polysaccharide moiety. The LPS was a rough-type LPS with an estimated molecular weight of 5,300. Coinjection of galactosamine with the LPS increased its toxicity to D. reticulatum by 2-4 fold. The galactosamine-induced sensitization was reversed completely by uridine. We further discovered that 1 or 2-day M. osloensis cultures were non or less pathogenic whereas 3 to 5-day M. osloensis cultures were more pathogenic to the slug. The average yield of M. osloensis LPS per bacterium did not differ among the 1 to 5-day cultures. However, M. osloensis cells from the 3-day cultures produced more outer membrane proteins than those from the younger or older cultures. The intensity and pattern of M. osloensis aggregation changed with time of culture. Pili-like projections were rarely present on the bacterial surfaces of M. osloensis from 1-day cultures, but reached maximal density in 3-day cultures. The temporal expression of the pili-like projections strongly correlates with the temporal pattern of M. osloensis virulence to D. reticulatum. The changes of M. osloensis pathogenicity against D. reticulatum during culture strongly correlate with structural changes in the bacterial cell wall.
Parwinder Grewal (Advisor)
157 p.
Phasmarhabditis hermaphrodita; Moraxella osloensis; Deroceras reticulatum; lipopolysaccharide; galactosamine; uridine; outer membrane proteins; Pili-like projections

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Citations

  • Tan, L. (2002). VIRULENCE MECHANISM OF THE NEMATODE PHASMARHABDITIS HERMAPHRODITA AND ITS ASSOCIATED BACTERIUM MORAXELLA OSLOENSIS TO THE GRAY GARDEN SLUG DEROCERAS RETICULATUM [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1038718955

    APA Style (7th edition)

  • Tan, Li. VIRULENCE MECHANISM OF THE NEMATODE PHASMARHABDITIS HERMAPHRODITA AND ITS ASSOCIATED BACTERIUM MORAXELLA OSLOENSIS TO THE GRAY GARDEN SLUG DEROCERAS RETICULATUM. 2002. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1038718955.

    MLA Style (8th edition)

  • Tan, Li. "VIRULENCE MECHANISM OF THE NEMATODE PHASMARHABDITIS HERMAPHRODITA AND ITS ASSOCIATED BACTERIUM MORAXELLA OSLOENSIS TO THE GRAY GARDEN SLUG DEROCERAS RETICULATUM." Doctoral dissertation, Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1038718955

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.