Identification and Pathogenicity Test of Bacterial Symbionts from an Entomopathogenic Oscheius. Alhussaini, Abdulrahman A.
dc.contributor.department Tropical Plant Pathology 2019-05-28T20:42:53Z 2019-05-28T20:42:53Z 2018-08
dc.title Identification and Pathogenicity Test of Bacterial Symbionts from an Entomopathogenic Oscheius.
dc.type Thesis
dcterms.abstract The main objectives of this thesis research were to examine Oscheius nematodes for its 1) associated bacteria (to be identified), 2) associated bacteria pathogenicity on insects, and 3) status as entomopathogenic nematodes. Nematodes are unsegmented pseudocoelomic roundworms that exist in all environments and occupy all trophic levels including of bacterial-feeders, predators, and parasites. Oscheius spp. are clearly bacterial-feeding nematodes but some isolates have behaviors with entomopathogenicity. A series of tests were conducted to isolate, identify, and determine insect toxicity of bacteria associated with several Hawaii isolates of Oscheius sp. Bacteria were isolated from Oscheius isolates BI 1a, BI 12a, OJ 4a, OJ 5b and compared with that of a well-recognized entomopathogenic nematode, Steinernema feltiae MG14. Eleven bacterial isolates were identified and isolated from four different Oscheius populations through DNA sequencing. Enterobacter genus was most commonly isolated followed by Pseudomonas and Enterococcus. Pathogenicity of Serratia sp., Enterococcus sp., and Pseudomonas sp. isolated were evaluated on mealworm (Tenebrio molitor) larvae using two assays: 1) feeding assay on a bacteria-inoculated diet, or 2) directly assay by injecting the bacteria into the hemolymph. All assays showed that these three bacteria isolates were pathogenic to the mealworms within 48 hour after the feeding or injection. Among the three bacteria isolates tested, Pseudomonas was more lethal to mealworms than Serratia or Enterococcus in both assays. Injection the bacteria at 108 cfu/ml increased their pathogenicity compared to 102-106 cfu/ml regardless of the bacteria species. The association between the entomotoxic bacteria and the nematode confirms the entomopathogenic nature of these isolates of Oscheius from Hawaii. The implication of the findings from this study showed that Oscheius indigenous to Hawaii can offer effective biological control against some insects without having to go through importation regulation and would be a good alternatives to conventional insecticides that are harmful to the environment.
dcterms.description M.S. Thesis. University of Hawaiʻi at Mānoa 2018.
dcterms.language eng
dcterms.publisher University of Hawaiʻi at Mānoa
dcterms.rights All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
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