Date of Award:

5-1-1996

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Jon Y. Takemoto

Committee

Jon Y. Takemoto

Committee

Bradley R. Kropp

Committee

Lance C. Seefeldt

Abstract

Cyclic lipodepsipeptides (CLPs), a new class of antifungal agents, are produced by Pseudomonas syringae pv. syringae. To find novel CLP members, bacterial fluorescent isolates from different plant sources were screened for CLP biosynthetic genes syrB and syrD using a polymerase chain reaction (PCR) and Southern blot analyses. A positive isolate, strain C3, isolated from a cherry tree was virulent on immature cherry fruits, possessed the hypersensitivity/pathogenicity gene, hrpZ, and was grown in supplemented potato broth. Purification of a CLP from strain C3 was performed by acetone extraction, XAD-2 column chromatography, and reversed-phase high performance liquid chromatography (HPLC). HPLC fractions were tested for antifungal activity against Rhodotorula pilimanae. The material in the most active fractions did not co-chromatograph with the known CLPs. A molecular mass of 1151 and amino acid analyses revealed that the compound (CLP-C3A) was a novel CLP. CLP-C3A was acid stable and had antifungal activities with minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) ranges of 5- > 100 μg/ml against human fungal pathogens. Its hemolytic activities were less than those of syringomycin-E (SR-E). In summary, a new P. syringae strain C3 was isolated and characterized. CLP-C3A, a novel CLP, was purified and shown to have antifungal activities.

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