Dong‐Chan Oh

Host-microbe symbioses play a critical role in the evolution of biological diversity and complexity. In a notably intricate system, southern pine beetles use symbiotic fungi to help overcome host-tree defenses and to provide nutrition for their larvae. We show that this beetle-fungal mutualism is chemically mediated by a bacterially produced polyunsaturated peroxide. The molecule's selective toxicity toward the beetle's fungal antagonist, combined with the prevalence and localization of its bact

Induction of the production of emericellamides A and B (1, 2), by the marine-derived fungus Emericella sp., was observed during co-culture with the marine actinomycete Salinispora arenicola. The planar structures of these new cyclic depsipeptides, which incorporate 3-hydroxy-2,4-dimethyldecanoic acid and 3-hydroxy-2,4,6-trimethyldodecanoic acid, were assigned by combined chemical and spectral methods. The absolute configurations of the amino acids, and those of the chiral centers on the side cha

[structure: see text] Two structurally novel cyclopenta[a]indene glycosides, cyanosporasides A and B (1 and 2) have been isolated from the culture broth of a new species of the obligate marine actinomycete genus Salinispora. The structures and absolute stereochemistries of these compounds were determined by spectral and chemical methods. The cyanosporasides possess a new 3-keto-pyranohexose sugar as well as a cyano- and chloro-substituted cyclopenta[a]indene ring system. The cyanosporasides are

A mutualist actinomycete of the southern pine beetle, Dendroctonus frontalis, produces a polyene peroxide with pronounced antifungal activity. Its structure, absolute configuration, and biological activity were determined by spectral analysis, chemical modification followed by the modified Mosher method, and growth inhibitory assays, respectively.

A previously unreported 26-membered polyene macrocyclic lactam, sceliphrolactam, was isolated from an actinomycete, Streptomyces sp., associated with the mud dauber, Sceliphron caementarium. Sceliphrolactam's structure was determined by 1D- and 2D-NMR, MS, UV, and IR spectral analysis. Sceliphrolactam displays antifungal activity against amphotericin B-resistant Candida albicans (MIC = 4 μg/mL, 8.3 μM).

Chemical examination of a phylogenetically unique strain of the obligate marine actinomycete Salinispora pacifica led to the discovery of four new polyketides, salinipyrones A and B ( 1, 2) and pacificanones A and B ( 3, 4). These compounds appear to be derived from a mixed-precursor polyketide biosynthesis involving acetate, propionate, and butyrate building blocks. Spectral analysis, employing NMR, IR, UV, and CD methods and chemical derivatization, was used to assign the structures and absolu

Microbial culture conditions in the laboratory, which conventionally involve the cultivation of one strain in one culture vessel, are vastly different from natural microbial environments. Even though perfectly mimicking natural microbial interactions is virtually impossible, the cocultivation of multiple microbial strains is a reasonable strategy to induce the production of secondary metabolites, which enables the discovery of new bioactive natural products. Our coculture of marine <i>Streptomyc

[structure: see text] Two new cyclic peptides, thalassospiramides A and B (1 and 2), were isolated from a new member of the marine alpha-proteobacterium Thalassospira. The thalassospiramides, the structures of which were assigned by combined spectral and chemical methods, bear unusual gamma-amino acids and show immunosuppressive activity in an interleukin-5 production inhibition assay (IC50 = 5 muM for thalassospiramide B).

Alterations in microbial culture conditions may trigger the production of diverse bioactive secondary metabolites. While applying various culture conditions and monitoring secondary metabolite profiles using LC/MS, hormaomycins B and C (1 and 2) were discovered from a marine mudflat-derived actinomycete, Streptomyces sp., collected in Mohang, Korea. The planar structures of the hormaomycins, which bear structurally-unique units, such as 4-(Z)-propenylproline, 3-(2-nitrocyclopropyl)alanine, 5-chl

In this paper, we consider resource allocation in femtocell networks to maximize the throughput while minimizing interference to macro-cell users nearby. This can be achieved by dynamically allocating the spectrum resource in a cognitive radio way of avoiding the use of spectrum resources occupied by macro-users nearby. The proposed scheme comprises two steps; channel sensing and resource scheduling. The femto base station detects the channel occupation by estimating the energy in sub-channels i

Two new secondary metabolites, arcticoside (1) and C-1027 chromophore-V (2), were isolated along with C-1027 chromophore-III and fijiolides A and B (3-5) from a culture of an Arctic marine actinomycete Streptomyces strain. The chemical structures of 1 and 2 were elucidated through NMR, mass, UV, and IR spectroscopy. The hexose moieties in 1 were determined to be d-glucose from a combination of acid hydrolysis, derivatization, and gas chromatographic analyses. Arcticoside (1) and C-1027 chromopho

Three new secondary metabolites, amycofuran (1), amycocyclopiazonic acid (2), and amycolactam (3), were isolated from the sponge-associated rare actinomycete Amycolatopsis sp. Based on combined spectroscopic analyses, the structures of 1-3 were determined to be a new benzofuran glycoside and new indole alkaloids related to cyclopiazonic acids, a class that has previously only been reported in fungi. The absolute configurations of 1 and 3 were deduced by ECD calculations, whereas that of 2 was de