The "sexually deceptive" orchid Chiloglottis trapeziformis attracts males of its pollinator species, the thynnine wasp Neozeleboria cryptoides, by emitting a unique volatile compound, 2-ethyl-5-propylcyclohexan-1,3-dione, which is also produced by female wasps as a male-attracting sex pheromone.

Sphingolipids desaturated at the ⌬4-position are important signaling molecules in many eukaryotic organisms, including mammals. In a bioinformatics approach, we now identified a new family of protein sequences from animals, plants, and fungi and characterized these sequences biochemically by expression in Saccharomyces cerevisiae. This resulted in the identification of the enzyme sphingolipid ⌬4-desaturase (dihydroceramide desaturase) from Homo sapiens, Mus musculus, Drosophila melanogaster, and Candida albicans, in addition to a bifunctional sphingolipid ⌬4-desaturase/C-4-hydroxylase from M. musculus. Among the sequences investigated are the Homo sapiens membrane lipid desaturase, the M. musculus degenerative spermatocyte, and the Drosophila melanogaster degenerative spermatocyte proteins. During spermatogenesis, but not oogenesis of des mutant flies, both cell cycle and spermatid differentiation are specifically blocked at the entry into the first meiotic division, leading to male sterility. This mutant phenotype can be restored to wild-type by complementation with a functional copy of the des gene (Endo, K., Akiyama, T., Kobayashi S., and Okada, M. (1996) Mol. Gen. Genet. 253, 157-165). These results suggest that ⌬4-desaturated sphingolipids provide an early signal necessary to trigger the entry into both meiotic and spermatid differentiation pathways during Drosophila spermatogenesis.

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Orchids employing sexual deceit attract males of their pollinator species through specific volatile signals that mimic female-released sex pheromones. One of these signals proved to be 2-ethyl-5-propylcyclohexan-1,3-dione (chiloglottone1), a new natural product that was shown to be most important in the relations between orchids of the genus Chiloglottis, native to Australia, and corresponding pollinator species. Systematic investigations on the mass spectrometric fragmentation pattern of 2,5-dialkylcyclohexan-1,3-diones identified key ions providing information about the structures of the substituents at positions 2 and 5. Results enabled us to identify 2-ethyl-5-pentylcyclohexan-1,3-dione (chiloglottone2) and 2-butyl-5-methylcyclohexan-1,3-dione (chiloglottone3) as new natural products that play a decisive role in the pollination syndrome of some Chiloglottis species. During field bioassays, pure synthetic samples of chiloglottone1-3 or mixtures thereof proved to be attractive to the corresponding orchid pollinators. Because of their likely biogenesis from ubiquitous fatty acid precursors, 2,5-dialkylcyclohexan-1,3-diones may represent a hitherto overlooked, widespread class of natural products.2-butyl-5-methylcyclohexan-1,3-dione ͉ 2-ethyl-5-pentylcyclohexan-1,3-dione ͉ Chiloglottis ͉ semiochemical ͉ mass spectrometry

The thermophilic aerobic bacterium Bacillus thermoleovorans Hamburg 2 grows at 60°C on naphthalene as the sole source of carbon and energy. In batch cultures, an effective substrate degradation was observed. The carbon balance, including naphthalene, metabolites, biomass, and CO 2 , was determined by the application of [1-13 C]naphthalene. The incorporation of naphthalene-derived carbon into the bulk biomass as well as into specified biomass fractions such as fatty acids and amino acids was confirmed by coupled gas chromatographymass spectrometry (GC-MS) and isotope analyses. Metabolites were characterized by GC-MS; the established structures allow tracing the degradation pathway under thermophilic conditions. Apart from typical metabolites of naphthalene degradation known from mesophiles, intermediates such as 2,3-dihydroxynaphthalene, 2-carboxycinnamic acid, and phthalic and benzoic acid were identified for the pathway of this bacterium. These compounds indicate that naphthalene degradation by the thermophilic B. thermoleovorans differs from the known pathways found for mesophilic bacteria.The naphthalene metabolism of mesophilic microorganisms under aerobic conditions has been intensely investigated, and detailed information has been presented on degradation rates, metabolic pathways, and the involved enzymes (7,8,11,25). In contrast, little is known about the metabolism of naphthalene or other polycyclic aromatic hydrocarbons (PAH) by thermophilic bacteria. Several studies on the growth of thermophilic microorganisms on aromatic compounds such as benzoic acid, cresols, or phenols have been carried out; however, respective degradation pathways are largely unresearched (1,4,19,20). The degradation of xenobiotics by thermophilic microorganisms provides crucial advantages compared to mesophilic organisms, especially when they are applied in biotechnological processes. Limited bioavailability as a result of the low water solubility of hydrophobic contaminants may be overcome due to a higher water solubility at elevated temperatures. The water solubility of naphthalene, for example, rises from 30 mg liter Ϫ1 at 20°C to 130 mg liter Ϫ1 at 60°C (26). Moreover, diffusion rates increase at higher temperatures with an additional positive impact on bioavailability.The bacteria applied in this degradation study were isolated from a compost consisting of wooden ties treated with lignite tar. They were able to utilize naphthalene as a sole source of carbon and energy. Stable isotope labeled [1-13 C]naphthalene was used as a model contaminant. The fate of naphthalene was traced by means of the technique of 13 C isotope analysis, which has been successfully applied to trace metabolic pathways (3,18,22). Stable isotope labeling enabled us to trace quantitatively the transformation of the xenobiotic carbon into specific fractions such as CO 2 , biomass, and metabolites. Moreover, the incorporation of the xenobiotic carbon into the bacterial fatty and amino acid fraction was determined on a molecular level. We describe here str...