Experimental evolution of bet hedging under manipulated environmental uncertainty in Neurospora crassa.

All organisms are faced with environmental uncertainty. Bet-hedging theory expects unpredictable selection to result in the evolution of traits that maximize the geometric-mean fitness even though such traits appear to be detrimental over the shorter term. Despite the centrality of fitness measures to evolutionary analysis, no direct test of the geometric-mean fitness principle exists. Here, we directly distinguish between predictions of competing fitness maximization principles by testing Cohen's 1966 classic bet-hedging model using the fungus Neurospora crassa. The simple prediction is that propagule dormancy will evolve in proportion to the frequency of 'bad' years, whereas the prediction of the alternative arithmetic-mean principle is the evolution of zero dormancy as long as the expectation of a bad year is less than 0.5. Ascospore dormancy fraction in N. crassa was allowed to evolve under five experimental selection regimes that differed in the frequency of unpredictable 'bad years'. Results were consistent with bet-hedging theory: final dormancy fraction in 12 genetic lineages across 88 independently evolving samples was proportional to the frequency of bad years, and evolved both upwards and downwards as predicted from a range of starting dormancy fractions. These findings suggest that selection results in adaptation to variable rather than to expected environments.

Antifungal and antioxidant activities of the phytomedicine pipsissewa, Chimaphila umbellata.

Bioassay-guided fractionation of Chimaphila umbellata (L.) W. Bart (Pyrolaceae) ethanol extracts led to the identification of 2,7-dimethyl-1,4-naphthoquinone (chimaphilin) as the principal antifungal component. The structure of chimaphilin was confirmed by 1H and 13C NMR spectroscopy. The antifungal activity of chimaphilin was evaluated using the microdilution method with Saccharomyces cerevisiae (0.05mg/mL) and the dandruff-associated fungi Malassezia globosa (0.39mg/mL) and Malassezia restricta (0.55mg/mL). Pronounced antioxidant activity of C. umbellata crude extract was also identified using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, suggesting this phytomedicine has an antioxidant function in wound healing. A chemical-genetic profile was completed with chimaphilin using approximately 4700 S. cerevisiae gene deletion mutants. Cellular roles of deleted genes in the most susceptible mutants and secondary assays indicate that the targets for chimaphilin include pathways involved in cell wall biogenesis and transcription.

Phytochemistry and antifungal properties of the newly discovered tree Pleodendron costaricense.

Gas chromatography analysis of the essential oils of leaves and bark collected from the newly discovered tree Pleodendron costaricense identified alpha-pinene, beta-pinene, beta-myrcene, beta-thujene, and beta-caryophyllene as their major constituents. Phytochemical analysis of P. costaricense parts led to the isolation and identification of delta-tocotrienol, beta-sitosterol, four known drimane-type sesquiterpenes, cinnamodial (1), cinnamosmolide (2), polygodial (3), and mukaadial (4), and two new compounds, a drimane-type sesquiterpene, parritadial (5), and an eremophilane-type sesquiterpene, pleodendione (6). Antifungal assays with the two major compounds, 1 and 2, were carried out, and results showed a high activity of 1 against Alternaria alternata (MIC = 3.9 microg/mL), Candida albicans azole-resistant strain D10, and Wangiella dermatitides (MICs = 15.6 microg/mL). Compound 2 showed less potent antifungal activities than 1 but was more effective against Candida albicans azole-resistant strain CN1A (MIC = 23.4 microg/mL) and Pseudallescheria boydii (MIC = 78.1 microg/mL). A combination of the dialdehyde sesquiterpenes with dillapiol showed a synergistic antifungal effect with 1 and an additive effect with 4 and 5.