Epigenetic patterns in Atlantic herring (Clupea harengus): Temperature and photoperiod as environmental stressors during larval development.

Understanding the molecular mechanisms underlying individual responses to environmental changes is crucial for species conservation and management. Pelagic fishes including Atlantic herring (Clupea harengus) are of particular interest because of their key ecological and economic roles and their susceptibility to a changing ocean from global warming. Temperature and photoperiod have been linked with spawning time and location in adult herring, but no study has thus far investigated the role of environmental factors on gene regulation during the vulnerable early developmental stages. Here, we examine DNA methylation patterns of larval herring bred under two temperatures (11°C and 13°C) and photoperiod (6 and 12 h) regimes in a 2 × 2 factorial design. We found consistently high levels of global methylation across all individuals and a decline in global methylation with increased developmental stage that was more pronounced at 13°C (p ≤ 0.007) than at 11°C (p ≥ 0.21). Most of the differentially methylated sites were in exon and promoter regions for genes linked to metabolism and development, some of which were hypermethylated at higher temperature. These results demonstrate the important role of DNA methylation during larval development and suggest that this molecular mechanism might be key in regulating early-stage responses to environmental stressors in Atlantic herring.

Production of chlorflavonin, an antifungal metabolite of Aspergillus candidus.

Production of chlorflavonin, a new antifungal antibiotic, by strains of Aspergillus candidus is described. Two wild strains of the fungus had distinctly different chlorflavonin-producing capabilities. One strain produced 25 mug of chlorflavonin per ml per 4 to 5 days in a pilot scale fermentor with stirring, using a medium containing corn steep liquor and glucose. Production of antibiotic was favored by high rates of agitation-aeration. Crude chlorflavonin was extracted from the whole brew with a hydrocarbon solvent and then purified by recrystallization from benzene and petroleum ether. The overall yield from fermentation brew to pure product was 50%.