Oxygenated perfluorocarbon promotes nematode growth and stress-sensitivityin a two-phase liquid culture system

The nematode, Caenorhabditis elegans, can be grown in liquid culture media supplemented with bacteria as a food source, but growth is limited primaril y by lack of oxygen. A novel two-phase liquid culture system has been devel oped in which the nematodes were grown at an interface between a lower laye r of perfluorocarbon and an upper layer of aqueous S medium containing bact eria. By using degassed perfluorodecalin, nematode growth over 3 days was s lightly less than in S medium controls above a plastic substrate; however, this difference in growth rate was barely significant over five replica run s. By using oxygen-saturated perfluorodecalin, growth over 3 days was signi ficantly enhanced, as compared both to S-medium controls and to cultures ov er degassed perfluorodecalin. This much larger effect is attributable to im proved oxygenation at the interface on which the worms move. Measurements w ith an oxygen electrode suggest that dissolved oxygen concentrations were g reatly depleted in both the perfluorocarbon and aqueous layers after 24 h. However, during standard 7-h toxicity tests in aqueous media, an underlying layer of oxygenated perfluorocarbon significantly enhanced the sensitivity of PC72 transgenic (hsp16/lacZ) worms to cadmium, increasing expression of the reporter product, beta-galactosidase. The utility of this culture syst em for controlling oxygen availability during nematode growth and toxicity assays is discussed. (C) 1999 Elsevier Science Inc. All rights reserved.