Caenorhabditis briggsae: Electron microscope analysis of changes in negative surface charge density of the outer cuticular membrane

Abstract

The negative surface charge density of the outer cuticular membrane of Caenorhabditis briggsae was visualized by use of cationized ferritin. When grown axenically in a medium which contained liver extract, the net negative surface charge density was significantly less in nematodes 21–24 days old than in nematodes 6–7 days old. Nematodes grown in heattreated medium, in which liver enzyme activities were presumably inactivated, did not show lower surface charge densities at 21 days. These findings indicate that the decrease in net negative surface charge was caused by a receptor-destroying enzyme present in the liver extract. The relation of the membrane charge changes observed in vitro to those which might occur in nature is discussed. Further studies showed that the negative charges are evenly distributed over the surface of the nematode except in the tail area, where they are lower.