Nematode growth medium A defined chemical medium which has proven to be adequate to produce a healthy culture of C. elegans when seeded with an E. coli OP50 lawn of bacteria and is typically poured into petri plates using a peristaltic pump. To reduce the grown of unwanted bacteria and fungi, drugs such as streptomycin or nystatin can be added to the solution before being poured ( Stiernagle, 2006).