Once every couple of years we grow a large (12 l. ?) fermenter of HB101, collect about 5 kilos of bacteria, resupend it 1:1 in M9, freeze it at -80, and use it to feed liquid worm cutures (that also contain pen/step). It is a smelly job, but covenient and the worms grow very well in dense cutures. OP50 should also work, but it does not grow as well. Nick Rhind