Key features and details: Bulk powder, easily weighed to make custom batch sizes. LB Agar Medium is a nutritionally rich medium originally developed for growth and maintenance of E. coli strains. LB Agar Medium supports a luxurious growth of E. coli cells as tryptone and yeast extract supply essential growth factors that E. coli cells would otherwise have to synthesize. The medium also contains essential electrolytes for transport and osmotic balance, due to the NaCl component.