Published online by Cambridge University Press: 06 April 2009
1. Cysts, formed in a strain of E. invadens growing with a mixed bacterial flora, were sterilized of all but one species of bacterium (organism x), by treatment with chemicals. Strains of E. invadens derived from these cysts were prepared, growing with organism x and either Bact. coli or B. megatherium.
2. A monobacterial strain of E. invadens, growing with Bact. coli alone, was obtained by maintaining a dibacterial strain, growing with organism x and Bact. coli, for 72 days in medium containing gentian violet.
3. A monobacterial strain of E. invadens, growing with Staph. albus, was prepared from cysts, produced in the monobacterial strain of E. invadens + Bact. coli, and sterilized by treatment with chemicals.
4. An axenic strain of E. invadens was prepared by maintaining the monobacterial strain of E. invadens + Staph. albus, in saline-liver medium containing antibiotics. This axenic strain has now been maintained for over 14 months in saline containing untreated, sterile liver, but no antibiotics.