Equivalence of AM1 strains during tests of long-term growth and survival. Co-cultures were created by mixing either Modern (black circles) or Archival AM1 (gray squares) with a fluorescently labeled Modern reference, and the change in unlabeled versus fluorescent cells was monitored over time using flow cytometry. A) In continually shaken flasks with succinate, the Archival strain increased in frequency over the first two days of growth and maintained this advantage over Modern over time. B) Similarly, Archival increased in frequency during four days of growth on methylamine agar plates (not shown), and maintained this frequency during long-term storage at 4°C. Values represent the mean plus SEM of the percent unlabeled cells measured in three replicate co-cultures.