Bioassay used to detect cobamides in extracts. Cbl-dependent growth of serovar Typhimurium was assessed in minimal medium supplemented with glycerol, DMB, and HPLC-purified corrinoids. NorCbl and UNK2 are cobamides purified from cells grown on minimal medium supplemented with Cby, DMB, and EA-P. UNK1 identifies a cobamide purified from cells grown in medium supplemented with Cby, DMB, and l-Thr-P. The numbers between parentheses show retention times on RP HPLC analysis. The indicator strain used in these studies was strain JE8214 (cobS1312::cat+), a cobamide auxotroph.