7-O-Demethylcelesticetin is an antibacterial agent produced by Streptomyces caelestis strain 22227a, a mutant of S. caelestis. This antibiotic was found to be as active as celesticetin in vitro. Treatment of 7-O-demethylcelesticetin with base yielded 7-O-demethyldesalicetin which also has antibacterial properties. Hydrazinolysis of 7-O-demethylcelesticetin gave 2'-hydroxyethyl thiolincosaminide, indicating that S. caelestis strain 22227a produces lincosamine, the aminosugar present in the lincosaminide antibiotics.