Escherichia coli mutant Y16 is a double mutant carrying thermosensitive ftsH and ftsI mutations.

The Escherichia coli mutant Y16, which shows thermosensitive colony formation and filamentation with reduced amounts of penicillin-binding protein 3 (PBP3), has mutations in the ftsI gene encoding PBP3 and in the ftsH gene. The ftsI mutation markedly reduces the amount of PBP3 at 42 degrees C, whereas the amount of the ftsH single mutant is slightly reduced.