Guterman S K, Luria S E
Science. 1969 Jun 20;164(3886):1414. doi: 10.1126/science.164.3886.1414.
Mutants exb of Escherichia coli are insensitive to colicin B and excrete into their culture media a material that inhibits colicin activity and that appears to be the bacterial lipopolysaccharide.