Effects of aminoglycosides and spectinomycin on the synthesis and release of lipopolysaccharide by Escherichia coli.

The effects of aminoglycosides and spectinomycin on lipopolysaccharide (LPS) synthesis and release by Escherichia coli were studied. LPS synthesis was previously reported to be regulated by the stringent control mechanism. In agreement with this, the control of LPS synthesis in amino acid-deprived relA+ cells was relaxed by spectinomycin, a proven stringent control antagonist, but not by kanamycin, an agent which is ineffective as a stringent control antagonist. The other stringent control antagonists tested (gentamicin, tobramycin, and, to a lesser extent, amikacin) unexpectedly failed to relax the control of LPS synthesis, and this was subsequently shown to be due to their inhibitory action on LPS synthesis. The release of LPS by nongrowing (amino acid-deprived and antibiotic-treated) bacteria was stimulated only under conditions in which the control of LPS synthesis was relaxed.