Membrane-derived oligosaccharides (MDOs) are essential for sodium dodecyl sulfate resistance in Escherichia coli

We studied the role of membrane-derived oligosaccharides (MDOs) in sodium dodecyl sulfate (SDS) resistance by Escherichia coli. MDOs are also known as osmoregulated periplasmic glucans. Wild-type E. coli MC4100 grew in the presence of 10% SDS whereas isogenic mdoA and mdoB mutants could not grow above 0.5% SDS. Similarly, E. coli DF214, a mutant (pgi, zwf) unable to grow on glucose, exhibited conditional sensitivity to SDS in that it grew in gluconate and glucose or galactose but not in gluconate and mannose or sorbose. DF214 requires both gluconate and glucose/galactose because the gluconate is used for energy production, while glucose/galactose is used for MDO synthesis. Finally, the fate of E. coli cells subjected to SDS shock either during growth or when used as an inoculum is dependent on the presence or absence of sufficient MDOs. In both cases, cells grown under high-osmolarity (low-MDO) conditions were rapidly lysed by 5% SDS. Based on findings from a wild-type E. coli (MC4100), two mdo mutants and strain DF214 we conclude that MDOs are required for SDS resistance.