The disulfide bond formation pathway is essential for anaerobic growth of Escherichia coli

Abstract

Disulfide bonds are critical to the stability and function of many bacterial proteins. In the periplasm of Escherichia coli, intramolecular disulfide bond formation is catalyzed by the two-component disulfide bond forming (DSB) system. Inactivation of the DSB pathway has been shown to lead to a number of pleotropic effects, although cells remain viable under standard laboratory conditions. However, we show here that dsb strains of E. coli reversibly filament under aerobic conditions and fail to grow anaerobically unless a strong oxidant is provided in the growth medium. These findings demonstrate that the background disulfide bond formation necessary to maintain the viability of dsb strains is oxygen dependent. LptD, a key component of the lipopolysaccharide transport system, fails to fold properly in dsb strains exposed to anaerobic conditions, suggesting that these mutants may have defects in outer membrane assembly. We also show that anaerobic growth of dsb mutants can be restored by suppressor mutations in the disulfide bond isomerization system. Overall, our results underscore the importance of proper disulfide bond formation to pathways critical to E. coli viability under conditions where oxygen is limited.