Bacterial viability and oxidative stress
We observed that in E. coli, more than 95% of the total carbonyl content consisted of insoluble protein and most were cytosolic proteins. We thereby demonstrate that, in vivo, carbonylated proteins are detectable mainly in an aggregate state. Finally, we show that detectable carbonylated proteins are not degraded in vivo like it was previously proposed by Dukan et al., (2000). Here we propose that some carbonylated proteins escape degradation in vivo by forming carbonylated protein aggregates and thus becoming nondegradable. In light of these findings, we provide evidence that the accumulation of nondegradable carbonylated protein presented in an aggregate state contributes to the increases in carbonyl content observed in VBNC cells (Maisonneuve et al., 2008c).
Specific protein carbonylation of SN30, LP, and SP from an exponentially grown E. coli culture. Extracts from a French press CE of an exponentially grown culture of E. coli (OD600= 0.5) obtained after various centrifugation times were processed for resolution on 2D polyacrylamide. Autoradiograms were obtained after carbonyl immunoassay of proteins. Molecular masses (M) in kDa are indicated on the left.
Diagram shows the separation of the pellets and supernatant