The role of an encapsulin nanocompartment in resisting silver ion stress

Abstract

Background: Compartmentalization can protect cells from the interference of external toxic substances by sequestering toxic products. We hypothesized that proteinaceous nanocompartments may be a feasible candidate material to be added to genetically modified bacteria for the sequestration of toxic environmental products, which would open up a new biological detoxification pathway. Results: Here, we identified a new mechanism by which bacteria resist silver ion stress. We showed that the self-assembling nanocompartments helped a model species ( E. coli ) resist silver ion stress. Transmission electron microscopy and energy dispersive X-ray (TEM-EDX) analysis showed that the nanocompartments combined stably with silver ions in vitro . In addition, when exposed to 30 μM AgNO 3 , the survival rate of genetically modified bacteria (with nanocompartments) was 86%, while it was just 59% in the wild-type bacteria (without nanocompartments). Label-free quantitative proteomics indicated that the nanocompartments enhanced bacterial activity by inducing the up-regulation of protein processing and secondary metabolites, and decreased their intracellular silver ion concentration, both of which contributed to their increased resistance to toxic silver ions. Conclusions: This study on nanocompartments has contributed to a deeper understanding of how bacteria respond to environmental stressors like heavy metal pollutants in water, soil, and sediment. The encapsulin nanocompartment has the potential to be applied in various environments.