The researchers studied the effects of overproducing two molecular chaperones, DnaK and DnaJ, in E. coli bacteria. They found that overproducing DnaK destabilized plasmids, but co-overproducing DnaJ with DnaK stabilized plasmid levels. Moderate DnaK overproduction caused cell division defects, but adding DnaJ reversed this effect. High levels of DnaK stopped bacterial growth, and DnaK overproduction was found to be harmful to the bacteria, especially in stationary phase. The study shows that the balance between DnaK and DnaJ levels is crucial for bacterial survival and growth.