Persistence preserves phenotypic heterogeneity in non-genetic formaldehyde resistance in Escherichia coli

Recently, it was discovered that Methylobacterium extorquens possesses a spectrum of phenotypic states conferring non-genetic resistance to formaldehyde. The non-genetic resistance allowed rapid growth on levels of formaldehyde which were lethal to the majority of the population. To investigate whether this is a common phenomenon, we tested the distantly related Escherichia coli for heterogeneity to formaldehyde stress during growth on glucose. Like M. extorquens, E. coli populations have a wide, reversible, continuous range of non-genetic resistance to formaldehyde. However, there were differences from what was found for M. extorquens. Most E. coli growth occurred after formaldehyde levels had dropped, suggesting that an effect similar to antibiotic persistence could be the cause. We found the dormant cell state can maintain formaldehyde resistance through the lack of dilution of the proteome caused by growth. These data suggest that dormancy can preserve phenotypic heterogeneities in other traits.