Bacterial Genome Containing Chimeric DNA–RNA Sequences

Almost five decades ago Crick, Orgel,
and others proposed the RNA
world hypothesis. Subsequent studies have raised the possibility that
RNA might be able to support both genotype and phenotype, and the
function of RNA templates has been studied in terms of evolution,
replication, and catalysis. Recently, we engineered strains of E. coli in which a large fraction of 2′-deoxycytidine
in the genome is substituted with the modified base 5-hydroxymethyl-2′-deoxycytidine.
We now report the generation of mutant strains derived from these
engineered bacteria that show significant (∼40–50%)
ribonucleotide content in their genome. We have begun to characterize
the properties of these chimeric genomes and the corresponding strains
to determine the circumstances under which E. coli can incorporate ribonucleotides into its genome and herein report
our initial observations.