Data from: Multicopy single-stranded DNA directs intestinal colonization of enteric pathogens

Multicopy single-stranded DNAs (msDNAs) are hybrid RNA-DNA molecules
encoded on retroelements called retrons and produced by the action of
retron reverse transcriptases. Retrons are widespread in bacteria but the
natural function of msDNA has remained elusive despite 30 years of study.
The major roadblock to elucidation of the function of these unique
molecules has been the lack of any identifiable phenotypes for mutants
unable to make msDNA. We report that msDNA of the zoonotic pathogen
Salmonella Typhimurium is necessary for colonization of the intestine.
Similarly, we observed a defect in intestinal persistence in an
enteropathogenic E. coli mutant lacking its retron reverse transcriptase.
Under anaerobic conditions in the absence of msDNA, proteins of central
anaerobic metabolism needed for Salmonella colonization of the intestine
are dysregulated. We show that the msDNA-deficient mutant can utilize
nitrate, but not other alternate electron acceptors in anaerobic
conditions. Consistent with the availability of nitrate in the inflamed
gut, a neutrophilic inflammatory response partially rescued the ability of
a mutant lacking msDNA to colonize the intestine. These findings together
indicate that the mechanistic basis of msDNA function during Salmonella
colonization of the intestine is proper production of proteins needed for
anaerobic metabolism. We further conclude that a natural function of msDNA
is to regulate protein abundance, the first attributable function for any
msDNA. Our data provide novel insight into the function of this mysterious
molecule that likely represents a new class of regulatory molecules.