Retron reverse transcriptase rrtT is ubiquitous in strains of Salmonella enterica serovar Typhimurium

Bacterial retron reverse transcriptases are unusual enzymes which utilise the same RNA molecule as a template and also as a primer for initiation of the reverse transcription. Except for their relatively frequent presence in Myxococcus spp., they are considered as quite rare proteins. However, in this study we proved that retron reverse transcriptase is frequently found in certain serovars of Salmonella enterica. Using polymerase chain reaction (PCR), in strains of serovar Typhimurium, the rrtT (retron reverse transcriptase Typhimurium) gene was detected in 158 out of 175 tested field strains. On the other hand, in none of the 18 tested serovar Enteritidis strains the rrtT was detected in their genome. Detailed computer analysis allowed us to predict the sequence of msDNA and to propose that the final msDNA is free of any RNA. Furthermore, we predict that there are at least three different classes of retron reverse transcriptases.