A small, microRNA-size, ribonucleic acid regulating gene expression and development of Shiga toxin-converting bacteriophage ▪24b

Abstract

A microRNA-size (20-nt long) molecule has been identified in Escherichia coli after induction of Shiga toxin-converting bacteriophage ▪24 B. This small RNA, named 24B1, is encoded in the lom-vb 24B 43 region of the phage genome, and apparently it is produced by cleavage of a larger transcript. A phage devoid of 24B1 revealed decreased efficiency of lysogenization, quicker prophage induction after provoking the SOS response, higher efficiency of progeny phage production during the lytic cycle and less efficient adsorption on the host cells. Expression of most of phage genes was drastically increased after infection of E. coli by the ▪24 B "24B1 phage. Since 24B1 may impair expression of the d ant gene, coding for an anti-repressor, these results may explain the mechanism of regulations of the physiological processes by this small RNA due to impaired activity of the cI repressor and changed expression of vast majority of phage genes. To our knowledge, this is the first example of functional microRNA-size molecule in bacterial cells.