The Sole DEAD-Box RNA Helicase of the Gastric Pathogen Is Essential for Colonization.

Present in every kingdom of life, generally in multiple copies, DEAD-box RNA helicases are specialized enzymes that unwind RNA secondary structures. They play major roles in mRNA decay, ribosome biogenesis, and adaptation to cold temperatures. Most bacteria have multiple DEAD-box helicases that present both specialized and partially redundant functions. By using phylogenomics, we revealed that the genus, including the major gastric pathogen , is among the exceptions, as it encodes a sole DEAD-box RNA helicase. In , this helicase, designated RhpA, forms a minimal RNA degradosome together with the essential RNase, RNase J, a major player in the control of RNA decay. Here, we used as a model organism with a sole DEAD-box helicase and investigated the role of this helicase in physiology, ribosome assembly, and during colonization. Our data showed that RhpA is dispensable for growth at 37°C but crucial at 33°C, suggesting an essential role of the helicase in cold adaptation. Moreover, we found that a Δ mutant was impaired in motility and deficient in colonization of the mouse model. RhpA is involved in the maturation of 16S rRNA at 37°C and is associated with translating ribosomes. At 33°C, RhpA is, in addition, recruited to individual ribosomal subunits. Finally, via its role in the RNA degradosome, RhpA directs the regulation of the expression of its partner, RNase J. RhpA is thus a multifunctional enzyme that, in , plays a central role in gene regulation and in the control of virulence. We present the results of our study on the role of RhpA, the sole DEAD-box RNA helicase encoded by the major gastric pathogen We observed that all the species possess such a sole helicase, in contrast to most free-living bacteria. RhpA is not essential for growth of under normal conditions. However, deletion of leads to a motility defect and to total inhibition of the ability of to colonize a mouse model. We also demonstrated that this helicase encompasses most of the functions of its specialized orthologs described so far. We found that RhpA is a key element of the bacterial adaptation to colder temperatures and plays a minor role in ribosome biogenesis. Finally, RhpA regulates transcription of the gene encoding RNase J, its essential partner in the minimal RNA degradosome, and thus plays a crucial role in the control of RNA decay.