ABSTRACTDespite recent advances in our understanding of howHelicobacter pyloricauses disease, the factors that allow this pathogen to persist in the stomach have not yet been fully characterized. To identify new virulence factors inH. pylori, we generated low-infectivity variants of a mouse-colonizingH. pyloristrain using the classical technique ofin vitroattenuation. The resulting variants and their highly infectious progenitor bacteria were then analyzed by global gene expression profiling. The gene expression levels of five open reading frames (ORFs) were significantly reduced in low-infectivity variants, with the most significant changes observed for ORFs HP1583 and HP1582. These ORFs were annotated as encoding homologs of theEscherichia colivitamin B6biosynthesis enzymes PdxA and PdxJ. Functional complementation studies withE. coliconfirmedH. pyloriPdxA and PdxJ to bebona fidehomologs of vitamin B6biosynthesis enzymes. Importantly,H. pyloriPdxA was required for optimal growthin vitroand was shown to be essential for chronic colonization in mice. In addition to having a well-known metabolic role, vitamin B6is necessary for the synthesis of glycosylated flagella and for flagellum-based motility inH. pylori. Thus, for the first time, we identify vitamin B6biosynthesis enzymes as novel virulence factors in bacteria. Interestingly,pdxAandpdxJorthologs are present in a number of human pathogens, but not in mammalian cells. We therefore propose that PdxA/J enzymes may represent ideal candidates for therapeutic targets against bacterial pathogens.IMPORTANCEApproximately half of the world’s population is infected withH. pylori, yet howH. pyloribacteria establish chronic infections in human hosts remains elusive. From gene array studies, we identified two genes as representing potentially novel colonization factors forH. pylori. These genes encoded enzymes involved in the synthesis of vitamin B6, an important molecule for many metabolic reactions in living organisms. Little is currently known regarding vitamin B6biosynthesis in human pathogens. We showed that mutantH. pyloribacteria lacking an enzyme involved inde novovitamin B6biosynthesis, PdxA, were unable to synthesize motility appendages (flagella) and were unable to establish chronic colonization in mice. Thus, this work identifies vitamin B6biosynthesis enzymes as novel virulence factors for bacterial pathogens. Interestingly, a number of human pathogens, but not their mammalian hosts, possess these genes, which suggests that Pdx enzymes may represent ideal candidates for new therapeutic targets.
Metal homeostasis in pathogenic Epsilonproteobacteria: Mechanisms of acquisition and regulation
