title: Characterization of a novel Neisseria meningitidis Fur and iron-regulated operon required for protection from oxidative stress: utility of DNA microarray in the assignment of the biological role of hypothetical genes.
abstract: We have previously shown that in the human pathogen Neisseria meningitidis group B (MenB) more than 200 genes are regulated in response to growth with iron. Among the Fur-dependent, upregulated genes identified by microarray analysis was a putative operon constituted by three genes, annotated as NMB1436, NMB1437 and NMB1438 and encoding proteins with so far unknown function. The operon was remarkably upregulated in the presence of iron and, on the basis of gel retardation analysis, its regulation was Fur dependent. In this study, we have further characterized the role of iron and Fur in the regulation of the NMB1436-38 operon and we have mapped the promoter and the Fur binding site. We also demonstrate by mutant analysis that the NMB1436-38 operon is required for protection of MenB to hydrogen peroxide-mediated killing. By using both microarray analysis and S1 mapping, we demonstrate that the operon is not regulated by oxidative stress signals. We also show that the deletion of the NMB1436-38 operon results in an impaired capacity of MenB to survive in the blood of mice using an adult mouse model of MenB infection. Finally, we show that the NMB1436-38 deletion mutant exhibits increased susceptibility to the killing activity of polymorphonuclears (PMNs), suggesting that the 'attenuated' phenotype is mediated in part by the increased sensitivity to reactive oxygen species-producing cells. This study represents one of the first examples of the use of DNA microarray to assign a biological role to hypothetical genes in bacteria.
authors.affiliation: Chiron Vaccines, Via Fiorentina 1, 53100 Siena, Italy.
authors.forename: Renata
authors.initials: R
authors.lastname: Grifantini
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Frigimelica
authors.forename: Isabel
authors.initials: I
authors.lastname: Delany
authors.forename: Erika
authors.initials: E
authors.lastname: Bartolini
authors.forename: Serena
authors.initials: S
authors.lastname: Giovinazzi
authors.forename: Sergio
authors.initials: S
authors.lastname: Balloni
authors.forename: Sarika
authors.initials: S
authors.lastname: Agarwal
authors.forename: Giuliano
authors.initials: G
authors.lastname: Galli
authors.forename: Caroline
authors.initials: C
authors.lastname: Genco
authors.forename: Guido
authors.initials: G
authors.lastname: Grandi
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D008589:Meningococcal Infections; D051379:Mice; D008807:Mice, Inbred BALB C; D009345:Neisseria meningitidis / Q000235:genetics* / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D009876:Operon; D016877:Oxidants / Q000378:metabolism; D018384:Oxidative Stress; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015996:Survival Rate
chemical_list: D001426:Bacterial Proteins; D016877:Oxidants; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D006861:Hydrogen Peroxide; D007501:Iron