Identification of Genes Contributing to the Virulence of Francisella tularensis SCHU S4 in a Mouse Intradermal Infection Model

Background: Francisella tularensis is a highly virulent human pathogen. The most virulent strains belong to subspecies tularensis and these strains cause a sometimes fatal disease. Despite an intense recent research effort, there is very limited information available that explains the unique features of subspecies tularensis strains that distinguish them from other F. tularensis strains and that explain their high virulence. Here we report the use of targeted mutagenesis to investigate the roles of various genes or pathways for the virulence of strain SCHU S4, the type strain of subspecies tularensis. Methodology/Principal Findings: The virulence of SCHU S4 mutants was assessed by following the outcome of infection after intradermal administration of graded doses of bacteria. By this route, the LD\u2085\u2080 of the SCHU S4 strain is one CFU. The virulence of 20 in-frame deletion mutants and 37 transposon mutants was assessed. A majority of the mutants did not show increased prolonged time to death, among them notably \u394pyrB and \u394recA. Of the remaining, mutations in six unique targets, tolC, rep, FTT0609, FTT1149c, ahpC, and hfq resulted in significantly prolonged time to death and mutations in nine targets, rplA, wbtI, iglB, iglD, purL, purF, ggt, kdtA, and glpX, led to marked attenuation with an LD\u2085\u2080 of >10\ub3 CFU. In fact, the latter seven mutants showed very marked attenuation with an LD\u2085\u2080 of 6510\u2077 CFU. Conclusions/Significance: The results demonstrate that the characterization of targeted mutants yielded important information about essential virulence determinants that will help to identify the so far little understood extreme virulence of F. tularensis subspecies tularensis.Peer reviewed: YesNRC publication: Ye

Kiri P. A. Hullin'ile

Lobau, Georges Mouton de, 1770-1838, prantsuse marssal, Napoleon I adjutantHullin, Pierre Augustin, 1758-1841, prantsuse väejuht Napoleoni armeesSõjaväeparaadi tsermoniaalküsimuse

Commission municipale de Paris. [Réglement pour les offrandes patriotiques. Signé : Lobau, Mauguin. 2 août 1830.]

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Structure of bovine mitochondrial F1-ATPase with nucleotide bound to all three catalytic sites: implications for the mechanism for rotary catalysis

AbstractThe crystal structure of a novel aluminium fluoride inhibited form of bovine mitochondrial F1-ATPase has been determined at 2 Å resolution. In contrast to all previously determined structures of the bovine enzyme, all three catalytic sites are occupied by nucleotide. The subunit that did not bind nucleotide in previous structures binds ADP and sulfate (mimicking phosphate), and adopts a “half-closed” conformation. This structure probably represents the posthydrolysis, pre-product release step on the catalytic pathway. A catalytic scheme for hydrolysis (and synthesis) at physiological rates and a mechanism for the ATP-driven rotation of the γ subunit are proposed based on the crystal structures of the bovine enzyme