Noel Christophe

No Thumbnail Available
Last Name
First Name

Search Results

Now showing 1 - 2 of 2
  • Preprint
    The presence of four iron-containing superoxide dismutase isozymes in Trypanosomatidae : characterization, subcellular localization, and phylogenetic origin in Trypanosoma brucei
    ( 2005-08-11) Dufernez, Fabienne ; Yernaux, Cedric ; Gerbod, Delphine ; Noel, Christophe ; Chauvenet, Melanie ; Wintjens, Rene ; Edgcomb, Virginia P. ; Capron, Monique ; Opperdoes, Fred R. ; Viscogliosi, Eric
    Metalloenzymes such as the superoxide dismutases (SODs) form part of a defense mechanism that helps protect obligate and facultative aerobic organisms from oxygen toxicity and damage. Here, we report the presence in the trypanosomatid genomes of four SOD genes: soda, sodb1 and sodb2 and a newly identified sodc. All four genes of Trypanosoma brucei have been cloned (Tbsods), sequenced and overexpressed in Escherichia coli and shown to encode active dimeric FeSOD isozymes. Homology modelling of the structures of all four enzymes using available X-ray crystal structures of homologs showed that the four TbSOD structures were nearly identical. Subcellular localization using GFP-fusion proteins in procyclic insect trypomastigotes shows that TbSODB1 is mainly cytosolic, with a minor glycosomal component, TbSODB2 is mainly glycosomal with some activity in the cytosol and TbSODA and TbSODC are both mitochondrial isozymes. Phylogenetic studies of all available trypanosomatid SODs and 106 dimeric FeSODs and closely related cambialistic dimeric SOD sequences suggest that the trypanosomatid SODs have all been acquired by more than one event of horizontal gene transfer, followed by events of gene duplication.
  • Article
    Molecular phylogenies of Blastocystis isolates from different hosts : implications for genetic diversity, identification of species, and zoonosis
    (American Society for Microbiology, 2005-01) Noel, Christophe ; Dufernez, Fabienne ; Gerbod, Delphine ; Edgcomb, Virginia P. ; Delgado-Viscogliosi, Pilar ; Ho, Lip-Chuen ; Singh, Mulkit ; Wintjens, Rene ; Sogin, Mitchell L. ; Capron, Monique ; Pierce, Raymond ; Zenner, Lionel ; Viscogliosi, Eric
    Small-subunit (SSU) rRNA gene sequences were obtained by PCR from 12 Blastocystis isolates from humans, rats, and reptiles for which elongation factor 1{alpha} (EF-1{alpha}) gene sequences are already available. These new sequences were analyzed by the Bayesian method in a broad phylogeny including, for the first time, all Blastocystis sequences available in the databases. Phylogenetic trees identified seven well-resolved groups plus several discrete lineages that could represent newly defined clades. Comparative analysis of SSU rRNA- and EF-1{alpha}-based trees obtained by maximum-likelihood methods from a restricted sampling (13 isolates) revealed overall agreement between the two phylogenies. In spite of their morphological similarity, sequence divergence among Blastocystis isolates reflected considerable genetic diversity that could be correlated with the existence of potentially ≥12 different species within the genus. Based on this analysis and previous PCR-based genotype classification data, six of these major groups might consist of Blastocystis isolates from both humans and other animal hosts, confirming the low host specificity of Blastocystis. Our results also strongly suggest the existence of numerous zoonotic isolates with frequent animal-to-human and human-to-animal transmissions and of a large potential reservoir in animals for infections in humans.