Pacocha Sarah E.

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Pacocha
First Name
Sarah E.
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  • Article
    In vitro generation of human high-density-lipoprotein-resistant Trypanosoma brucei brucei
    (American Society for Microbiology, 2006-08) Faulkner, Sara D. ; Oli, Monika W. ; Kieft, Rudo ; Cotlin, Laura F. ; Widener, Justin ; Shiflett, April M. ; Cipriano, Michael J. ; Pacocha, Sarah E. ; Birkeland, Shanda R. ; Hajduk, Stephen L. ; McArthur, Andrew G.
    The host range of African trypanosomes is influenced by innate protective molecules in the blood of primates. A subfraction of human high-density lipoprotein (HDL) containing apolipoprotein A-I, apolipoprotein L-I, and haptoglobin-related protein is toxic to Trypanosoma brucei brucei but not the human sleeping sickness parasite Trypanosoma brucei rhodesiense. It is thought that T. b. rhodesiense evolved from a T. b. brucei-like ancestor and expresses a defense protein that ablates the antitrypanosomal activity of human HDL. To directly investigate this possibility, we developed an in vitro selection to generate human HDL-resistant T. b. brucei. Here we show that conversion of T. b. brucei from human HDL sensitive to resistant correlates with changes in the expression of the variant surface glycoprotein (VSG) and abolished uptake of the cytotoxic human HDLs. Complete transcriptome analysis of the HDL-susceptible and -resistant trypanosomes confirmed that VSG switching had occurred but failed to reveal the expression of other genes specifically associated with human HDL resistance, including the serum resistance-associated gene (SRA) of T. b. rhodesiense. In addition, we found that while the original active expression site was still utilized, expression of three expression site-associated genes (ESAG) was altered in the HDL-resistant trypanosomes. These findings demonstrate that resistance to human HDLs can be acquired by T. b. brucei.
  • Preprint
    Genotypic diversity within a natural coastal bacterioplankton population
    ( 2005-01-04) Thompson, Janelle R. ; Pacocha, Sarah E. ; Pharino, Chanathip ; Klepac-Ceraj, Vanja ; Hunt, Dana E. ; Benoit, Jennifer ; Sarma-Rupavtarm, Ramahi ; Distel, Daniel L. ; Polz, Martin F.
    The genomic diversity and relative importance of unique genotypes within natural bacterial populations has remained largely unknown. Here, we analyze the diversity and annual dynamics of a group of coastal bacterioplankton (>99% 16S rRNA identity to Vibrio splendidus). We show that this group consists of at least a thousand distinct genotypes, each occurring at extremely low environmental concentrations (on average <1 cell/ml). Overall, the genomes show extensive allelic diversity and size variation. Individual genotypes rarely recurred in samples and allelic distribution did not show spatial or temporal substructure. Ecological considerations suggest that much genotypic and possibly phenotypic variation within natural populations should be considered neutral.