Username Week 7

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Theresa Graebener

Week 7 Assignment

10 Words I Did Not Know

  1. Hyperinfectious- hyperinfection- infection by very large numbers of organisms as a result of immunologic deficiency
  2. Serological- serology- the science dealing with the immunological properties and actions of serum
  3. Murine- belonging or pertaining to the Muridae, the family of rodents that includes mice and rats
  4. Transiently- not lasting, enduring, or permanent; transitory.
  5. Indices- plural of index
  6. Canonical- pertaining to, established by, or conforming to a canon or canons.
  7. Quadruplicate- one of four copies or identical items, esp. copies of typewritten material.
  8. Elucidated- to provide clarification; explain.
  9. Chemotactic- oriented movement toward or away from a chemical stimulus.
  10. Dendrogram- a treelike diagram depicting evolutionary changes from ancestral to descendant forms, based on shared characteristics.
  11. Homogenized- to form by blending unlike elements; make homogeneous.

Outline: Host-induced epidemic spread of the cholera bacterium

Main Result:

  • Human colonization creates hyperinfectious bacteria
    • Maintained after dissemination
    • Contributes to spread of cholera
  • Transcriptional profiling of Vibiro cholerae from stool samples
    • Unique physiological and behavioral state
    • High expression levels of genes required for nutrient uptake and motility
    • Low expression levels of genes needed for chemotaxis

Importance:

  • Identified process by which cholera epidemics spread by human host
  • Provide insight into gene expression patterns of microorganisms
  • Human hosts provide suitable environment for growth

Limitations:

  • This experiment was brought about to: define the factors that enhance the transmission of pathogens during an epidemic
  • Previous experiments showed that LacZ plays significant role in bacterial growth

Methods:

  • Patients admitted to International Centre for Diarrhoeal Disease Research (ICDDR), Bangladesh, had stools pre-screened to verify presence of V. cholerae
    • Fresh samples collected, filtered, and frozen for RNA preparation
  • Competition assays made by mixing DSM-V984 with stool bacteria (1:10 ratio)
    • 50 microliters issued to 5-day-old Swiss Webster mice
    • Mice euthanized after 20-24 hours
    • Small intestines removed, homogenized, and plated to grow LacZ+ and LacZ- colonies
  • Competitions made with water incubated stool derived bacteria
    • Diluted into pond water and incubated at room temperature for 5 hours before mixing with DSM-V984 and inoculation into mice

Figures and Tables:

FIGURE 1 (competition assays)

  • Freshly isolated stool samples from six patients are on two competition assays.
    • On A the samples were mixed directly with in-vitro grown DSM-V984 and on B the samples were incubated in local pond water for 5 hours before mixing.
    • The Data points represent the output ratio of stool-derived V. cholerae to in-vitro grown competitor strain after correction for deviations in input rations.
      • Each data point represents the output from a single animal.
    • The geometric mean is indicated by a horizontal bar.
    • (n) is total number of animals per experiment

FIGURE 2 (transcription profile)

  • The cluster diagram shows the whole-genome expression profile of V. cholerae recovered from the stools of three ICDDR patients
  • Patients labeled A B or C, and replicate arrays are numbered 1-4
    • Dendogram shows tight clustering of technical replicates
    • Right panel is cluster diagram showing consistent differential regulation from patients A B and C
    • Fold changed relative to V. cholerae grown in vitro calculated using the avg values from the quadruplicate arrays on left
  • Red indicated a minimum twofold inc. in expression
  • Green represents a minimum twofold reduction in expression
  • Representative genes listed and their relative location indicated by arrow

How do Results Compare?

This paper did not compare its findings with any other bodies of work, however the authors did mention that their findings could lead to more research in the following areas:

  • Clarification of factor VCA0934.5 needed
    • Discovery emphasizes importance of analysis of DNA sequences that lie outside of the commonly annotated genes
  • Are other epidemic pathogens spread in a way that the agent is more infectious before or during its primary host?
  • Provide new targets for antimicrobial therapy to disable transmission
    • Eventually develop vaccine to prevent infection
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