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Enhanced survival of E. coli O157:H7
in Tetrahymena vesicles
By: Tyler Pannell, Undergraduate Student (Botany Concentration), Dept.
of Biology, Tennessee Technological University, Cookeville, TN 38505
Project Summary
• Problem: Do E. coli O157:H7 contained within
Tetrahymena vesicles live longer than free floating E.
coli?
• My objective is to show that E. coli O157:H7 survive
longer in ciliate vesicles than do E. coli that are freefloating in the environment.
• I will accomplish this goal by feeding Tetrahymena
ciliates E. coli O157:H7 and then observing the
percentage survival approximately every other day.
• I expect to see enhanced survival of E. coli O157:H7 in
vesicles as compared to the free-floating E. coli.
Introduction
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According to Rangel et. al. 8598 cases of E. coli O157:H7 were reported to
the CDC between 1982 and 2002.
The research of Johnston et. al. indicates that E. coli contamination in
produce increases during the packaging and processing of cantaloupe, but
not in green leafy vegetables.
Mubiru et. al. compared the survival rates of pathogenic versus
nonpathogenic E. coli and discovered that there is no statistical difference in
mortality between the two groups of E. coli grown under different physical
and chemical soil environments.
According to LeClerc et. al. antibacterial resistant pathogenic E. coli has a
high percentage of mutator phenotypes as a result of defective methyldirected mismatch repair gene sequences. This makes E. coli O157
hypermutable (i.e capable of surviving under a wider array of environmental
conditions/disruptions).
According to Gortz new methods for detecting intracellular bacteria have
emerged and will likely lead to greater awareness of the diversity of
intracellular bacterial symbionts – this awareness will help better predict
how protozoa and symbiont bacteria will interact.
Literature Cited
• Gortz, Hanz-Dieter. 2001. Intracellular bacteria in ciliates.
International Microbiology 4: 143-150.
• Johnston, L. M., L. Jaykus, D. Moll, M. C. Martinez, J. Anciso, B.
Mora, C. L. Moe. 2005. A field study of the microbiological quality of
fresh produce. Journal of Food Protection 68: 1840-1847.
• Leclerc, J. E., B. Li, W. L. Payne, T. A. Cebula. 1996. High mutation
frequencies among Escherichia coli and Salmonella pathogens.
Science 274: 1208-1211.
• Mubiru, D. N., M. S. Coyne, J. H. Grove. 2000. Mortality of
Escherichia coli O157:H7 in two soils with different physical and
chemical properties. Journal of Environmental Quality 29: 18211825.
• Rangel, J. M., P. H. Sparling, C. Crowe, P. M. Griffin, D. L.
Swerdlow. 2005. Epidemiology of Eschericia coli O157:H7
outbreaks, United States, 1982-2002. Emerging Infectious Diseases
11: 603-609.
Objective
• Because of the enhanced protection
afforded by the vesicles, E. coli O157:H7
will survive longer inside them than freefloating within the environment.
• Null Hypothesis: There will be no
difference in survival rates between freefloating E. coli O157:H7 and E. coli that
are enclosed in vesicles.
Methods and Materials
• Methods
– First, I will feed Tetrahymena with E. coli O157:H7. After waiting
for vesicle formation (~24 hrs), I will then use BacLite® to
determine the percenatage of live and dead bacteria inside
vesicles and free floating in the environment. Live E. coli will
fluoresce green and dead E. coli will fluoresce red.
– I will count the bacteria inside the vesicles and (if free-floating)
inside a grid on the microscope ~ every other day and use the
Hypothesis Test to determine whether there is a significant
difference between the bacteria growing inside vesicles
compared to those free-floating in the environment. I will create
graphs to more clearly illustrate my results.
• Data Form 1
• Data Form 2
Expected Results and Benefits
• I expect that my research will provide
evidence that E. coli survives longer in
vesicles than free-floating in the
environment.
• Hopefully this will show that when bacteria
grow on produce (such as spinach) in
concert with protozoa, they pose a greater
health risk to humans than they would in
the absence of protozoa.
Project timeline
• Link
Budget
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