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Journal of Undergraduate Research

Keywords

gut microbiota, cancer metastasis in model organism, abnormal genetic line, D. melanogaster

College

Life Sciences

Department

Plant and Wildlife Sciences

Abstract

As early as the beginning of the 20th century, Metchnikoff proposed that putrefactive bacteria living in the digestive tracts of hosts contribute to various disease processes and that modification of microbiota composition through consumption of viable microbes might help to improve health and longevity. This theory of longevity was the basis for the relatively recent trend of probiotic foods, the idea being that “healthy” bacteria could be ingested to produce a positive phenotypic result. The probiotic approach to treatment has been limited to large processes such as digestion or correcting large deficiencies in humans, but as evidence continues to mount that microbes found in the gut of living animals influence host biology, gut microbes have been more intensively examined for their influence on specific host problems1,2,3. The living conditions of the model organism D. melanogaster, more commonly known as the fruit fly, can be manipulated such that flies develop and live in a completely sterile environment. Because a host organism develops its own unique gut micro population from its surroundings, fruit flies raised in these conditions will be devoid of any gut bacteria. Their environments can also be manipulated such that only one specific microflora population is introduced, allowing the establishment of a definitive results from certain gut microbes. Such experiments have helped show that certain bacteria have been proven to be directly involved in inflammation, development of colonic neoplasia, and immune responses to disease and cancer1. Specifically, in human patients, gut microbiota was found to play a role in the metastasis of tumors2. Because of the unique ability for fruit flies to be raised in completely sterile conditions or conditions with one specific bacteria, an experiment was designed to define what exact molecular action is responsible for improving a host’s response to cancer metastasis. Because of short lifespans, the cancer incidence rate with wild flies is almost zero. Pagliarini and Xu found that expression of the oncogenic RasV12 gene and inactivation of the scrib gene responsible for maintaining cell polarity would result in uncontrolled cancer growth3. Additionally, the RasV12 gene must be labeled with green fluorescent protein (GFP) so that metastatic events can be visualized. By establishing fruit fly lines carrying both mutations, we would have suitable organism to elucidate how gut microbes influence a host’s response to cancer. Our first responsibility is ensuring that two stock lines can be crossed to consistently produce offspring with both needed genetic mutations.

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