Sarah ReillyJunior MICRO major One of the most up and coming topics in the biology world right now is “what is in the gut microbiome and how much does it impact your health?” Last December, I applied for the Mentor/Mentee Howard Hughes Medical Institute Research Fellowship to do research over summer 2019. This was a matching program that was run by Dr. Nancy Kaufmann where students applied and interviewed to find a lab of interest in the Department of Biological Sciences. One of the unique parts of this program was that in addition to matching you with an interesting research lab, they also matched you with an undergraduate research mentor - a student who had been doing research in the department for a while. Unfortunately, summer 2019 was the last year for this program, but there are lots of other summer research programs out there (see: https://www.biology.pitt.edu/undergraduate/research/outside-pitt and https://www.biology.pitt.edu/undergraduate/awards-and-fellowships). I knew I wanted to do research as soon as I came to Pitt. I was very interested in the gut microbiota because my grandfather was diagnosed with a Clostridium difficile infection and the impact it had on him was something I have never seen before because doctors cannot do much about it. Words like “probiotics” and “immunity” are thrown around a lot when referring to this topic because eating living microbes such a yogurt, kombucha and kimchi are supposedly good for your health. After going through the interview, I was matched with Dr Kevin Kohl’s lab where he studies the physiological ecology and microbial ecology of the digestive system and gut microbiota of many vertebrate species such as birds, amphibians, fish, and mammals. To start the summer, Sarah H. (a Bio Peer Advisor who was also matched into the Kohl Lab) and I began immediately grinding fecal samples from different rodents. These samples ended up being the focus on our project for the summer. We continuously worked on a cellulase assay for different fecal samples in woodrats, Montane voles and grasshopper mice but we also focused on fiber digestibility; which is what my poster was focused on. It’s important to note that these rodents represent various feeding habits. The woodrat is an omnivore, the Montane vole is a herbivore and the grasshopper mouse is an insectivore. All rodents have an organ known as a cecum which is where certain bacteria is held to break down the cellulose in the fiber to create sugar and energy for the animal. These rodents were all fed four different diets with different percentages of fiber and protein with carbohydrates and fat as “fillers” to hold ecological relevance to the diet of the animal. Feeding the rodents and collecting their feces (that they naturally excreted) took place in summer 2018 and the feces was kept in 15ml conical tubes until ready for use. The main goal of my research over the 2019 summer was looking to find any correlations between the cecum size and fiber digestibility in Montane voles. It is assumed that the Montane vole should have a lot of fiber digestibility because it is a herbivore, thus meaning that it would have to break down more fiber due to the content in plants. The hypothesis is that voles with larger cecum sizes should be able to digest more fiber because they would have more bacteria to initiate fiber digestion. The neutral detergent fiber analysis and acid detergent fiber analysis processes to measure fiber digestibility was something that neither Sarah H. nor myself had seen before. The feces that was ground up is placed into little bags that very much resemble tea bags (that would be very bad to mix those up!) and are heat- sealed to ensure that no sample is lost. All of these samples were weighed and kept on record to use after the analysis. These bags are then tiered on top of one another into a ANKOM Fiber Analyzer Vessel where boiling water mixed with neutral fiber detergent and amylase is poured over top of them. The neutral detergent breaks down pectins, proteins, and minerals to leave everything else that may have been in the feces behind and the amylase breaks down starch and glycogen. These bags are then heated and agitated and then soaked in acetone to dehydrate them. These bags are then kept under the fume hood overnight to dry and placed in an oven to continue drying. Once the bags are done drying, their weight is recorded, and the process is repeated but acid detergent solution is used. The acid detergent solution dissolves remaining cell solubles, lignin and some hemicellulose. After the bags are dried once more, they are weighed, and only fiber content remained. All parts of the Montane vole were measured and weighed during dissection by the post-doc in our lab, Brian Trevelline. After some calculations, we determined that cecum size and fiber digestibility are correlated. This summer research fellowship led to a position working in the lab over the semester for credit where Sarah and I will focus on experimental evolution with cellulase activity in specific microbes from the woodrat gut biome. By doing projects like these in the Kohl lab, we can determine which microbes play certain roles in the gut microbiome to lead to more advances in studying what their specific functions are! Stay tuned to hear more about how Sarah R. and other Bio Peer Advisors got involved in research. Here is a sneak peek:
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