Marisy Nieto, Masters in Environmental Biology, 2026, Ft. Lauderdale, FL
At PennVet’s New Bolton Center campus, the Agricultural Systems and Microbial Genomics (ASMG) Laboratory is brewing up bacterial blends that could be used to help reduce methane emissions and improve cow health. I spent the summer working at the ASMG lab learning about the ways these particular bacteria interact with the digestive system of Holsteins (your typical black and white cow) and getting a first hand experience on what the U.S dairy industry is like.
I focused on investigating whether these probiotic bacteria performed equally well in other breeds—specifically, Jerseys, which are the second most popular dairy breed in the United States. While Holsteins and Jerseys may serve similar roles in milk production, their physiological and metabolic profiles differ, and we wanted to know how the differences extend to how their gut microbiomes respond to probiotics. We planned and carried out in-vitro two experiments with fecal samples from both Holstein and Jersey calves. Using various machines in the lab such as gas chromatography to measure gases as well as the HPLC (High Performance Liquid Chromatography) machine to get volatile fatty acids (VFAs) we would be able to see if the bacteria retained their effectiveness.
My days were split between fieldwork at local dairy farms and the lab. On the animal side, I got to see and assist with tasks like collecting fecal samples from calves for my project and watching cows get tubed and swabbed. At the lab I spent time going through a variety of microbiological research techniques such as extracting DNA/RNA from fecal samples, DNA barcoding, and analyzing the gas data from our invitros. I really enjoyed being able to get hands-on work and learning about the way dairy production and microbiology intersect.
Moreover, while at the lab, I was also able to engage with and help my labmates with their own projects, each of which was exploring something different that would be used to further understand the cow’s microbiome. I was constantly learning something new each day, whether that was through doing a microbiological technique, talking with the post-docs, or chatting with the other interns.
I am extremely grateful to have been given the opportunity to be at the ASMG lab this summer. With the combined support of my mentor, Alex Post, and the ASMG lab’s Principle Investigator, Dr. Pitta, I got a chance to further explore my interests in agriculture and its evergrowing importance. While I had never fully thought about the interactions occurring within the microbiome, my time at the ASMG lab allowed me to have a greater understanding of the rumen microbiome and the bacteria behind the scenes.
This is part of a series of posts by recipients of the 2025 GAPSA Summer Internship Funding Program that is coordinated by Penn Career Services. We’ve asked funding recipients to reflect on their summer experiences and talk about the industries in which they spent their summer. You can read the entire series here.
