While working on my undergraduate degree, I studied an interesting strain of Staphylococcus epidermidis. This particular strain produced an unidentified substance, which was lethal to other Gram-positive bacteria. I immediately thought that this substance might prove advantageous in treating infections caused by antibiotic resistant bacteria. To begin investigating that possibility, I grew the strain of S. epidermidis near clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycinresistant Enterococcus (VRE), antibiotic resistant bacteria that plague hospital patients around the world. Amazingly, the strain of S. epidermidis was lethal to all of the isolates that it was tested against.
I then organized a group of undergraduates to assist me in characterizing the unknown substance. First, we chemically extracted the substance from the strain of S. epidermidis. We then used reverse phase chromatography to obtain a pure sample of the substance. Next, we determined the size, charge, and preliminary amino acid sequence of the substance using mass spectrometry. In addition, we tested the purified substance against a wide range of bacteria and human cell lines. From these preliminary results, we concluded that the substance is a small protein that had never before been discovered. We also confirmed its antimicrobial activity against all Gram-positive bacteria, including antibiotic resistant strains. In addition, we discovered that the protein had no observable toxic effects on human cell lines.
Concurrently, I designed and conducted experiments to determine which genes are associated with the synthesis and processing of the protein. After conducting a detailed literature review, I hypothesized that the genes might be located on a plasmid, a circular DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. I then developed a method for eliminating plasmid DNA from S. epidermidis that included growing it at high temperature and with a potent detergent. The cells that survived this harsh treatment were missing a plasmid and were unable to produce the antimicrobial protein. Sequencing the plasmid revealed several genes associated with the synthesis and processing of lantibiotics, a class of protein-based antibiotics. In addition, the plasmid contained a novel lantibiotic structural gene, the sequence for our newly discovered protein.
This study investigated a unique protein that could possibly serve as an alternative treatment option for antibiotic resistant bacterial infections. This project also revealed my own capabilities as a researcher. I relied heavily on published studies to design and conduct successful experiments. I also wrote my first grant proposal—a vital part of scientific research. As the project manager, I led and trained others in performing complex experiments, which helped me develop important communication and leadership skills. This study fueled my interest in biotechnology and its application to the medical field. I also realized that advances in formal scientific research allow our society to progress—an objective that I will continue to pursue in my career.