Isolating and Identifying Microbes on Human Skin During General Microbiology Laboratory
Location
SU-216
Start Date
1-5-2026 10:30 AM
Department
Biology
Abstract
In General Microbiology, students spend a semester characterizing microbial isolates from the human body or immediate environment. They work in teams of two to three members, conducting weekly tests involving different types of microscopy, staining exercises, and culturing microbes on various metabolic media. As part of this course-based research experience, we investigated whether a single bacterial species could be isolated and identified from skin behind the ear. A swab sample was collected and cultured to obtain an isolated colony, and standard microbiological methods such as staining, selective and differential media, and biochemical assays were performed. These were used to assess morphological and metabolic traits of the isolated microbe. We predicted that the isolate would be Staphylococcus epidermidis, a common Gram-positive skin commensal. The isolate showed the morphology and Gram-positive staining pattern typical of staphylococcal skin bacteria and displayed metabolic traits consistent with common skin commensals. Conversely, several biochemical reactions, including a catalase-negative result, conflicted with the expected profile of S.epidermidis, preventing a definitive identification. These results highlight how hands-on microbiological investigation reveals both the diversity of the human skin microbiome and the various laboratory limitations of phenotype-based identification. Future work will focus on repeating key assays, performing additional differential tests, and incorporating molecular methods to resolve the organism’s identity.
Faculty Sponsor
Emina A. Stojković
Isolating and Identifying Microbes on Human Skin During General Microbiology Laboratory
SU-216
In General Microbiology, students spend a semester characterizing microbial isolates from the human body or immediate environment. They work in teams of two to three members, conducting weekly tests involving different types of microscopy, staining exercises, and culturing microbes on various metabolic media. As part of this course-based research experience, we investigated whether a single bacterial species could be isolated and identified from skin behind the ear. A swab sample was collected and cultured to obtain an isolated colony, and standard microbiological methods such as staining, selective and differential media, and biochemical assays were performed. These were used to assess morphological and metabolic traits of the isolated microbe. We predicted that the isolate would be Staphylococcus epidermidis, a common Gram-positive skin commensal. The isolate showed the morphology and Gram-positive staining pattern typical of staphylococcal skin bacteria and displayed metabolic traits consistent with common skin commensals. Conversely, several biochemical reactions, including a catalase-negative result, conflicted with the expected profile of S.epidermidis, preventing a definitive identification. These results highlight how hands-on microbiological investigation reveals both the diversity of the human skin microbiome and the various laboratory limitations of phenotype-based identification. Future work will focus on repeating key assays, performing additional differential tests, and incorporating molecular methods to resolve the organism’s identity.