Objectives: Recognize common types of household molds; perform a simple controlled experiment testing the effects of antifungal compounds on mold growth; analyze, interpret, and report the results of an experiment.
Instructions
“If they can make penicillin out of moldy bread, they can sure make something out of you.” –Muhammad Ali
We live in a sea of spores. Fungal spores, to be specific. You might not see them—in fact, if you do see them, I’d be a bit concerned—but there they are, suspended in the air around us. While some may be agents of disease, either directly or by triggering allergies or asthmas, most fungi are friendly decomposers, working hard to provide a vital service in all kinds of habitats. But yeah. Even a lot of the good ones produce deadly toxins, so… that’s fun. In this lab experiment, we’ll be examining some common household molds and testing the effects of antifungals on their growth.
For this lab activity, you’ll need the following supplies:
- 6 slices of plain white bread (from the bakery section, without preservatives)
- 6 transparent, regular-sized Ziplock sandwich bags
- Athlete’s foot or jock itch cream (contains terbinafine or clotrimazole)
About 1.5 or 2 weeks before collecting data and writing your report, take six slices of plain white bread and, without tearing them, wipe both sides of the bread on your kitchen counter (in an area that was not recently cleaned). Place three slices each in separate sandwich bags labeled “control group.” For the other three slices, carefully spread about ¼ tablespoon of antifungal cream in a thin, complete layer on each side of each slice of bread, like butter; make a note of the active ingredient and concentration because this will be important to include in the methods section of your report. Place these three slices each in separate sandwich bags labeled “experimental group.” If you want, you can increase the level of replication by adding more slices of bread to each group, but three slices per group is the absolute minimum. Store the bread bags in a warm, dark area with normal ventilation (in a cabinet is fine, just not in a tightly sealed container). After seven days, remove the bags and inspect them for mold growth. Take pictures of each slice of bread, make an effort to identify the molds that are present (it’s probably just Rhizopus or maybe also Penicillium, but feel free to simply describe the species present, you don’t need to be 100% of their actual names). Next, estimate the total surface area covered by fungi on each slice, which will range from 0% to 100%, and record these numbers in your lab notebook (or directly onto your computer). With this data, you’ll need to perform a t-test to compare the average surface area covered by fungi in the control vs. experimental groups and create a graph that shows the differences (average ± standard error for each of the two groups).
❗️Safety note: Keep the inoculated bread and antifungals away from children and pets. The antifungal creams may be toxic if consumed, and you don’t know what kind of dangerous fungi might be growing on your bread. After sealing the sandwich bags, they should not be reopened. Throw them directly into the trash at the end of the experiment.
Your lab report will include an introduction, methods, results, discussion, and references. Additionally, you’ll need to include an abstract (“summary”) and acknowledgements (did you have any help/support, e.g. special thanks to my family for supporting my academic adventures). The introduction is a brief overview of the background and reasoning for the project; in this case, who are the fungus among us, and how effective are over-the-counter antifungals at suppressing their growth; include in-text citations to any references you use. For the methods section, you should explain the experimental design in enough detail for someone to be able to repeat it (the overall design [control and experimental groups, level of replication], type/brand of bread, concentration/amount of antifungal applied, software/statistics used for analysis, etc.). Next, the written results section should include two figures and one table as well as a t-test comparing fungal growth between the control and experimental groups; Figure 1 should be a photo showing one slice of bread from each group at the end of the experiment (pick a “representative” slice that’s closest to the average for that group), Table 1 should list the species of fungi you identified in each group (control vs. experimental groups), and Figure 2 should graph the surface area covered by fungi (average ± standard error). The discussion should provide an interpretation of your findings and the broader context and/or applications; you’re required to include two peer-reviewed references with in-text citations. Finally, full references in the references section should be organized alphabetically by the surname of the first author; use hanging indents and follow all APA formatting rules [Lastname, F. M. (Year). Article title in sentence case. Journal Name, volume#(issue# if there is one), page range xx–xx. DOI].
Deliverables
A 900-word (~2.5 pages, including figures) typed report. Use 12-point doubled-spaced Times New Roman font. References and headings are excluded from the word count. No title or cover page is necessary, but there should be headings for the Abstract, Introduction, Methods, Results, Discussion, Acknowledgements, and References sections. References should be formatted in APA style, which includes the use of in-text citations. Name the file “Fungus_Lastname” and upload as a standard Word document (.docx) or PDF (.pdf).
