if ever allow students to inoculate fast food. Moreover, our screening
exercise was unique in allowing students to select their own food
items and investigate the nutrient makeup of those items before predicting results. These exercises were developed under the assumption
that allowing students to work with food items they habitually consumed and that they themselves selected would engage their interest
and lead to effective learning. In spring 2018, we used surveys and
normal assessments in our course to assess students’ content knowledge and attitudes toward (1) Internet stories, (2) fungi, and (3) fast
food. We demonstrate the success of these exercises over several
semesters and encourage the readers to adopt these exercises and
develop similar exercises.
Upon completion of both exercises, students should be able to
• evaluate accuracy and reliability of online information,
• identify dependent and independent variables of an experiment,
• formulate a hypothesis to answer a question,
• experimentally test the hypothesis and conclude whether it is
• critically evaluate whether their own nutritional choices are
These exercises are appropriate for high school biology students or college students in introductory or nonmajors biology,
microbiology, or nutrition courses. More specifically, the exercises
apply three-dimensional learning as defined by the Next Generation
Science Standards (NGSS) (NGSS Lead States, 2013). After the exercises, high school teachers should be able to assess whether students have met Life Science Core Idea standards and assess their
progress in mastering Science and Engineering Practices and Crosscutting Concepts (Table 1).
Exercise 1: Experiment Procedure &
During the spring 2018 semester, our introductory biology class
(21 students) was split into two groups, one of which (Group 1,
11 students) inoculated hamburger patties from an international
fast-food chain while the other group (Group 2, 10 students) did
not. The hamburger patty group was further subdivided into three
teams (3–4 students per team), each of which inoculated five patties of the following three types: plain patties, plain patties with
cheese, and patties with ketchup and mustard. Patties were cooled
to 15–20°C before inoculations. The other group was subdivided
into three teams, two of which inoculated five slices of off-brand
sliced white bread from a local supermarket and one of which inoculated five 100 mm plates of Sabourad dextrose agar (SDA; Carolina Biology Supply Company, no. 786781). To be consistent, 60
mm disks of each type of food sample were cut and placed in Petri
We selected Rhizopus stolonifer cultured on potato dextrose agar
(Carolina Biological Supply Company, no. 156223) for our exercises because of its ubiquity, availability, and low potential to cause
harm to students. Samples were inoculated by punching a 3 mm
circular plug of R. stolonifer mycelium from the plate and transferring the plug to the center of the food disk or plate with forceps
(Figures 1 and 2). Punches and forceps were sanitized with ethanol
between samples. All inoculated samples were sealed with Parafilm
and incubated 96 hours at 25°C, the temperature indicated by the
vendor. Students recorded the presence or absence of visible
growth in sealed plates and used digital calipers to measure the
diameter of the mycelium at its widest point. Sealed plates were
autoclaved afterward according to standard safety guidelines.
In our 2018 trial, R. stolonifer grew on all of the plain patty
samples and SDA plates, grew on one patty with cheese, and
did not grow on the patties with condiments or on the bread.
Table 1. Alignment of the learning goals for our two exercises with the Next Generation Science Standards
(NGSS Lead States 2013).
Science & Engineering Practice Disciplinary Core Idea Crosscutting Concept
Analyzing and interpreting data
Mean mycelial diameter is used to
determine whether fungal growth is
supported or inhibited.
LSI-C: Organization for matter and
energy flow in organisms
Fungi are heterotrophs that break
down organic matter to acquire
matter and energy.
There are specific food items and their
components that tend to support or inhibit
Hypothesize whether fast-food
components will support or inhibit
Structure and Function
Fungi are composed of filamentous hyphae
that maximize surface area:volume ratio.
Engaging in argument from evidence
Defend or critique the claim that fast
food does not decompose.
Obtaining, evaluating, and
Evaluate the accuracy of the mold myth
and similar online claims.