There are many hypotheses to explain the lack of diversity in science. One of the most compelling arguments for fields that involve outdoor research (e.g. geosciences, environmental microbiology, climate science) is that students of color feel intimidated by the outdoors. As a result, underrepresented minority (URM) students are dissuaded from pursuing fields in the natural sciences. This effect is an important piece of the “leaky pipeline” paradigm that stymies diversity in academia.

Public school curricula lack programs to educate students in the outdoors (i.e., placed-based learning). Stu- dents often learn about environmental microbiology and earth sciences from behind desks while the phenomena they study happen all around them: In their backyard, local park or gardens. Students of color (SOC) are even less likely to feel comfortable being, let alone learning, in outdoor spaces. To address this disparity, a group of Caltech students has formed an organization called GO-Outdoors ( GO-Outdoors is an outreach platform connecting graduate students with local teachers in the Pasadena Unified School District (PUSD, a majority SOC community) to generate field trips and lesson plans that move the classroom outdoors, enabling students to learn about the environment and engage with nature. This ROCS project was designed and implemented in collaboration with the GO-Outdoors organization.

We founded the GO-Outdoors program at Caltech to address outdoor inaccessibility within our own community. Caltech is located in a public school district where >70% of students are URM and >60% of students receive free or reduced meals. Our organization designs and organizes place-based learning opportunities in collaboration with K-12 teachers to get these students interested in the outdoors. The largest barrier to pro- viding these programs to local classrooms is funding for transportation, equipment, and food. We used the alumni ROCS funding to implement a pilot program centered around environmental microbiology with a focus on sustainable and collaborative community outreach.

Download the Field Trip Guide and/or the Lesson Plan.

People involved: Elliott Mueller (Caltech, Alumni of Microbial Diversity ATRC), James Mullaho (Caltech), Korbinian Thalhammer (Caltech).
People involved: Elliott Mueller (Caltech, Alumni of Microbial Diversity ATRC), James Mullaho (Caltech), Korbinian Thalhammer (Caltech).


At the onset of this project, we defined a broad, long-term goal: To make scientific fields based in the outdoors more accessible to students of color. The more detailed learning objectives were two-fold: 1.) Demonstrate that microbial life is ubiquitous and diverse 2.) Learn multiple scientific tools to make microbial life observable with the naked eye.

In the “Finding the Beauty in Microbial Diversity” program, high school students would explore a local trail to learn about basic microbial and ecological phenomena. They each collected their own samples driven by their individual interests and used those samples to perform in-class laboratory experiments. With this program, we hoped to break through exclusionary barriers that keep students of color from working in the outdoors. Ultimately, we hope to increase the diversity of students applying to college for field-based sciences.

The inspiration for this project was drawn from both my experience as a student in the Earth Sciences and as a student at the MBL. Being in the outdoors was an important part of the path that led me to be an Earth scientist. It was the MBL course that revealed to me how the link between microbiology and geoscience can be simply and effectively demonstrated without arcane knowledge or a formal education in either subject. All of the activities I used in this project we performed on the Microbial Diversity course in 2021. The instructors on that course also emphasized the utility of these experiments for outreach programs.

Summary of Program

This program was broken into two major activities: Field-based lessons and in-class laboratory activities.

Field-based Lessons

students and foldscope
Figure 1: High school students are taught by Caltech graduate students how to examine microscopic life using the Foldscopes

On March 17th, fifteen AP Biology students from the John Muir High School (Pasadena, CA) took a bus from their school to the local San Gabrielino trail. This trail is less than 2 miles from their high school. The proximity was intentional, as we centered our lessons around ”place-based” learning, a pedagogical theory that focuses on making observations and inquiring about one’s local surroundings. At the trailhead, the students were introduced to the idea of microbial life with a ”Toilet Paper Ruler” activity. Serving as a to-scale ruler where each sheet represented 3 microns, a roll of toilet paper was unspooled by the students. Taped markers throughout the roll represented different sized cells (bacterial, animal, etc.) as well as some other representative small objects, including the width of a hair and the length of an ant. The students were then asked to estimate the number of bacteria in a gram of soil based on their size. The objective of this activity was to demonstrate that microbes are small organisms but they can have a large impact when there are many of them, making them an important part of the Earth’s biome.

After hiking for 30 minutes, the students were asked to split into groups of five and were rotated through three exercises:

  1. Field Microscopy:

Students were given Foldscope microscopes to observe microscopic life in natural samples. Foldscopes are hand- held, paper microscopes that achieve >100x magnification. With these, students made many observations, including plant cells in the stems of leaves and algal cells in algal blooms found in a nearby stream.

testing stream water
Figure 2: Caltech volunteer (right) teaches a student how to properly inoculate a plate with drops of stream water and recommends strategies for labelling her plate.
  1. Agar Plate Inoculation:
plate inoculated with student's breath
A plate inoculated with a student’s breath after one week of incubation. Bright, isolated colonies of pink, red and yellow were found.

Students were asked to inoculate two agar plates with an environmental sample of their choosing. One plate contained only nutrient broth. The other contained nutrient broth plus glucose. They chose their environmen- tal inoculate, spread these on their plates, and labelled the plates with sample descriptions. After one week of incubating at room temperature or 4C, they made observations of their plates, the number and diversity of colonies, and the differences between the conditions. Students chose an impressive range of samples from alga blooms, to individual minerals to leaves from the local trees. This activity pushed them to consider why different samples might be interesting while learning a realistic technique for observing and isolating microbes from the environment.

  1. Winogradsky Column Sample Collection:

Students collected 200 grams of soil, leaf litter or any other environmental sample they chose for inoculation of Winogradsky columns. Their samples were stored in small plastic jars labelled with their sample information and name.

The field trip lasted for 3.5 hours in total.

Figure 3: Caltech volunteer (left) teaches about Winogradsky columns and explains the exercise. We used a premade column as an example.
Figure 3: Caltech volunteer (left) teaches about Winogradsky columns and explains the exercise. We used a premade column as an example.
Students taking samples. The AP Biology teacher can be seen observing the activities in the center.
Students taking samples. The AP Biology teacher can be seen observing the activities in the center.

In-Class Experiments (Part 1)

One week after the field trip, three Caltech graduate students visited the John Muir High School for an hour and a half. Here, the students were split into two groups:     

  1. Agar Plate Observations:
algal cells under microscope
Image of an algal cell observed under the microscope.

Students were handed back their plates which had been stored at Caltech while their colonies grew to the point where they could be seen with the naked eye. Students were given a worksheet (see attached documents)asking about the number and diversity of colonies. Several students pointed out where two colonies were occupying the same space on the plate with a clearing between them. With guidance they drew conclusions about microbial interactions and how these might play out in the environment and in the human body. After macroscopic observations, Caltech volunteers brought out a microscope capable of observing bacterial cells (purchased with MBL ROCS funding). Students learned how to make glass slides of individual colonies and observe their cell morphologies under the microscope.

  1. Winogradsky Column Observations:

Students were given a recipe for generating Winogradsky columns (see attached documents). They mixed their environmental samples with water to bring the microbial cells into suspension and then poured out the water onto diatomaceous earth. To this slurry they added pre-weighed aliquots of sulfur, nitrogen, phosphorus and

This gave students an understanding of which elements cells require to grow and bloom. This activity was designed to teach another ecological tool for observing microbial communities growing and engineering their environments. Winogradsky columns, which cultivate natural, polymicrobial communities, were juxtaposed by the agar plate experiment (cultivating individual species in isolation) to demonstrate the range of microbiological tools.

In-Class Experiments (Part 2)

In mid-May, we will return to the classroom to make observations of each student’s Winogradsky columns after they have bloomed. This will once again be accompanied by microscopy.

Winogradsky columns
Winogradsky columns


Learning objectives

The major goals of this project were met. Students were given pre- and post-surveys before and after the field trip activity to assess what they had learned. We found that students self-evaluated knowledge of microbial diversity and tools for microbial ecology both increased. Through the in-class activities, students demonstrated a genuine understanding of how these techniques could help them see the microbial world. They also expressed interest in pursuing this kind of science in the future.

Figure 6: Results from student self-evaluation surveys taken before and after the field trip demonstrate an increase in their understanding of microbial diversity and microbiological techniques for cultivation and obser- vation.

Community relationships

I believe the larger impact of this activity was in building a relationship with PUSD. The GO-Outdoors group has been working hard to build and pilot field trips for the past year, but this was our first field trip and lesson with a classroom. Thus, it was our first experience interacting with the school district directly. However, when the teachers at John Muir High School learned of our program, they enthusiastically supported it. Already the teacher we worked with (Alexandra Gonzales) has requested that we run this program next year and for more classrooms including Introduction to Environmental Science, Introduction to Biology, and AP Environmental Science. Through the John Muir High School we were also able to make connections with other under-resourced schools in the district.

results of student survey
Figure 6: Results from student self-evaluation surveys taken before and after the field trip demonstrate an increase in their understanding of microbial diversity and microbiological techniques for cultivation and obser vation.

Sustainable outreach

Another important impact of this work is its institutional memory. Often outreach activities are one-off expe- riences where scientists enter a community momentarily and then retract. This paradigm erodes trust with the community. During this activity, we openly collaborated with the teachers to fit their needs. We found dates when teachers were overwhelmed with other obligations and found content that would augment their curriculum. As I organized the logistics of these activities (i.e. school bus rentals, supply purchases, planning meetings with school administrators and teachers, etc.), two younger graduate students (Korbinian Thalhammer and James Mullaho) shadowed me and helped organize the event. This way, the program can be run when I am no longer at Caltech. Moreover, even with the small grant supplied from the ROCS, I purchased enough equipment to iterate this program at least 10 more times (excluding the cost of transpiration). Outreach efforts are cost efficient and, after the initial investment in relationship building, organizing and purchasing, can be a low-effort endeavor. Thus, in multiple respects, I found this experience to be largely successful!