by Amy Vollmer
Teaching microbiology is a terrific opportunity not just to introduce students to the world of microbes but also to help them to become critical thinkers and life-long learners. The challenges for us teachers are numerous: textbooks are getting thicker, yet the length of the semester is not increasing. How do we balance a sense of history with current discoveries? How can students absorb the diversity of species? How can we buttress key principle and concepts without just repeating ourselves? How can students ‘own’ rather than 'rent' the knowledge?
Creating assignments for my microbiology courses has given me the opportunity to address some of those challenges: With so many sources (credible and not-so-credible) at their fingertips, how can I ensure that students are not just going to cut and paste into a document of patchwork plagiarism? And properly cite reputable sources? How can I help them improve their writing without the dire prospect of re-reading multiple drafts of the same paper? How do I not saddle myself with a couple dozen multi-page papers and return them in a timely manner? We have all had the regrettable realization that the feedback we give on those end-of-term 10 to 20 page papers will likely not be read or incorporated or applied to the students’ future work. Finally, how can we help them develop sensitivity f for their communication with different audiences?
I have used a set of assignments, called "Adopt a Pathogen" in my Microbial Pathogenesis and the Immune Response course, renamed "Adopt a Bacterium" in my Microbiology course. I have presented this assignment, its rationale and grading rubrics at teaching workshops and have written about it Benjamin Cumming’s Great Ideas! In Teaching Microbiology (Volume 1, page 7) in an article on "Teaching Students to Write for Diverse Audiences". You will see that this strategy is applicable to other subject: Adopt in enzyme in biochemistry, adopt a gene in molecular biology, adopt an organelle in cell biology. My advanced students have even adopted two-component systems, riboswitches, or metabolic pathways. Here, the term ‘pathogen’ can be broadly applied, to encompass symbionts as possible adoptees.
By the end of the first week of classes, students sign up for the pathogen they will adopt (figuratively only). It cannot be one on a list of two dozen strains that we will study in the lab. The adoptions are unique and procrastinators are disappointed when their ‘favorite’ has been taken. The choice is of a bacterium (and not a eukaryote or virus). After I approve each adoption, they move to the next step. Each written assignment is limited to one page, double spaced, 12-point font. This teaches students to write succinctly. Proper use of references is required. The Literature Cited section can be on a second page.
Students start the semester complaining that one page is too much of a constraint, but by end of semester, they rise to the challenge to fill in that one page with as much information as possible! The first paper, due by the end of the following week, is about the name of the bacterium (what it means, if it has been changed and why) who discovered it and how, the general morphology of each cell and colonies (if they can be cultured on solid media). To help them develop fluency, during the second week, each student stands up and names his or her pathogen. Paper two, due two weeks later, focuses on growth: media, temperature, pH, electron donors and acceptors. Now students apply the general concepts from lecture and lab to their adoptee. Paper three is about genetics and genomics: (%G+C, number of ORFs in sequenced genome, number of chromosomes and plasmids; phage, transposons that are used for genetic manipulation). This assignment has changed most drastically, given that most of the adoptee’s genomes are now sequenced. This exercise highlights the fluidity of bacterial genomes and that horizontal transfer of genetic information is naturally rampant, not simply the whim of scientists. Paper number four deals with ecology and host/pathogen interaction. Subsequent papers can address one example of regulation of gene expression and the environmental circumstances that impact it.
Throughout the semester, there are opportunities for students to share 1-2 sentences about their pathogen: "mine has the highest G+C %", "mine has linear chromosomes", "mine can transfer its DNA to a plant genome." In this way, the entire class gets to hear about diverse microbes. I have heard many times, the conversations as students are exiting the classroom start with "hey, tell me more about your pathogen…"
Finally there are a couple of assignments that address diverse audiences. The first is a press release, to be issued as if there were their adopted pathogen were now to cause an epidemic. Students read aloud their press releases. In some years, I devote lab time to ‘press conferences,’ where the peers ask each student 3 questions after reading the press release. Other years, students work together to produce pamphlets for the third grade reading level. The subject of the pamphlets must be carefully vetted, and ‘scary’ and sexually transmitted pathogens are ruled out. My students have come up with great topics like the importance of hand washing, vaccines (not just for kids but for pets), ‘plants can get sick, too’, water purity, food safety. The theme is still generally microbiological, but what is key is the appropriateness of the subject. This assignment involves partnership with the right third grade teacher, the support of the school principal, and a letter from me to parents explaining the assignment and giving the kid the leeway to ‘opt out’ of the assignment.
Grading—my rubrics (or grading guide) for the papers to scientific audiences come straight out of the assignments themselves. Very straightforward. It includes proper use of references and writing mechanics (spelling, grammar, style, etc.). To help, I show students what publishers expect of us when we submit manuscripts. Those instructions make my assignment look quite simple! I keep track of the points that students missed. Obviously, content comes first. But if they make similar mistakes on the next paper (e.g., do not cite references properly or use less credible sources), they will have more points deducted the second time. I can help students improve their writing progressively, without reading the same thing again and again. I expect my feedback on their previous paper to be incorporated into successive papers. The size of the electronic stack of a couple of dozen one-page papers is not daunting at all; in fact, I look forward to read and learn about pathogens of which I do not know much about. The students can bundle all their one page papers together, combine the citations and end up with a nice mini-review of their pathogen, which makes for a nice ‘writing sample’ for prospective employers. To view my grading rubric for the first assignment, see here.
For grading the press releases, I engage our director of communications at the College and have her help me with a grading rubric. In some cases, she has offered to grade the papers! The third grade teachers and I work together: I visit the class a month ahead of time, explaining to the students that THEY will be grading college students’ papers! We talk about the writing skills that they are working on: spelling, capitalization, punctuation, sentence structure. They are excited to know that these are things that matter to college students, too. They help me develop a grading rubric of what they will be looking for: ‘not using big words that are not defined’, ‘good illustrations’, ‘clear information’. My own students spend some time learning about what is meant by ‘third grade reaching level’. By far, my students say that this is the most difficult assignment. A few told me that working on this assignment convinced them to enrolled in Education courses, spend some time teaching after college, or go into writing/illustrating science books aimed at children or the general public.
As a professor in a liberal arts college, coming up on my 32rd year of teaching (the 28th at Swarthmore), I continue to be impressed by the energy students bring to these assignments. They care about them because they establish some kind of personal connection to their adopted pathogen. I tell them that they will be the campus ‘expert’ on that pathogen. One student, who took the course reluctantly and adopted a symbiont, Rhizobium meliloti (now renamed Sinorhizobium meliloti), had a summer job assisting a technician who ran the scanning electron microscope at a university. All summer long, my student handled for imaging mostly inanimate objects. One day, someone brought in some root nodules. My student quickly recognized them to be from her adoption! She engaged the scientist in a conversation that revealed her knowledge and fluency, after which he mistook her for a graduate student. She was kind enough to come back that Fall and tell me that the assignment had been pivotal not only in building her confidence about microbiology, but in motivating her to pursue and earn a PhD years later!
Why do I love teaching microbiology? Because of what I learn from my students! Teaching is indeed learning.
Amy is Professor at the Department of Biology, Swarthmore College. She is a towering figure in microbiology education, having made numerous significant contributions to this field.