Microbiology misconceptions, troublesome knowledge & threshold concepts

As mentioned in the previous post, I’m hoping to start some online conversations with other microbiology educators soon. As I work on materials for my fall intro micro courses, I’d really appreciate the chance to talk about threshold concepts and misconceptions in microbiology. Here I’ve included some information about what these are, and what I’ve pulled together so far about introductory microbiology concepts.

Threshold with Giant Microbes
A threshold, if not a threshold concept.

I’ve been seeing more published evidence and increasing attention to the need for addressing student prior knowledge/misconceptions for effective learning, and the idea that there are key threshold concepts that must be mastered in order to proceed past the “threshold” to subsequent concepts in a discipline.  Threshold concepts have a number of characteristics, including that such concepts are considered troublesome, transformative, irreversible, integrative, and bounded. (Check out the references below, especially those from Meyer and Land, if you’d like to know more about threshold concepts.)

Some work has been done in a number of domains to identify threshold concepts and common misconceptions (TC/MC henceforth). (An interesting workshop “Troublesome concepts ACROSS the sciences” was offered earlier in the month at the Western Conference on Science Education by researchers at Dalhousie: http://ir.lib.uwo.ca/wcse/WCSEThirteen/july09/14 ) A number of people are working to identify TC/MC in biology – see Modell et al 2005, Taylor 2006, Ross et al. 2010, Smith 2012 for just a few examples. However, there is not a lot available (at least, that I have found) in microbiology, with the exception of interesting work by Marbach-Ad et al on host-pathogen interactions (e.g., see 2009 paper and others from this group).

The ASM has published a curriculum guidelines for introductory microbiology (http://www.asm.org/index.php/guidelines/curriculum-guidelines ; see Merkel 2012) which I found incredibly helpful in identifying what students should be learning. Identification of TC/MC could help us (as instructors) develop effective learning activities so that we can better help students progress through the curriculum.

So far, I’ve been collecting some TC/MC that I think are worth focusing on in course development. I’d really appreciate the input of other microbiology educators to expand/clarify this list … and, ultimately, share ideas of how to best address these items in our classes.  Below are my notes, such as they are (i.e., probably with many gaps/omissions).

There appear to be a number of TC noted already in biology/science (list below mostly based on Taylor 2006, Smith 2012) that apply to microbiology:

  • scale
  • randomness
  • complexity
  • variability/capacity for change
  • abstract concepts
  • biological processes (with some specific processes identified, including cellular respiration, redox reactions)
  • things/organisms that are too small to see (perhaps another type of “abstract” concept?) such as nucleic acids, microorganisms
  • transport across membranes (movement of things in/out of cell), including osmosis
  • the language of science itself

These make sense to me, and I am going to try to better address them in my teaching in future.

Some things I’ve noticed (and may have been noted by others but I haven’t yet come across them):

  • Appreciation of the wide variety of cellular life – how life is similar, and the differences that exist between different types of microbes. E.g., Bacteria vs. eukaryotes; the variety of eukaryotes which include microbes and macrobes.) Related misconception – all microbes are “the same”.
  • Bacteria (and many other types of microbes) are ubiquitous – they are (nearly) everywhere! (Including in you! On you! Definitely in your kitchen sink.) I think the difficulty in understanding (believing?) this also leads to difficulties in comprehending how easy it is to contaminate things/transfer microorganisms (i.e, understanding sterile technique). This is one of the concepts that I think microbiology laboratory exercises really helps with! Unfortunately, the majority of my intro micro students don’t take a class with an associated lab.
  • Some organisms (including many bacteria and archaea) grow/live in conditions that humans cannot (e.g., without oxygen).
  • Misconception: Germs are (all/mostly) bad. (Probiotic yogourt has gone some way to help ameliorate this!)
  • There are a few issues with understanding aspects of antibiotic resistance – in particular, there seem to be problems comprehending:
    Antibiotic resistance genes are natural, i.e., they are present in organisms that make antibiotics. (And the related fact that antibiotics are produced by microorganisms, without the intent of use by humans.)
    Antibiotic resistance genes are usually only valuable when antibiotics are present (e.g., in soil, in host, in lab when we are using those drugs). There seems to be a common misconception that antibiotic resistance genes are advantageous under all circumstances … and this connects to the next point …
    Antibiotic resistance genes have an associated cost – energy is required to maintain these genes and possibly a plasmid carrying them.
    Antibiotic selection selects for bacteria that already have antibiotic resistance genes (e.g., via random mutation). Probably the most common misconception that I’ve encountered is that susceptible bacteria become resistant as a direct result of – or response to – exposure to the antibiotic, that somehow the drug itself makes some bacteria resistant (or that the bacteria “decide” to become resistant).
    (To be fair, these relate to evolutionary concepts, and are not restricted to microbiology. Of course, if you’re teaching microbiology to a group of students that may not have a good grasp of evolutionary concepts, this issue lands in your lap! How much evolutionary biology do we need to teach nursing students?)
  • Students who have some comprehension of Mendelian genetics are often confused by aspects of haploid genetics (specifically, bacterial genetics). This may also affect how they view horizontal gene transfer – possibly looking at these processes as similar to what happens in diploid eukaryotic  sexual reproduction. (Redfield pointed out in a 2001 review that there are some major issues with the idea of suggesting HGT processes are equivalent to “sex”, and how scientists have interpreted bacterial phenomena in very human-centric ways.)
  • And, finally, I’m not sure if students actually have issues with this, but sometimes I do: Biology includes stuff that doesn’t fit the definition of life (viruses, viroids, prions).  Actually, I think understanding prions is difficult for many of us, not just our students. (I can still remember the look of wonder/amazement on the face of a former biology work-study student when I told her that prions are proteins!)

There are a number of concepts that I would categorize as “medical microbiology” that appear to be troublesome, and some may be threshold. Many relate to the immune system, vaccines, and host-pathogen interactions (including concepts identified by Marbach-Ad et al). I think I might discuss most of those separately, later.

I’m going to see if we can set up a Google Hangout next week … Will be keen to hear what other microbiology educators think about these!

References/suggested reading:

Marbach-Ad, G., Briken, V., El-Sayed, N. M., Frauwirth, K., Fredericksen, B., Hutcheson, S., … & Smith, A. C. (2009). Assessing student understanding of host pathogen interactions using a concept inventory. Journal of Microbiology & Biology Education: JMBE, 10(1), 43.

Merkel, S. (2012). The Development of Curricular Guidelines for Introductory Microbiology that Focus on Understanding. Journal Of Microbiology & Biology Education, 13(1). doi:10.1128/jmbe.v13i1.363

Meyer, J., & Land, R. (2003). Threshold concepts and troublesome knowledge: linkages to ways of thinking and practising within the disciplines. University of Edinburgh.

Meyer, J., & Land, R. (2006). Overcoming barriers to student understanding: Threshold concepts and troublesome knowledge. Taylor & Francis. [Routledge online store]

Modell, H., Michael, J., & Wenderoth, M. P. (2005). Helping the learner to learn: the role of uncovering misconceptions. The American Biology Teacher, 67(1), 20-26.

Redfield, R. J. (2001). Do bacteria have sex?. Nature Reviews Genetics, 2(8), 634-639.

Ross, P., Taylor, C., Hughes, C., Whitaker, N., Lutze-Mann, L., Kofod, M., & Tzioumis, V. (2010). Threshold concepts in learning Biology and Evolution. Biology International, 47, 47-54.

Smith, K. M. (2012). An investigation of student learning using threshold concepts in a first year cell biology course. MSc thesis. Available online: https://circle.ubc.ca/bitstream/handle/2429/41938/ubc_2012_spring_smith_karen.pdf?sequence=1

Taylor, C. (2006). Threshold concepts in Biology. In Overcoming barriers to student understanding: Threshold concepts and troublesome knowledge, 87. Meyer and Land, eds. Taylor & Francis. [Routledge online store]

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