Of Biofilms and Beehives: An Analogy-Based Instructional Tool to Introduce Biofilms to High-School and Undergraduate Students

The concept of biofilms and biofilm-based research is largely absent or minimally described in high school and undergraduate life science curriculum. While it is well-established that microbes, such as bacteria and fungi most often exist in multicellular biofilm communities, descriptions in standard biology textbooks continue to focus on the single-celled form of microbial life. We have developed an analogy-based instructional tool to introduce and explain biofilms to high school and undergraduate students. The module employs an analogy with beehives, given that biofilms and beehives are both ‘superorganism’ states, to explain key biofilm features such as development and structure, chemical communication, division of labor and emergent properties. We delivered this analogy based learning tool to a cohort of 49 high school and undergraduate students, and based on participant feedback and learnings, present a formal evaluation of the instructional tool. Further, we outline prerequisites and learning approaches that can enable the delivery of this module in classroom and virtual learning settings, including suggestions for pre-lesson reading, student-centred interactive activities, and specific learning objectives. Taken together, this instructional analogy holds potential to serve as an educational tool to introduce biofilms in high school and undergraduate curricula in a relatable and comprehensible manner.


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Module 4: Emergent properties in beehives and biofilms 2 0 0 As 'superorganism' states, beehives and biofilms exhibit collective or emergent properties, that are not displayed 2 0 1 by individual organisms (68). In honeybee colonies, a well-known emergent behaviour is thermoregulation (69), 2 0 2 that relates to the ability of the honeybee colony to survive as a whole. At low temperatures, bees tend to move 2 0 3 closer together and share body heat. Since the centre has more heat, and younger bees cannot shiver, they move 2 0 4 inwards. Adult bees shiver to produce heat and move to the middle and outer layers. This heat warms the whole 2 0 5 hive ( Figure 4A). As the heat in the centre increases leading to a situation of excess heat, the young bees move to 2 0 6 create channels of air exchange, allowing heat from inner regions to flow out towards the older bees. This 2 0 7 combined effect enables the hive as a whole to stay warm, a critical factor for survival of the colony.

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An important emergent property of bacterial biofilms, that differs from free-floating cells, is increased tolerance to 2 0 9 antimicrobials. This results from specific properties of bacteria in the biofilm, as well as the biofilm matrix itself 2 1 0 (2). The EPS matrix reduces diffusion of antimicrobial agents into the inner parts of the biofilm (2). In the 2 1 1 bacterium Pseudomonas aeruginosa, components of EPS such as polysaccharide and extracellular DNA, form 2 1 2 interactions with antibiotics and impede their penetration through the matrix (70). Bacteria in biofilms also adopt 2 1 3 properties of slow growth and dormancy, with reduce their susceptibility to antibiotics, such as penicillin, that act 2 1 4 on actively-growing cells (71). One type of slow-growing cells in biofilms are persister cells, that exhibit high-2 1 5 level tolerance to antimicrobials (72, 73), but can revert to a growing state and repopulate the biofilm once 2 1 6 treatment is stopped ( Figure 4B).

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Suggestions for determining student learning 2 1 8 Student learning was assessed using pre-session and post-session feedback forms via Google forms. The forms 2 1 9 used a combination of multiple choice and free response questions. Pre-session feedback included information on 2 2 0 participant demographics, prior science and biology courses, use of pre-session reading materials and familiarity 2 2 1 with brood concepts of the analogy. Post-session feedback assessed learning of the content delivered in the 2 2 2 modules and stated learning objectives. Students were provided time to fill these forms before and after the  In the pre-session form, students provided data related to demographics, educational level, previous science or 2 2 6 biology courses, familiarity with biofilms and beehives and use of pre-session reading materials (Figures 5 -7).

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Students learning data was collected in response to specific content-based questions, anecdotal feedback in  There are no safety issues associated with the delivery and adoption of this lesson. The analogy-based instructional tool was delivered on two separate occasions (session time 90 minutes) via a 2 3 5 virtual format (webinar) to high school students (24 students; 13-18 years old) and undergraduates (25 students) 2 3 6 across India. While the content and delivery were prepared with these groups in mind, the session for school 2 3 7 children was open to younger age groups. High school students were from different schools across the country,  Post-session feedback was obtained from 46 respondents, as compared with 49 respondents in the pre-session 2 4 5 feedback. It is unclear as to why 3 respondents did not respond or may have left the session prior to completion.

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Based on feedback after the session, 74% (n=34/46) students reported the closest meaning of the term 'analogy' as 2 4 7 comparison and 26% as similarity ( Figure 8A). This is in contrast to feedback obtained prior to the session, and    Data generated in this study, including anonymized feedback data, will be made available by the authors' upon 3 1 4 request.

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Respondent Feedback 13 years, 7 th grade "The interactive session, the way we imagined different things and how we learnt in a fun way" 15 years, 9 th grade "We ended up learning about two things at the same time. It's easy to correlate between the two topics because we have better understanding of one of the two topics. We could think about a wider range of aspects and come up with better questions" 20 years, undergraduate "It used a phenomenon that we are familiar with and could therefore easily relate to. The information was engaging and well placed to ensure that our attention didn't waver too much. The method of explaining was very simple and to the point"

years, undergraduate
"It was more engaging as I was trying to find similarities and difference between two subjects that were compared. It made the understanding of biofilms much easier and interesting"     the two entities. In honeybee colonies, a well-known emergent behaviour is thermoregulation, which relates to the 5 6 7 ability of the honeybee colony to survive as a whole. At low temperatures, bees tend to move closer together and 5 6 8

Scouting behavior
share body heat. Since the centre has more heat, and younger bees cannot shiver, they move inwards. Adult bees 5 6 9 shiver to produce heat and move to the middle and outer layers. In biofilms, an important emergent property is the  Adult bees move to middle and outer layers of the hive and shiver to produce heat.
Young bees cannot shiver, they move towards the inner regions of the hive.