The utilization of an unconventional approach to introduce basic bacteriology in a medical school bridge program
ABSTRACT
Bacteria form an intense portion of reading and learning for students enrolled in microbiology education. As a part of the foundational course outline of bacteriology, bacterial classification is a significant topic of discussion. The purpose of our study was to analyze whether bacterial classification can be taught with a phylogenetic tree approach that might be more engaging and beneficial to student learners of microbiology. This methodology is unique compared to the conventional approach applied in introductory lectures of bacteriology that relies on morphology and Gram-staining to classify bacteria. The participants of this study were students enrolled in a two-semester medical school bridge program that offers a Master’s degree in Pre-clinical Sciences. We presented bacterial origin and classification in the light of evolution and used a phylogenetic tree to signify clinically relevant groups of bacteria. Students were also taught the traditional bacterial classification using Gram stains and morphology. Both methods of classification were delivered in a didactic classroom session considering equal time spent and utilizing the same format. An online survey was distributed to the students after the session to collect their feedback. The results from the survey showed that 74% of participants would prefer learning bacterial classification using a combined approach that includes both Gram-staining and morphology as well as the phylogenetic tree. When asked if the study of bacterial classification through an evolutionary tree diagram is a clear and concise way of understanding bacteria, 79% of the students either agreed or strongly agreed with this statement. Interestingly, the alternative phylogenetic tree approach was considered more engaging and regarded as a means to expand the clinical knowledge of bacteria by 78% and 71% of the students, respectively. Overall, our study strongly supports the use of tree-based classification as an additional method to improve the learning of medically important groups of bacteria at varying levels of education.
INTRODUCTION
A typical mode of introducing bacteriology in Master’s or medical education programs is through an instructive lecture with an emphasis on the classification of clinically relevant bacteria. The most frequently used bacterial classification is a combination of morphology and Gram-staining presented as a flowchart or table of Gram-positive, Gram-negative, and Gram-indefinite bacteria further separated at the species level by chemotaxonomic methods of differentiation (Fig. S1 and S2). A similar approach of classifying bacteria is also applied by clinical microbiology textbooks (1, 2). While Gram-staining data and morphology are important to memorize, a distinctive yet more engaging technique can be utilized to accomplish this objective in introductory discussions. We proposed that bacterial classification can also be taught via phylogenetic tree diagram of eubacteria as shown in Fig. 1. We hypothesized that this approach may provide a unique and more conceptual perspective to distinguish bacterial species and their characteristics in the light of evolutionary changes while appreciating the relationship among groups of bacteria.
Fig 1
While multiple theories have been proposed to rationalize bacterial evolution, a microbiologist tutor can choose either one of those theories as the basis for bacterial classification (5–7). The idea of bacterial evolution as suggested by Gupta et al. is widely recognized and was used as the primary resource to generate the eubacterial tree in Fig. 1. A phylogenetic visual, as in Fig. 1, categorizes eubacterial phyla into early or “ancestral” branches and late or “descendant” branches based on their distance from the root of the tree. This branching pattern provides conceptual details about bacterial membrane ultra-structures, growth conditions, possible divergences within groups, and a general idea of virulence factors contained by various species within a subdivision. For example, it can be conceptually clarified that early-branching ancestral bacteria such as Clostridia are strict anaerobes owing to their likely origin on Earth more than 3 billion years ago, when oxygen was not a part of atmospheric gases (5, 8, 9). However, late-branching bacteria such as Pseudomonas spp. and Escherichia coli evolved to become aerobes and facultative anaerobes, respectively, thriving in the presence of atmospheric oxygen. Further divergence within early-branching phyla such as facultative anaerobic growth of Staphylococcus spp. or aerobic growth of Mycobacterium spp. displays subsequent evolutionary development within these phyla as these species found their specific niches in mammalian hosts (10, 11). Likewise, the proposed visual also demonstrates that early-branching bacteria were single-membraned organisms with an outer cell wall that stain Gram-positive in contrast to evolving, later-branching bacteria, that enclosed their cell wall within another cell membrane to create a Gram-negative staining cluster.
Additionally, a comprehensive picture such as Fig. 1 illustrates an integrated collection of clinically significant commensal phyla as well as pathogenic species. Majority of microbiology textbooks enclose the “Normal Flora” topic as a separate entity from other sections of the book that describe bacterial pathogens (1, 2). For example, textbooks tend to refer commensal microbes by their pertinent phyla ranks, such as Firmicutes, Proteobacteria, and Actinobacteria, under the “Normal Flora” topic; however, phylum Actinobacteria or Firmicutes is seldom mentioned in the sections that describe Mycobacterium tuberculosis or Staphylococcus aureus (1, 2). Thus, it appears that the students learning through such a format will likely create a disconnect between the commensals and pathogens that share the same higher-level ranking. This could further obscure the students from understanding infection vs dysbiosis and the concept of how antibiotic treatment against a pathogenic bacterium can also affect commensal groups of bacteria that belong to the same phylum.
Furthermore, we suggest the subjunction of the theory of bacterial origin of eukaryotes along with the phylogenetic tree. This theory signifies an understanding of the relationship between prokaryotes and eukaryotes in the context of evolutionary development. Stimulating questions such as “How prokaryotic life started on Earth?,” “What was the last common universal ancestor (LUCA) of all life forms?,” “How eukaryotes ever come into being?,” and “What roles do bacteria play in our environment?” can motivate the students toward a comprehensive and committed understanding of the bacterial domain. While there are various hypotheses of prokaryotic evolution leading to the development of a eukaryote, a simple depiction of either one of those hypotheses is sufficient to familiarize with this subject issue. Figure 2 demonstrates the most widely accepted theory of “endosymbiotic origin of eukaryotes” and was used in our presentation. According to this model, archaebacteria and proteobacteria fused to create a nuclear-enveloped eukaryotic cell with mitochondria. Further adaptation such as inclusion of cyanobacteria to a eukaryotic cell is suggested to create a primitive plant cell (12–14). We proposed that this approach of understanding prokaryotic and eukaryotic characteristics will keep the students intrigued about the relationship we share as complex eukaryotes with the simpler prokaryotic life forms.
Fig 2
To evaluate if the proposed methodology would be beneficial for student learning in a medical school bridge program, we implemented the idea by presenting it to our Master’s class and collected qualitative data on how it was perceived by the students.
PROCEDURE
The students were given equally timed presentations on traditional method of bacterial classification followed by the new approach (approximately 10 minutes for each method). These sessions were integrated within a mandatory microbiology coursework large group lecture and were delivered using the same powerpoint format. Online survey was distributed after the lecture, and 35 out of 38 total enrolled students completed the survey. The results from the survey were examined for significance using χ2 analysis.
CONCLUSION
Results
To analyze how our presentation on the unique methodology was perceived, we examined the results collected from the post-large group session online survey. When the students were asked if they would prefer learning bacterial classification one way or the other, the majority (74%) answered that they would prefer learning basic bacteriology using a combined approach that includes both the traditional method and the evolutionary tree (Fig. 3). When asked if the study of bacterial classification through an evolutionary tree diagram is a clear and concise way of understanding bacteria, 79% of the students either agreed or strongly agreed with this statement (P value <0.001) (Fig. 4). Additionally, 70% of the students agreed that the phylogenetic tree method allows understanding of bacterial relationships at a phylum level, which makes it interesting to compare similarities and dissimilarities on a broader spectrum. The majority of students (67%) also believed that the evolutionary aspect of classification is more interesting and engaging (Fig. 5).
Fig 3
Fig 4
Fig 5
We wanted to inquire if the students considered that the new method has any clinical significance, therefore we asked if they considered that the tree mode of learning has the potential to expand clinical knowledge of bacteria and the use of antibiotics. Seventy-seven percentage of the students either agreed or strongly agreed with the stated fact (Fig. 6).
Fig 6
Additionally, we investigated the students' perceptions of the new approach and its perceived value across different educational levels including undergraduate, graduate, or medical school education. Table 1 shows the combined results of responses from all participants and the variation in preferences across the spectrum of educational stages. Toward the conclusion of the survey, we included an optional question inviting students to offer qualitative comments on the strengths and weaknesses of the session. These responses have been compiled and are presented in Table S1.
TABLE 1
| Education level | Strongly agree, n (%) | Agree, n (%) | Not sure, n (%) | Disagree, n (%) | Strongly disagree, n (%) | Total, n |
|---|---|---|---|---|---|---|
| Undergraduate | 9 (26.47) | 19 (55.88) | 5 (14.71) | 0 (0) | 1 (2.9) | 34 |
| Medical school | 9 (25.71) | 17 (48.57) | 8 (22.86) | 1 (2.86) | 0 (0) | 35 |
| Non-medical graduate school or postbac program | 9 (25.71) | 15 (42.86) | 8 (22.86) | 3 (8.57) | 0 (0) | 35 |
Discussion
This study was meant to research an interesting approach toward clinical bacteriology teaching in pre-clinical medical education. We infer that it is in student’s best interest to approach bacterial classification using Gram-staining and chemotaxonomic identity and support this method with a phylogenetic tree diagram. This study introduced an interesting approach toward clinical bacteriology teaching in a pre-medical education program. The idea of emphasis on teaching evolutionary microbiology has been previously proposed by other research scientists and educators (17–20). The traditional method of studying characteristics of bacteria limits the students to merely recall each species separately, without recognizing their higher-order taxonomy and relationship with other species in the same group. Our idea was to approach the bacterial kingdom with a more holistic view while categorizing them phylogenetically into various groups. Our study response supports that understanding bacteria with this perspective has the potential to create greater attention and interest in bacteriology learning. Since microbiology is not a pre-requisite for admissions in majority of osteopathic and/or allopathic schools of medicine, a comprehensive and meaningful introduction in pre-med or medical school coursework can create a lasting impact on the students’ perception of bacteria (21, 22). Our goal is to not only help the students as they comprehend microbes throughout their curriculum but also create a positive impact in choosing microbiology as a career path. Additionally, this approach provides a wider perspective of pathogens with a steered focus toward microbiome, which hitherto is not an element of introductory teaching curriculum in more than half of US microbiology courses (22).
SUPPLEMENTAL MATERIAL
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Traditional method of classification for Gram-positive bacteria.
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Traditional method of classification for Gram-negative bacteria.
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Qualitative comments obtained from student survey.
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Information & Contributors
Information
Published In
Journal of Microbiology and Biology Education
Volume 25 • Number 2 • 29 August 2024
eLocator: e00185-22
Editor: Stanley Maloy, San Diego State University, San Diego, California, USA
PubMed: 38785387
Copyright
© 2024 Iqbal and Onyedibe. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license.
History
Received: 7 October 2022
Accepted: 24 March 2024
Published online: 24 May 2024
Keywords
Contributors
Editor
Stanley Maloy
Editor
San Diego State University, San Diego, California, USA
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2024.
The utilization of an unconventional approach to introduce basic bacteriology in a medical school bridge program. J Microbiol Biol Educ.
25:e00185-22.
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