Improving accuracy in microbiology lab experiments: Common sources of errors and how to avoid them

In this article, we’ll highlight the most common sources of error and confusion and share how to help address them.

1. Pipetting errors

Micropipettes are one of the most basic yet essential types of equipment in microbiology labs. Students who have mostly used Mohr’s pipettes and volumetric cylinders for the measurement of chemical solutions at the high school level often feel confused about how to select the proper micropipette for precise handling when they get to college. Unfortunately, they also tend to lack knowledge about basic unit interconversions (L, mL, μL or g, mg, μg or M, mM, μM).

Ways to train students how to pipette:

• Linking to free videos from other universities that describe the different parts and handling of micropipettes.
• Showing students online webinars created by industry: 

• Example-1: Mettler Toledo Workshop on Good Pipetting Techniques.
• Example-2: Eppendorf Webinar on Maintenance of Micropipettes.

• Anticipating the common pipetting errors students make and giving them pre-lab practice handling micropipettes with Labster’s simulation Pipetting: Master the technique virtual lab.

Figure: Scene from Pipetting: Selecting and Using Micropipettes Simulation from Labster. Image Credit: Labster

‍3. Staining errors

Learning microbiology would be incomplete without understanding staining practices. With a variety of stains available in the lab setup, students can stumble while choosing a stain according to biological tissue. They may also fail to grasp the science and mechanism of action of different stains. When the staining method involves following a series of steps, any error in the sequence can also result in failed results. A lack of understanding of the microbiological world (bacteria, viruses, etc) is also a common issue that leads students to make errors.

Ways to train students how to do a stain

• Teaching about the microbiological world and the diversity of life forms like Gram-positive and Gram-negative bacteria using virtual 3D models and virtual microscopy experiments.
• Taking students on a virtual field trip and tapping into their natural curiosity by involving them in interactive learning games.‍

3. Sterility errors

Microbiology labs and benchtops require absolutely sterile conditions. Carelessness in microbiology lab handling can wreak havoc in the designed experiments. This applies to everyone from amateurs to experienced students. Lack of exposure and experience in working with laminar flows, biosafety cabinets, autoclaves, etc. can be a major source of errors in the lab. Unfortunately, it’s not always practical to offer in-person demonstrations that show how to deal with errors like microbial contaminations, culture spills, and problems in aspiration systems.

Ways to train students how to work in sterile conditions 

• Sharing some of the free community resources available via the ABSA (American Biological Safety Association).
• Using virtual labs like Biosafety and Pasteurization and Sterilization as pre-lab exercises to get your students acquainted with the basic rules of working in biocontainment labs. 
• Providing an experiential learning opportunity where students can take on the role of a lab assistant in a gamified scenario. 

Figure: The ABSA (American Biological Safety Association) conducts an Annual Biosafety and Biosecurity Conference for highlighting biosafety and sterility issues. Image Credit: ABSA

‍4. Instrument handling errors 

Without a doubt, microscopes are the most important instruments in microbiology labs. There are many specialized types of microscopes, and different microscopes may require different staining practices, provide different visualizations, and have different working principles. It would be very unlikely for a student to have had prior experience working with the exact instrument they’ll need to use in any given microbiology lab experiment, especially when a highly sophisticated microscope is required. 

Ways to train students how to use a microscope

• Teaching about the major differences between microscope types using virtual labs that simulate hands-on lab work. (Fluorescence microscopy) (Light microscopy) (Confocal microscopy)
• Including the scope of microbiological studies in lesson plans using updated journal articles.
• Introducing students to real-world applications of microscopy at public industry conferences and workshops

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Figure: Images from Fluorescence Microscopy Facility at EMBL. Image Credit: EMBL

5. Microbial Culture errors

Microbiological research relies heavily on the culture of microbial species. Students often get confused while making culture media, calculating colonies, and characterizing microbial growth. Their uncertainty about constitutions, calculations, and proper technique can lead to errors. Building up their foundational understanding of serial dilutions, molar calculations, and streaking techniques can help them avoid mistakes and keep their experiments running smoothly. 

Ways to train students how to make microbial cultures

• Taking your students on an inquiry-based journey to quantify bacteria in Labster’s interactive Bacterial Quantification by Culture simulation.
• Using illustrations and infographics to educate your students about the different phases of microbial growth.
• Use of virtual lab features to help your students explore various aspects of microbial growth, immunological techniques, etc. (Virtual Lab-1) (Virtual Lab-2)

Conclusion and additional resources 

Repeated cycles of contamination or culture failures can make microbiology labs seem very tedious. If faculty can help students build a deeper understanding of why they are doing a particular microbiology experiment, they can help them build the confidence to avoid lab errors.

Labster simulations support microbiology educators in conveying important theoretical concepts as well as lab skills - and the engaging interactives make learning a lot less tedious. Microbiology educators can also offer their students easy access to related content from Labster’s Microbiology Simulation Course Package.

Questions for reflection:

• Which microbiology lab techniques will be new to your students this term?
• Which new teaching resources would be most relevant to help your students avoid microbiology lab errors?

References

1.      Eswarappa Prameela, S., McGuiggan, P.M., Brusini, A. et al. Looking at education through the microscope. Nat Rev Mater 5, 865–867 (2020). https://doi.org/10.1038/s41578-020-00246-z

2.      World Health Organization. (2004). Laboratory biosafety manual. World Health Organization.

3.      Perdigao, J. O. R. G. E., Lambrechts, P., & Vanherle, G. (2000). Microscopy investigations: techniques, results, limitations. Am. J. Dent, 13, 3D18D.

4.      Rouf, A., Kanojia, V., Naik, H. R., Naseer, B., & Qadri, T. (2017). An overview of microbial cell culture. Journal of Pharmacognosy and Phytochemistry, 6(6), 1923-1928.

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