Microbiology

This elective science provides a foundational understanding of microbiology, and physiology of microbes with a particular focus on bacteria and fungi.

This subject consists of several topic areas:

- Techniques to study and distinguish microbes - microscopy skills- how to culture and grow bacteria using nutrient agar, differential and selective media. - examination of bacteria using chemical stains eg. crystal violet, Gram staining, Safranin & Malachite green to further study microbe morphology, cell wall structure
- Bacteria, Viruses and Fungi structure and growth
- Are microbes the key to the future?

Underlying these units is a key understanding of microbial cell function and reproduction. This course looks at the biology, and use of microorganisms from a everyday perspective and in sustainability.

Investigating microbes

Our students have been learning microbial techniques for identification of bacterial species. We have been working specifically on identifying Escherichia coli and Staphylococcus epidermidis. Below we used differential and selective media to identify the bacteria. Students were not told which bacteria was which. They were given the bacteria as labelled samples A and B. They needed to use their understanding of which species is differentiated or selected for or against using Mannitol Salt, CLED, MacConkey agar, Eosin methylene blue agar.

Prior to conducting this experiment, students had to research each of the agar types. They then could make a prediction about what they should or not see. They conducted their experiment and below are images of what grew or did not grow or what changed colour. Our students did a fantastic job of identifying our unknown samples A and B. Below is an example from a pair of our students and their record of their observations.

Figure 1: Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis) in Mannitol salt (MSA) media

Figure 1 displays a visual image of E. coli and S. epidermidis streaked in Mannitol salt (MSA) media. The left side, known as 'A' is identified as E.coli and the right side, known as 'B' is identified as S.epidermidis. As researched, E.coli would does not grow on the MSA media whereas the S.epidermidis does grow forming pink or colourless colonies. The E.coli formed no colonies while keeping the same orange media. However, as displayed in the image, the S.epidermidis instead changed the media to a yellow colour and formed yellow dotted colonies.

Figure 2: Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis) in CLED media

Figure 2 displays a visual image of E. coli and S. epidermidis streaked in CLED media. The left side of the plate identified as 'A' is E.coli and the right side, 'B', is S. epidermidis. During research it was found that E.coli would grow opaque yellow colonies with a deep yellow media and that S.epidermidis would not grow colonies on CLED medias. However, the S.epidermidis in 'B' has a green media and has grown yellow dotted and streaked bacterial colonies. The E.coli grew yellow streaked colonies with yellow media.

Figure 3: Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis) in MacConkey (MAC) media

Figure 8 displays a visual image of E. coli and S. epidermidis streaked in MacConkey. In the image the left side is E.coli and the right side is S.epidermidis. It is stated that E.coli should grow non-mucoid pink colonies with a pink media and that S.epidermidis should grow colourless and pale colonies. In the Figure 8, E.coli is seen with streaked pink colonies with pink media and the S.epidermidis is seen with dotted and streaked orange colonies and orange media.

Figure 4: Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis) in Eosin Methylene Blue Agar (EMB) media

Figure 4 displays a visual image of E. coli and S. epidermidis streaked in EMB agar, also known as Eosin Methylene Blue agar. The 'A' section on the left is E.coli and section 'B' is S.epidermidis. As researched, E.coli should have parts of of the media turn metallic green and S.epidermidis should not be able to grow on EMB agar plates. The S.epidermidis didn't grow any colonies as it was predicted due to research, however the E.coli grew streaked colonies but instead with black pigment and a dark red media.

Fig 5. Bacillus subtilus vegetative cells and endospores under a light microscope x1000 Magnification

Endospore staining

Here our students worked with two important chemical stains in Microbiology. Malachite green and Saffranin. These stains help students identify vegetative cells from endospores. This is an example from one of our students. The pink cells are the vegetative cells of Bacillus subtilus. The endospores are stained green. Endospores are tough and non-reproductive structures. Inside, there is a bundle of DNA, and the purpose of that tough outer layer is to keep the DNA well protected when the environment is not conducive for living and reproduction.

investigating virus structure

Have you ever wondered how washing your hands with soap help to kill particular viruses such as SARS-COV-2? We asked our students to investigate the science behind this. This is a visual representation that one of our students has put together to explain how soap can be effective against enveloped viruses.

Generalised structure of a virus. Viruses are either classified as non-enveloped or enveloped.

This image shows the chemical structure of soap.

Image showing the relationship with virus structure and the chemical structure of soap.

This is an example of a conclusion one of our students drew after their research.
Due to the recent covid-19 pandemic, washing hands and using hand sanitiser have been more crucial than ever. The article states that it was found that any kinds of soaps are effective to protect themselves from covid-19, due to membrane being composed of weak lipid molecules that allows soap to tear it apart and get rid of the virus before reaching the host cell. Although it is effective only if hands are washed properly and thoroughly. It was found that not all hand sanitisers are effective against the coronavirus. Only hand sanitisers that are at least 60% alcohol based, but due to alcohol being able to evaporate experts recommend buying 75% alcohol hand sanitisers. High percentage of alcohol means less water which prevents water interfering with protein function and prevents alcohol evaporating too quickly. Overall, washing hands with soap is seen as more effective compared to hand sanitiser as it is the safer option.

Are bacteria, Fungi, viruses our friend or foe

Our students had choice to work individually or in pairs as well as selecting a particular microbe of choice to investigate.

Their focus was on 'How can microbes (e.g. bacteria, fungi, viruses) be used to create a more sustainable future for our planet?'

Their goal was to convince the public that microbes are beneficial and the way of the future. Below are some examples of their infographics. Have they convinced you?