Question

 

1. In a hypothetical situation, you are asked to pick 4 locations of your choice and test them for presence of bacteria by swabbing nutrient media plates.  You have to decide which locations you would like to test.  Locations may include your environment and your body.  You may not choose more than 2 body locations.

2. Explain why you picked those 4 locations and describe your hypothesis or question.    An example of a question: Are there more microbes on a kitchen sink or a stove?

3. List two conditions you will use to incubate your swabbed petri plate. For e.g. under what temperature, oxygen conditions will you incubate the plates? (To answer this question, think about the environmental conditions that exist around the locations you have selected. Bacteria that grow in these locations will adapt to those environmental conditions.)

4. Predict what you expect to see on your plates. (e.g. relative numbers, diversity).  Any prediction is valid. The logic supporting your prediction is what is valuable.

5. You are trying to isolate an important bacteria called Nitrobacterwinogradskyi from soil.  This bacteria is important in making nitrogen available in soil for use by plants.  Design an experiment to isolate this bacteria from soil.  Your experiment should include some basic microbiology technique that allows quick separation of this bacterium from the rest of the soil sample. Also, how would you verify that you have achieved purification? (Do not complex molecular techniques such as DNA sequencing as a part of your protocol)

6. After performing your experiment in step A, you suspect that your sample is not completely pure, and is contaminated with another common soil bacterium Bacillus subtilis.  What should your next step be to separate Nitrobacter from this contaminant?

7. Define a bacterial colony.  Will all members of the colony be identical to the original bacteria that started the colony?

Answer 1

1. The swabs can be taken from:

• nasal mucosa
• bathroom floor mat
• refrigerator water collector
• mobile phone case grooves

2. Nasal mucosa is habitat of many microbes in the inhaled air. Bathroom floor mat is too accessible for any kind of bacteria in that niche. Refrigerator water collector is a periodically spilled off stagnant water collector that can easily house many microbes. Mobile phones being handy and kept on various surfaces in a day, are supposed to shelter many different species of microbes. These are selected due to the mentioned reasons as well as they seems to be less studied except nasal mucosa, when compared with some usual sites like armpits, ears, kitchen, dishwasher etc.

3. Normal room temperature and slightly lesser temoerature environment can be suggested. There is no oxygen deficiency in any of those niches, so that nutrient agar or broth can be easily used as media.

4. Nasal mucosa swab can have Staphylococcus aureus colonies possibly. Bathroom mat can habitat species like E.coli and streptococcus species. Refrigerator water collector swab might shows colonies of coliform bacteria as well as salmonella species. Mobile phones are habitat of a number of bacterial species like Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus aureus etc.

7. A bacterial colony can be defined as a visible clone of bacteria having similar genetic make up. All members of the colony will be identical to the original bacteria that started the colony.