Question

Microbiology Class Lab report.
Please, I need help in completing my 1st Lab report on microorganisms in the human environment. My source of the specimen: the Door handle, Refrigerator, and Telephone.

Materials and Methodis: This section should contain a list of all the materials, e glides, stains, réagents, etc. that were used to carry out your research, followed by a clear concise narrative of all procedures and techniques employed in your research. A numbered "stepwise" approach is often used to narrate. "Methods".

Question 1. Procedure for culturing microorganisms from these three sources and how to transfer it onto a nutrient agar slide.

Question   2. Preparation of a bacterial smear and gram staining.

Question 3. The procedure of inoculating plates incubated, temperature and hours.

Thank you.

Answer 1

1) Materials you would need to collect microbial samples would be : A clean cotton swab, Nutrient agar plate

i) Prepare Nutrient Agar as follows:

Composition of Nutrient Agar

• 0.5% Peptone

It is an enzymatic digest of animal protein. Peptone is the principal source of organic nitrogen for the growing bacteria.

• 0.3% beef extract/yeast extract

It is the water-soluble substances which aid in bacterial growth, such as vitamins, carbohydrates, organic nitrogen compounds and salts.

• 1.5% agar

It is the solidifying agent.

• 0.5% NaCl

The presence of sodium chloride in nutrient agar maintains a salt concentration in the medium that is similar to the cytoplasm of the microorganisms.

• Distilled water

Water is essential for the growth of and reproduction of micro-organisms and also provides the medium through which various nutrients can be transported.

• pH is adjusted to neutral (7.4) at 25 °C.

1. Suspend 28 g of nutrient agar powder in 1 litre of distilled water.

2. Heat this mixture while stirring to fully dissolve all components.

3. Autoclave the dissolved mixture at 121 degrees Celsius for 15 minutes.

4. Once the nutrient agar has been autoclaved, allow it to cool but not solidify.

5. Pour nutrient agar into each plate and leave plates on the sterile surface until the agar has solidified.

ii) Once the solid nutrient agar is ready, take a clean cotton swab and rub it on the object from which you want to collect the microbes.

iii) Carefully streak the swab over the surface of the nutrient agar plates.

iv) Keep them for incubation in dark at room temperature. You can incubate it at 37 degree celsius as well. That will give you growth of moulds and fungi, and some bacteria. Observe the plates after a few days (3-4 days)

2) Once you observe growth, prepare a bacterial smean with the desired colonies. This can be done as follows:

i) Pick up the desired colony from the nutrient agar plate carefully with a nichrome loop under sterile conditions. Take a drop of sterile saline on the slide and add the picked colony to it and gently mix with the loop.

ii) Air dry, heat fix and perform Gram's staining.

iii) Observe under oil immersion microscope at 100x

3) The plates can further be incubated at 37 degree celsius to allow growth of any slow growing organism. 1 weel period would be sufficient to allow the growth of most of the microbes. Depending on your requirement, the temperature can either be room temperature or 37 degree celsius.