Bacteria Friend Foe

Title (make it specific to your experimental question)


In one paragraph include the following:

  • Provide at least three pieces of background information about bacteria. This information should be relevant to your hypothesis. Cite outside sources!
  • Explicitly state the hypothesis andprediction of your microbiology experiment.
  • Use one or two sentences to connect your background information with the importance of your hypothesis and your prediction for the experiment.

Materials and Methods

  • Include table showing how you set up your experiment
  • In a few sentences describe how sampling was done and the conditions of incubation

Results (you need figures, tables AND text)

  • Include the total number of colonies, and total number of different types of colonies that grew on each of the agar plates if possible. Distinguish between growth on nutrient agar, blood agar and agar + tetracycline. Organize your data into tables!!!
  • Include descriptions comparing your experimental plates to the control plates
  • Include descriptions and conclusions about the type of hemolysis you observed on the blood agar plates.
  • Include drawings or pictures of agar plates (including control plates)
  • Describe what the bacterial growth looked like on each of the plates in general terms and in paragraph form
  • Refer to your drawings, figures and tables in your results text.


  • In 2-3 sentences, summarize the purpose of the experiment based on background information that you researched.
  • Describe how the results supported or refuted your hypothesis and prediction. Refer to data from the results to do this. You may also need to explain why results were inconclusive. (1-2 paragraphs).
  • Describe any problems with observing and quantifying the bacteria colony growth on the different plates.
  • How do you think the properties of the food you tested affected this experiment? What other factors affected the results of this experiment? If you could repeat your experiment, what would you change or improve? (three sentences total)
  • Different species of bacteria have growth requirements that are specific to their needs. Their needs vary greatly because bacteria grow everywhere from the hot springs of Yellowstone to the Antarctic. Based on this idea, do you think the same types of bacteria grew on the nutrient agar as the blood or tetracycline  agar? Why or why not? Do you have any proof of this from your experiment? Explain in a few sentences.
  • In a couple of sentences, write a conclusion about you experiment and what you learned.

References: Minimum of 3. Cite them in the text, using APA format.



Bacteria are one of the prokaryotic microorganisms; they are a few micrometers in length, having a number of shapes, ranging from spheres to rods and spirals. There are many ways to classify bacteria based on their staining, favored media of growth and oxygen requirements (Wilson & Miles, 1975).  These microorganisms are found everywhere, some live in our bodies as part of normal flora, others in the air, water, food, decaying matter and sewages etc. Some bacteria such as cholera are very harmful and cause serious diseases while others are relatively harmless especially those that form part of normal flora such as Rothia species.

Bacteria can be isolated from their natural reservoir, cultured using various culture media and more studies done on them (Brock, T. D. 1988). Antibiotics, which are used to treat bacterial infections, are also tested against their sensitivities to various bacteria in the lab using a sensitivity chart in various bacteria cultures. This experiment was therefore on study of various bacteria types through isolation, culture and sensitivity against antibiotics like tetracycline.


The hypothesis in this experiment was there is more bacteria found on the floor compared to the table and the longer food in contact with an infected surface the higher the number of bacteria it attracts. The five-second rule was applied in this hypothesis.



  1. Bologna food
  2. Agar plates
  3. Culture nutrient materials i.e. nutrient agar, blood agar and nutrient combined with tetracycline antibiotic.
  4. Surfaces- table and floor


Bologna food was divided into two, one was dropped on the floor and the other on the table for 10 seconds. It was then picked and swapped to 3 agar plates each divided into halves. One contained nutrient, the other blood and third one had nutrient combined with tetracycline.  There was an empty control agar plate. We waited for a week to see the results.

Plate Agar Type Food type Surface Time
First half Nutrient Bologna Table 10 seconds
Second half Nutrient Bologna Floor 10 seconds
First half +Tetracycline Bologna Table 10 seconds
Second half +Tetracycline Bologna Floor 10 seconds
First half Blood Bologna Table 10 seconds
Second half Blood Bologna Floor 10 seconds
Control(TA) Nutrient Gummy bear bologna N/A N/A
Control(TA) +Tetracycline Gummy bear bologna N/A NA
TA Blood Gummy bear bologna N/A N/A


Results collected are summarized in the table above and the picture of the three different colonies.

Plate Agar Type Total # of Colonies # of colonies based on morphology Any additional results
1.First half Nutrient 89 (Table) 4
1.Second half Nutrient 88 (Floor) 4
2.First half +Tetracycline 140 (Table) 3
2.Second half +Tetracycline 16 (Floor) 2
3.First half Blood 40 (Table) 5 Beta, Gamma & Alpha
3.Second half Blood 62 (Floor) 3 Beta and Alpha
4.Control(TA) Nutrient 12 1
5.Control(TA) +Tetracycline 3 1
6.TA Blood 11 1 Beta

The colonies grown on the agar plates are as below

Nutrient  +Tetracycline agar                               Blood Agar                             Nutrient agar

As seen from the pictures of these agar plates the nutrient agar had an almost similar number of colonies. The list number of colonies was found in the tetracycline agar. Alpha, beta and Gamma hemolytic reactions were observed in the blood agar. Tetracycline had an inhibitory  effect on bacteria growth. There is no much difference in number of bacteria colonies found on the floor and table.


From this experiment there is no much difference between the number of bacteria’s found on a table and the floor. The type of bacteria is however different as demonstrated after observing using a microscope.

These results refuted the hypothesis. There was a general assumption that more bacteria colonies would be found on the floor as compared to the table. The size of sample in this experiment might however, be inadequate to come up with a conclusion. A lot of precision was observed in this experiment and I would stick with the finding that there is equal number of bacteria on the floor and the table.

The biggest challenge was observing and counting the number of bacteria in each agar. Using a microscope needed a lot of skills and it took quite long. There may have incidences of double counting. Isolation of colony types was easy as it was very clear to distinguish the types.

Different types of results might have been obtained if a different food type was used. There might be certain properties in a food type that may favour or hinder a bacteria growth. Bacteria’s have a preferred growth media. The highest number of bacteria grew in a nutrient agar as compared to the other two. However the first half of the tetracycline agar had a lot of bacteria, this is against general knowledge since antibiotics hinder bacteria growth. There could have been some sort of resistance by the bacteria from the table to tetracycline. The second half had the least number of bacteria and therefore showing there are different bacteria types on the floor and table since the response was different.


Bacteria are found on all surfaces. The can be isolated and grown in different agars. Bacteria’s grow differently in various agar types and this can be used to distinguish them. Efficiency of an antibiotic against a certain bacteria can be tested by including it in the agar or culture media