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Biology/Last Minute Bio Project


QUESTION: I am doing a science project that is mandantory and I have been extremely busy for the past month with personal business regarding family. I am also taking extremely hard classes including AP human geography, Honors English 10 and Honors Biology. So I haven't looked at my expirament with much thought and I am working to the last minute. I have three days left. My expirament is how different kinds of sugars mixed with water effect the growth of bacterial cultures. I used nutrient agar and the different sugars. I placed the petri dishes upside down in a dark box placed in a room heated at 75 degrees f. I am not seeing any results and I am worried. It has been 2 days and I need quick results. My next question is how can I get tangible data? I don't have and can't afford anything fancy and I really don't have alot of time. I understand If you can't help me out but If you have advice it would be greatly appreciated. Thank you!

ANSWER: Hi Kaitlyn
You have left out some information here that I would need to know about your experimental design. How are you exposing your plates to bacteria. To get maximum growth I would suggest a t swab of the skin or surface area. Computer keyboards and loaded with bacteria These  bacteria will grow on nutrient agar. Before you streak the plates you can add a small amounts of sugar solutions. and spread it over the surface  Also I think you should place the plates right side up under a goose neck lamp.or other heat lamp giving heat near 37.5 degrees C.   Bacteria will grow within 24 hours at close to body temperature. Be sure you use a control plate using plain water.
Since you do not the ability to identify the cultures you will have conduct a quantitative study and not a qualitative one. This would involve comparing the amount of growth on the sugar plates with the control plate counting the number of colonies
 I also do not your instructors requirements are but the scientific method needs a Problam statement and a hypothesis. Have you stated these
 I will be interested if your results so keep me informed

---------- FOLLOW-UP ----------

QUESTION: Okay so I used a cheek swab sample using a sterile swab and I wiped it in a motion like a dollar sign just with out the line through it. I did this wrong I believe because I misunderstood a sight I read and I used absorbant paper to soak up the sugar. I have very little time so I do not think I can redo any of this.

If you cut little circles of the paper and put them on thr dish taht should work as it will tell you if growth as inhibited. Discs are used to test antibiotics affects on growth.  Try incubating the plates again under a heated light. but keep at around body temperature
 You should get a lot of harmless strep cells from the mouth


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Walter Hintz


Science teacher for over 50 years. MSc. in biology. I can answer questions in general biology, zoology, botany, anatomy and physiology and biochemistry.


I have a MSc in biology and have been a science teacher for over 50 years. At present I am a faculty member at a college and a science consultant at seven catholic schools.

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