Science Buddies: "Ask an Expert"

I was wondering if anyone knew how to gain access to a laboratory that would allow middle school students to grow cultures of bacteria. My project is to test the impact of starvation on future generations of bacteria. Does anyone know how to find laboratories that are open to students, and if so, how to obtain access to them?

Thank you.

Hi Rakesh,

If you live in an area where there is a university you could go to their website and then find the websites for the departments that might be doing bacterial work--the department of microbiology or molecular biology. Find the list of the faculty in the department and if they have a website you can read about the kind of research they do and whether it involves bacterial culture. Many university labs that do mammalian cell culture also do bacterial work.

You can, of course, culture the nonpathogenic K12 strain of Escherichia coli at home and then you would not have to find a lab and a mentor. You said you wanted to test the effects of starvation on bacterial growth. Why do you want to do that? What is your hypothesis? Which bacteria would you use? We may be able to help you better if you would explain your project more.

A university lab is a busy, high pressure place and technicians, graduate students and post-docs don't have much time to supervise a middle school student who knows little about working in a professional lab. We used to have a couple of high school students in our lab over the summer but they had to work there every day for 12 weeks to accomplish a meaningful project and someone had to be helping them all the time. You can find a mentor and a lab to work in but you have to have thought up a good, workable project that asks an interesting question that is related to the research focus of the lab, and you have to demonstrate that you know your subject very well and can make a major commitment of time to accomplish the project.

Culturing bacteria, plating them on agar in Petri dishes and doing cell counts can be done at home or in a basic school science lab. Did you read about working with bacteria in the various Scibuddies projects? This will give you a good idea what you can do with a small budget. Youtube has a large number of tutorial videos on growing, counting, plating and working with bacteria and you can learn a lot by watching an experienced lab worker going through the procedures. You will see how it is done and you will see what kinds of equipments and supplies you need. It really is quite basic science, but you can do interesting and important projects with a little background reading and imagination.

Think about what you want to do and post a more detailed outline of your project so we can help you better.

Good luck!

Sybee

Thank you for responding Sybee,

The reason I would like to study how bacterial colonies grow when they are starved is because I think that it is important to understand how bacteria respond to different conditions. Bacteria have caused multitudes of lethal infections, which have been treated by antibiotics. I wondered if bacteria could be combated by starving them, without the bacteria developing resistance that is passed on to future generations. My hypothesis is that bacteria will adapt to starvation by developing a higher metabolism, a trait which will be passed on to future generations.

I am not sure which bacteria to use. Are there certain types of bacteria that are more suitable for this type of project? If not, I would use E. coli.

I will try to find local universities, as well as a mentor and a lab. If that doesn't work, I will culture the K12 strand of E. coli at home and observe how the colony responds.

Thank you

Hi Rakesh,

I think your idea of starving would work in the test tube but not in humans--at least not without serious side effects. When a person has a bacterial infection, the bugs use the nutrients in the body--glucose and proteins in the blood or tissues. It would be difficult to starve them without doing serious injury to the person suffering the infection.

You are on the right track from a genetic standpoint, however, because attacking a bacterium through its metabolism might be a way to kill it without its being able to become resistant. Like humans, bacteria have digestive enzymes and metabolic pathways for using food. Rather than trying to deprive the bugs of food, which would probably also kill the infected person, you could try to find a drug that blocks something in the metabolic pathway. This would starve the bacteria from the inside out. The food would still be present, but they couldn't use it.

OK. That sounds like a great idea, but how do you make a project out of it? You can use E coli K12 as your test organism, but what would you test? How would you find out what compounds would block bacterial metabolism without harming a person? You don't have access to a shelf full of exotic chemicals to try, but you could use a variety of herbal compounds that have been shown to have antibacterial properties. Maybe there are some herbs that are thought to work by blocking bacterial metabolism. You'll have to do some research on Google Scholar and see what you can find.

I hope this gives you some ideas about how to proceed. Let us know what you want to do and we'll try to guide you in developing a good hypothesis and the experiments to test it.

Good luck!

Sybee

Hi Sybee,

If I can find a successful way to block metabolism in a bacteria, I would robably do it in the test tube because I don't think the science fair I am participating in allows me to do it in humans. Like you said, I will have to do some background research on what type of compounds can block the metabolic pathway in bacteria.

I would like to test how bacteria respond to starvation, or to compounds that block their metabolism. Also, I would vary the amount of time bacteria's metabolism is blocked to observe which time best impairs the bacteria's ability to digest.

The dependent variable that I would test would be colony size. If the bacteria's metabolism is impaired, bacteria will probably have more difficulty reproducing, which decreases colony size. My control would be a bacteria who is left alone and functions normally. My hypothesis is that the bacteria whose metabolism is blocked for the longest amount of time will have the lowest colony size.

Thank you
Rakesh

Hi Rakesh,

I'm not sure if measuring colony size is the best way to quantitate a drug's effect on bacteria. Do some more reading on this. In my opinion, an antibacterial needs to completely block bacterial growth, so what you would compare would be the number of colonies with and without treatment.

Another way to do this would be to buy or build a device to measure the turbidity of a bacterial culture. As bacteria grow and divide in liquid medium, the turbidity of the liquid increases and this can be measured as a reduction in the intensity of a light that is shined through the culture in a test tube. The light intensity is measured electronically by a photocell. Building a device (called a turbidimeter or nephelometer) to do this is not that difficult if you are handy with electronics and building gadgets. Here's one example of such a device: https://www.sciencebuddies.org/science- ... p032.shtml

Using a nephelometer is a simple way to measure effects on bacterial growth because you don't have to make dilutions, plate the bacteria on agar and count colonies. You can see your results in a few hours and tweak the drug concentrations if necessary.

Good luck exploring this topic and post here again when you have more questions.

Sybee