Science Fair help please!

[watermelon83]

My boy, 12, has choosen to to do a project based on bacteria growth changes depending on growth medium and tempurature. We wil make agar dishes out of beef bullion, table sugar, corn sugar, and dme. Then innoculate the plates and store at three tempuratures (fridge(40?), room(65?), and around 80F). I'm thinking of using a brewing bacteria strain.

My questions are, which is the best strain to use for this experiment (I have no experience using any), and what is the best method for measuring the growth? He does have a 400x (maybe 600x) microscope. Also, what is the best method for controlling the amount of bacteria added to begin the culture? I'm thinking of using the method posted in the forums for storing yeast and sterilizing the loop between each dish.

Thanks in advance for any and all help.

 

[doug293cz]

If you have a homogeneous growth medium (not powder) that is gelled or very high viscosity, growth is often measured by inoculating a small spot of relatively constant size, and then measuring the diameter of the colony after a period of growth.

With the things you are looking at, making gelatin with them might work well. You would then need to include control plates with plain gelatin to use as controls.

Brew on

 

[watermelon83]

If you have a homogeneous growth medium (not powder) that is gelled or very high viscosity, growth is often measured by inoculating a small spot of relatively constant size, and then measuring the diameter of the colony after a period of growth.

With the things you are looking at, making gelatin with them might work well. You would then need to include control plates with plain gelatin to use as controls.

Brew on

Yes, thank you that's exactly what I'm looking at doing. We will make one series of plates with distilled water and agar to serve as the control. I didn't know if simply measuring the suze of the colony growth would suffice or if using a counting slide (hecto-something iirc?) would be necessary.

 

[doug293cz]

You can't count all the cells, so you would have to take several samples from each plate, and count them individually. It's likely that you will have non-uniform population density distributions, and then you have to figure out how to integrate from the samples across the entire plate. You might not want to get that complicated.

Brew on

 

[Zuljin]

We do fecals on a grid and count the colonies. I'll get our SOP tomorrow.

 

[watermelon83]

You can't count all the cells, so you would have to take several samples from each plate, and count them individually. It's likely that you will have non-uniform population density distributions, and then you have to figure out how to integrate from the samples across the entire plate. You might not want to get that complicated.

Brew on

I agree.

 

[watermelon83]

We do fecals on a grid and count the colonies. I'll get our SOP tomorrow.

I'm good with never having to deal with anything fecal thanks.

 

[doug293cz]

I'm good with never having to deal with anything fecal thanks.

Wasn't my SWMBO's favorite either.

Brew on

 

[Zuljin]

I'm good with never having to deal with anything fecal thanks.

Impossible.

Besides, fecal coloforms can ferment.

 

[doug293cz]

Well, I talked to SWMBO (a retired laboratory microbiologist), and the colony diameter thing won't work (I was confusing it with an old method of testing sensitivity of bacteria to antibiotics.) The preferred method is colony counting. First you want to create a loop for inoculating the agar plates (http://en.wikipedia.org/wiki/Inoculation_loop). It should be made of fine, stiff wire (a 0.009" to 0.011" guitar "E" string would work well.) The loop should have a diameter of about 5mm. The procedure is:

1. Flame sterilizing the loop
2. Dipping the loop in a solution of the bacteria
3. Rastering the loop back and forth across the whole surface of the agar plate
4. Incubating the plates
5. Counting the number of bacterial colonies on each plate

Brew on

 

[watermelon83]

I actually bought the plates, agar, and a loop. Each little grouping is considered a colony, correct?

 

[watermelon83]

Impossible.

Besides, fecal coloforms can ferment.

Be honest, are you making poo beer?

 

[doug293cz]

I actually bought the plates, agar, and a loop. Each little grouping is considered a colony, correct?

Correct.

Brew on

 

[Zuljin]

Damn it. I got busy and forgot, but Doug has it covered. I wonder if your choice of bacteria will stain on the plate. Our plates cause the fecals to be stained blue. We do E Coli with a UV cell card. It's cool. The E Coli glows.

I've thought about it, but waste water fecal colonies don't only "suggest" the presence of feces, it's pretty much because feces. That said, if you've swam in the wild, you've swam in "dirtier" water than our tertiary effluent, and way dirtier than our final effluent. Our end product actually improves the receiving stream.

 

[Singletrack]

Damn it. I got busy and forgot, but Doug has it covered. I wonder if your choice of bacteria will stain on the plate. Our plates cause the fecals to be stained blue. We do E Coli with a UV cell card. It's cool. The E Coli glows.

I've thought about it, but waste water fecal colonies don't only "suggest" the presence of feces, it's pretty much because feces. That said, if you've swam in the wild, you've swam in "dirtier" water than our tertiary effluent, and way dirtier than our final effluent. Our end product actually improves the receiving stream.

E. coli "suggest" the potential for fecal pathogens (as Zuljin knows). E. coli seem like the perfect organism for this project, too. They are readily available and glow under UV. And, they have that yuck factor that every 12-year old's project needs. Well, I suppose beer bacteria are cool too, but next thing you know you will have a classroom thinking we use bacteria, instead of yeast, to make beer.

Here's the SOP for obtaining E. coli. Just poop on a stick.

 

[hunter_le five]

Dookie talk. This thread took a wonderful turn.

 

[watermelon83]

E. coli "suggest" the potential for fecal pathogens (as Zuljin knows). E. coli seem like the perfect organism for this project, too. They are readily available and glow under UV. And, they have that yuck factor that every 12-year old's project needs. Well, I suppose beer bacteria are cool too, but next thing you know you will have a classroom thinking we use bacteria, instead of yeast, to make beer.

Here's the SOP for obtaining E. coli. Just poop on a stick.

It's a seventh grade Christian school science project. I know anything beer related isn't going to make it past SWMBO, let alone the teacher. My boy is.....different, in a good way, I'm not so sure playing with poo is going to be very interesting.

E.coli is a bit scary to have laying around the house no? I get that it most likely already is, but I just envision me becoming the medias doofus of the year when someone gets sick.

 

[GrogNerd]

I just envision me becoming the medias doofus of the year when someone gets sick.

never do anything stupid on a slow news day

 

[Singletrack]

It's a seventh grade Christian school science project. I know anything beer related isn't going to make it past SWMBO, let alone the teacher. My boy is.....different, in a good way, I'm not so sure playing with poo is going to be very interesting.

E.coli is a bit scary to have laying around the house no? I get that it most likely already is, but I just envision me becoming the medias doofus of the year when someone gets sick.

You can buy the stuff if you think your poop contains some pathogens. For example: http://www.carolina.com/bacteria/escherichia-coli-living-k-12-strain-tube/155068.pr

I know my poop is not only pathogen-free, but it doesn't stink either.

 

[watermelon83]

Thanks Z! Turned my honest question into another s*** thread.... lol

 

[GrogNerd]

never do anything stupid on a slow news day

I hate to repeat myself, but...

never do anything stupid on a slow news day