How can you be sure that the turbidity produced in the broth tubes was caused by the bacteria used for the inoculation?

Answer 1

You can't tell from looking. you'll have to streak a plate and look at the colonies formed and their morphology. If all the colonies look the same, chance favors a pure culture. However, you could do a few stains from the broth to examine if the microbes look different

Gram Stain comes to mind immediately because you don't need to have a pure culture to get good results.

Answer 2

i don't exactly know the experiment but if you want i can make a guess:

You can tell because you keep all other veriables the same so only your independent variable changes.

And also perform a control experiment exactly the same but without the bacteria, this gives no result, which proves it was the bacteria that did it.

Answer 3

It is nearly impossible to identify if you had a pure culture or a mixed culture. If you were using fluid thio as a medium, perhaps you might be able to see where the growths are. If there are growths near the top, and near the bottom, you can safely assume your sample was a mixed culture.

Answer 4

- Get a sample,

- Created dilutions that are in range of expectation. 10^9, 10^10, etc.

- Put the dilutions on plate

- Put in stove overnight

- Next morning look at the plates, find the one with countable/separated colonies.

- Count he number of colonies.

- Using the dilution and amount of dilution put on plate you can calculate the concentration/amount of microorganisms in the broth tube. Which should still be around accurate if you put the broth tube in the refrigerator overnight.

Answer 5

Cheap: strike it out on steril Agar (use different dilutions to get a nice result) and incubate. After several hours you can see various colonies growing - determine by the look at it if they resemble each other or if they look different.

Expensive: run genome anaylsis