Science Buddies: "Ask an Expert"

Hello,
I am doing an experiment in which I need to collect bacteria through swabbing surfaces with a wet swab. Of course I want a liquid that is completely pure and will not have any effect on the bacteria being collected, and distilled water seems like a good option, but I heard that distilled water can actually kill bacteria. Is this true? If so, would Fiji water be a good substitute for it?
Thank you so much,
Phillipe, 9th grade.

Hi Phillipe,

These are great questions as you begin your project. I don't believe that simply touching bacteria with distilled water will kill them, but having them in distilled water for some time could kill them due to 1) osmosis causing water to enter the cells and bursting them, and 2) lack of nutrients.

That said, you are absolutely right that you don't want to collect the bacteria using any water that will affect your experiment. Off the top of my head, the biggest thing you want to be careful of is bacteria already in the water, which you wouldn't be able to distinguish from the bacteria you're collecting from various surfaces. For this reason, any water that is safe to drink could be fine (using tap water is much better for the environment than using bottled water! ), but to be sure, you should boil the water before you use it in order to kill anything that might be living in it.

I hope this helps, and good luck!

Thank you for your help!

You're very welcome!

Hello Everyone,
I am currently conducting an experiment involving killing bacteria grown in a petri dish with a bacteriophage (a bacteria killing virus) and comparing how well it kills compared to actual cleaning methods such as hand soap and five others. I am determining how well it kills bacteria by how well it can diminish bacteria colony size with surface area stickers on the underside of my petri dishes. The problem is, does bacteria immediately deompose after it dies? Would I even be able to tell if the bacteria is dead with my naked eye?
Thank you in advance, I really appreciate any answers I receive.

moderator note: I merged this post with your previous posts. Please keep your posts together on the same thread so the expert who has been helping you will see your follow-up posts. Thank you!