Hey, so im doing a biology EEI on finding the lowest effective concentartion of alcohol ( both isopropyl and ethanol individually) against certain bacteria. I have chosen Bacillus subtillis (gram positve) and Rhodospirrillum rubrum (gram negative). I was just wondering if anyone knew any sites on concentrations needed? Ive come across a few, some saying about 50% others saying roughly 70%. Bear in mind i am only in yr. 12, so it cant be too technichal or i will have no chance of understanding. Also i came across a lot of wiki stuff, but ive found its not too reliable so im trying my best to steer clear. Any suggestions? Please and Thankyou.

For that you have to define hat you mean with effective. For instance, you could define that killing 30% of all bacteria is a significant effect. Or go higher, or lower. If you go too low you will have trouble distinguishing effects due to alcohol from random events that may result in bacteria getting killed.

 

After that, you can start looking into concentrations that lead to those effects. For instance, for B. subtilis 70% ethanol results (if memory serves) in something close to 80% of all cells killed, around 90 something when increased to 80% ethanol, then decreasing for higher concentrations.

If you defined the level of interest as, say, 30%, the desired concentration would be most likely below 70%.

Unfortunately I do not know any resources that would give you precise numbers, however. I assume that most studies in this direction would be more interested in the high end of efficacy (i.e. killing as many as possible).

 

It would probably be easier just test it on your own.

Thanks CharonY, yeah im looking at at classing 75 to 80% of bacteria killed as effective. I will be testing it within the month, I was looking for some articles for reaerch and background information, i have done a bit of looking but nothing really what i wanted so far, i was wondering if anyone knew anything specific to the topic. Thanks again

I am certain I read papers regarding B. subtilis (must be oldish papers). For

Rhodospirillum

nothing pops to my mind. You may want to check up on sterilization recommendations, e.g. from CDC: My link.

There may updates on that, though.