how do you know the gas that is created by your bacterium is the reason e.coli dies
By using negative controls, one without any second bacteria and one with a non-antagonistic bacteria.
How are you going to put e.coli on that paper and keep it alive?
From a liquid culture with a known OD600. It will stay alive for the time the experiment lasts.
You are going to try to put each colony above a well then?
Yes, one blotting paper for each multi-well plate and an exact amount of E. coli culture above each well.
I think that everything would work fine, except of a quick live/dead analysis. Maybe a wipe test would work after the incubation time...
I still couldn't find any reagent for an easier determination of living/dead cells.
Yeah, well that last phrase summs it up: I see what you want to do, but how are you going to test it (dead vs alive)?
Putting the bacteria on a piece of paper... its not an easy method.
An idea or solution, could be to plate every "colony" from the blotting paper on a new petri dish to see if its still alive or not....(I think this is what you mean with the wipe test?)
But however you turn it, you well have lots and lots of work.
BTW: did you test it ? Did E.coli grow good enough on the paper? Did it really enter exponential growth on the paper? If it doesnt: then you can test for it to be alive or not, but the information you get out of that doesnt mean a lot. (well it depends on the negative strain).
+the negative control: how long are you going to run the experiment?
Anyway: I think you can try this, but in the end you will need to do more accurate tests with the strains that seem to kill E.coli.
My idea would have been a bit different and a lot more work, so I guess yours is better altough, the idea of using paper with bacteria on it... eum... I also wonder: how many samples are you going to take for each strain? You cant just blot one.. So how many did you think on doing?
If I was you: I would now start with the negative control! Check what you get if you put e.coli on a piece of paper above a multiwell filled with medium.
See of the medium has growth : e.coli falling in it?
See of the e.coli on the paper is still alive (plate it out)
If you start with this, then you allready know if this is an option or not.
Also: check the growth of e.coli at different time-intervals.
If you don't know it, then ask it! Better to ask and look foolish to some then not ask and stay stupid.