Do microwaves weaken or kill microorganisms?

I was just thinking about how factories zot things with radiation to make it last longer... you know, shelf-stable milk and whatnot.

Well, the average joe doesn't have (nor probably should have) access to that kind of equipment, but what about a good old microwave oven?  That's another form of non-ionizing radiation too, right?

Caveat:  I understand nobody wants to be held responsible for giving out this kind of medical advice, but in a hand-wavy, theoretical sense, does a microwave oven weaken or kill microorganisms?

On the negative side, does it diminish healthful probiotics?

On the positive side, can you do things like:
 1) Make food last longer - a lesser version of professional irradiation above
 2) Help sterilize things in a pinch (eg zap clean cloths to be used as bandages)
 3) (and this is my main reason for asking)
     help you get acclimated to local bacteria when living in a foreign country, that is, give yourself micro-doses of whatever is in the local water/raw food
     to get your immune system used to fighting off the bugs that the locals are immune to - like the live+attenuated microorganisms used in vaccines

In a nutshell, yes......a common microwave can be used for sterilizing items within reason.  One thing I've learned is that you need to have a good idea of the effective space within a microwave that is being subjected to the full effects of the radiation within the chamber.  I've microwaved many items for several minutes while a fly was buzzing around in the chamber and it flew out unscathed.  (.....don't worry, I don't make this a common practice!  ;-P )

I'm not sure how the food industry uses radiation for food preservation.  Microwave radiation from your standard oven will tend to heat samples and that would seem to be incompatible with many of the packaged food items.  

Microwave radiation will kill probiotic bacteria as well as pathogenic bacteria and likely would damage if not destroy many/most viruses.

I'm not sure I understand how you would use microwave sterilization for #3 on your list:  Why would you need sterilization for your interest in becoming acclimated to a new microbial flora regime?  Are you thinking of killing/attenuating the organisms by microwave denaturation before ingestion in hopes that your immune system will receive an initial mild reaction before full exposure to the myriad microbes in residence?  Hmmmm don't know if I've seen this approach before.

That sounds like a potentially risky thing. Radiation patterns are difficult to predict and having only partially sterilized things that are assumed to be fully sterile could cause a lot of harm.
What about a pressure cooker (and using steam)?

No, microwaves cannot affect things which are smaller than the wavelength. For example small insects such as fruit flies and ants are too small to absorb microwaves so if they're the only thing in the microwave you can turn it on and absolutely nothing happens to them. Even smaller things like bacteria and viruses are not affected at all.

Microwaves do, however, heat food. Food is generally bigger than the wavelength so it can absorb the microwaves and heats up. The heat and steam and whatnot that results does kill microbes. Since the heating is local, the rest of the microwave and possibly even the plate or bowl may not be sterilized either. Microwaves are tuned to a wavelength that's absorbed highly by water and fat, but most anything else won't get hot except indirectly.

Marc Troyka wrote:No, microwaves cannot affect things which are smaller than the wavelength. For example small insects such as fruit flies and ants are too small to absorb microwaves so if they're the only thing in the microwave you can turn it on and absolutely nothing happens to them. Even smaller things like bacteria and viruses are not affected at all.

The wavelength used in a microwave is indeed fairly long at 12cm.(4.8inches) however they can heat things smaller, microwaves work on individual molecules, any molecule with the right shape will work, water is simply the most common one. put an ice cube into your microwave it is much smaller than the wavelength of the radiation and it will still melt! try turning it on with a fly in it, you will find the fly explodes.
The only safe way to sterilise in a microwave is using steam and then you might as well just boil it.