Freezing is lowering the temperature below zero Celsius. In anything made of water, the procedure creates ice crystals that poke the cell membrane, making a lot of microscopic holes than quickly leach the inner contents of the organism by differences in osmotic pressure. This kills the cell by "bleeding to death".
As bacterias are cells with membranes in principle they are killed when frozen, so far, so good...
... but this is just the general case. Not all bacterias have being created equal and there are thousands of species.
Some are extremophiles and store sugar or other substances that act as an antifreeze, so can decrease the temperature of freezing and remain "liquid" under zero point. They can stand much lower temperatures before being killed (by freezing). Is just that they are killed at -25C instead -5C, but the killer is still a tiny ice dagger.
And some bacteria have evolved an outer protective gelatinous capsule, made partially with "sugar", that is not easy to pierce, so they can alter their osmotic pressure and stand more osmotic stress.
And finally, some will just die, but not before creating a inner spore devoid of water that can stand the cold or dry until rehydrated. No water, no ice.
Sushi. Never eat "fresh" sushi. The reality is that fish destined for or sushi, other that tuna, is always hard frozen for a considerable period of time to destroy not just bacteria but a whole variety of parasites. It does work. Do not fall into the belief that freezing is not effective. Freezing is a common part of health codes for good reason. (It is also why I personally stay away from some forms of "fresh" fish.)
"Parasite Destruction for Raw Fish: Seafood products to be served raw must: Have been frozen at a temperature of –20°C (-4°F) for 7 days or below –35°C (-31°F) for 15 hours, to destroy parasites that might be present."
But then if you go to Tsukiji fish market in Japan they will serve you fresh seafood raw and this happens probably hundreds of thousands of times a year.
Just for context, neither of two of the most common food borne bacteria (E. Coli O157:H7 and Salmonella) are killed by typical freezer or refrigerator temperatures.
The current brains are totally lost. Maybe a partial image of memories could be recovered when we understand more about the process but I wouldn't count with it.
But if tomorrow we would found a suitable antifreeze in some obscure creature that is not rejected by the body and does not damage the cells, this is a game changer. To be able to put the body just about to freeze but not further... that would be awesome.
Would be a key to 1-hibernation and long term space travel, 2-increase life expectancy slowing the metabolism and this mean slowing cancer also, 3-increase in the range of temperatures that humans can stand without suffering chill burning and losing fingers.
De-thawing would be still a brutal process. Not all cells would survive.
Well, I doubt the revival process too but the freezing bit might be ok if it was done expertly well.
My understanding was that ice crystal length was also related to time taken to freeze.
IE freezing faster produced smaller crystals that don't then damage the cells so much.
We have a liquid nitrogen icecream shop that exploits the shorter crystal length to make "creamier" icecream while you wait. Not exactly how I'd want my brain frozen but hopefully the cryogenic experts know a way.
That sounded really expensive but apparently it can be as cheap as $0.50/gal, and about 1 gallon of liquid nitrogen will freeze 1 gallon of liquid cream, and 1 gallon of premium ice cream has maybe $5 worth of ingredients, so I suppose it would probably work out plus or minus an order of magnitude. Neato!
Yeah, liquid nitrogen is not that expensive despite how exotic it sounds.
But it really does need to be handled appropriately. For example, while you can put it in a simple thermos flask you shouldn't be in small enclosed spaces with it. IE elevator/car.
The liquid expands to quite a lot of gas and might force out all the standard air taking the oxygen with it.
But mainly it is about 'freeze burns'.
My wife(science lab manager) cringes at the lack of safety glasses and gloves at the ice cream shop.
They plonk ingredients into an open top mixer/blender and then pour the liquid nitrogen in while it is running!
Thanks for the correction. I borrowed the spanish plural.
Trivia: Spanish would distinguish between "una bacteria" (one bacterium) feminine noun in Spanish so it ends in "a", and between "una colonia de bacterias" (a colony of bacteria). Bacterias would be the correct plural in Spanish. English works a little different here.
English still prefers using the Latin and Greek plurals for words borrowed from, or indeed inherited from, Latin and Greek. "medium"/"media", "datum"/"data", "stratum"/"strata", "stigma"/"stigmata", "bacterium"/"bacteria", "schema"/"schemata" ...
The exceptions are things like
* mixed modern coinages (e.g. "television", a Latin suffix with a Greek prefix),
* divergent modern coinages ("bicycle" is not Greek "κύκλος" nor Latin "cyclus", and was taken from French),
* words not attested in the plural in the original language (e.g. "virus", only attested in the singular),
* words not actually singular in the original language (e.g. "ignoramus" is a verb in Latin, first person plural), and
* things that have since diverged (e.g. "hippopotamus", where "ποταμός" meaning "river" is "-ός" and hence "ποταμοι" in Greek but the word that English has came via Late Latin).
English generally pluralizes these things the Germanic way with "-es"/"-s", although pluralizing "hippopotami" as Latin is well attested and "bicycles" is the French plural.
Getting English speakers to remember "spaghetto", "panino", "confetto", "graffito", "paparazzo", or even "die" (singular of "dice") is somewhat hard. (-:
https://ask.usda.gov/s/article/Does-freezing-food-kill-bacte...