▁is ▁a ▁non - equ ilib rium ▁process , ▁it ▁does ▁not ▁qual ify ▁as ▁free zing , ▁which ▁requires ▁an ▁equilibrium ▁between ▁the ▁cry st all ine ▁and ▁liquid ▁state . ▁ ▁Exp ansion ▁Some ▁subst ances , ▁such ▁as ▁water ▁and ▁b ism uth , ▁expand ▁when ▁fro zen . ▁ ▁Free zing ▁of ▁living ▁organ isms ▁ ▁Many ▁living ▁organ isms ▁are ▁able ▁to ▁toler ate ▁prolong ed ▁periods ▁of ▁time ▁at ▁temper atures ▁below ▁the ▁free zing ▁point ▁of ▁water . ▁ ▁Most ▁living ▁organ isms ▁accum ulate ▁cry op rote ct ants ▁such ▁as ▁anti - n uc le ating ▁prote ins , ▁poly ols , ▁and ▁gl uc ose ▁to ▁protect ▁themselves ▁against ▁fro st ▁damage ▁by ▁sharp ▁ice ▁cry st als . ▁Most ▁plants , ▁in ▁particular , ▁can ▁safely ▁reach ▁temper atures ▁of ▁− 4   ° C ▁to ▁− 1 2   ° C . ▁C ertain ▁b acter ia , ▁not ably ▁Pseud omon as ▁s yr ing ae , ▁produce ▁special ized ▁prote ins ▁that ▁serve ▁as ▁pot ent ▁ice ▁nucle ators , ▁which ▁they ▁use ▁to ▁force ▁ice ▁formation ▁on ▁the ▁surface ▁of ▁various ▁f ruits ▁and ▁plants ▁at ▁about ▁− 2   ° C . ▁The ▁free zing ▁causes ▁inj uries ▁in ▁the ▁ep ith elia ▁and ▁makes ▁the ▁nut ri ents ▁in ▁the ▁underlying ▁plant ▁t issues ▁available ▁to ▁the ▁b acter ia . ▁ ▁B acter ia ▁Three ▁species ▁of ▁b acter ia , ▁Car n ob acter