Method of reducing the number of microorganisms in a media and a method of preservation

A method of reducing the number of viable bacteria, fungi, algae and yeast in media by physically contacting the bacteria, fungi, algae and yeast with a surface which has been altered in a manner which comprises contacting a substrate, which develops a negative charge in water, with an amount effective to inhibit the growth of said microorganisms of a substance that ionizes in water to form cations and anions which substance is selected from the group consisting of sulfonium salts of the formula R.sup.8 R.sup.9 R.sup.10 S.sup.+ X.sup.-, sulfonium salts of the formula ##STR6## isothiuronium salts of the formula RSC(NH.sub.2).sub.2.sup.+ X.sup.-, isothiuronium salts of the formula ##STR7## phosphonium salts of the formula R.sup.4 R.sup.5 R.sup.6 R.sup.7 P.sup.+ X.sup.-, and phosphonium salts of the formula ##STR8## wherein R.sup.8, R.sup.9 and R.sup.10 are independently alkyl groups or aralkyl groups wherein there is a total of less than 30 carbon atoms in the molecule or a silylsubstituted alkyl radical of the formula ##STR9## where Y is a hydrolyzable group, Q is an alkyl radical of 1 or 2 carbon atoms or (CH.sub.3).sub.3 SiO, a has an average value of 0-3, b has an average value of 0-3, n is an integer of 1 or greater and X.sup.- is a water soluble monovalent anion, R is independently alkyl or aralkyl groups wherein there is a total of less than 20 carbon atoms in the molecule or a silylsubstituted alkyl radical of the formula ##STR10## as defined above, R.sup.4, R.sup.5, R.sup.6 and R.sup.7 are as defined above for R.sup.8, R.sup.9 and R.sup.10 ;

• R.sup.11 and R.sup.12 are independently alkyl groups or aralkyl groups wherein there is a total of less than 60 carbon atoms in the molecule and d is an integer of 1 or greater.