[Modified method for determining water pollution by using a Serratia marcescens culture]

The method for determining the degree of water pollution with the aid of a bacterial tracer has been improved by using: (1) a technique for maintaining the culture of Serratia marcescens; (2) a medium whose composition provided for a high level of prodigiosin in the bacterial culture; and (3) an express method for assaying the degree of pigmentation during growth of Ser. marcescens on solid media.