A Selective Medium for the Isolation of Soft Rot Coliforms from Soil

Abstract

BACTERIAL species which cause soft rot of plant tissue secrete pectic enzymes which destroy the middle lamella of the cell wall and, in vitro, liquefy pectate gel. This property has been utilized by Wieringa¹ and Stewart² in the preparation of selective media for isolating soft rotting Erwinia spp., and by Paton³ for the isolation of pectin-decomposing Pseudomonas spp. The preparation of these media involves a double-layer technique in which a calcium agar medium is overlaid with a sodium polypectate gel in which the formation of shallow pits serves as a diagnostic characteristic.