Properties of Cytophaga johnsonae strains causing spoilage of fresh produce at food markets.

Two strains of gliding, orange-pigmented bacteria, isolated from fresh bell pepper and watermelon, respectively, showing soft-rot lesions, were identified as Cytophaga johnsonae. They differed from seven type strains of C. johnsonae deposited at the American Type Culture Collection (ATCC) in some properties, such as the ability to utilize glucose, xylose, trehalose, rhamnose, and sucrose. Spherical bodies resembling microcysts of Sporocytophaga sp. in addition to short rods and long filaments were observed in two strains (ATCC 29583 and 29588) throughout the growth cycle and also in aged cultures of other strains. All strains examined were shown to degrade five natural or synthetic polymers (pectin, chitin, starch, protein, and carboxymethyl cellulose). Only six strains (including ATCC 17061, 29587, 29589, and 19366) were able to infect and macerate artificially wounded potato tubers and fruits of pepper, squash, and tomato. The pathogenic strains secreted more pectate lyase in broth medium than the nonpathogenic strains. C. johnsonae, generally known as a soil saprophyte, might occasionally act as an opportunistic pathogen, causing decay of fresh produce in storage or in transit.