ABSTRACT
Saprophytic Microorganisms The microbial species that prevail on fruits and vegetables are commonly found on plants in the field or after harvest, and probably originated from the epiphytic microflora of the raw materials. Pseudomonas fluorescens, Erwinia herbicola, and E. agglomerans are major components of the epiphytic microflora of many vegetables (Khan et al., 1992; Senter et al., 1987). An average Leuconostoc spp. population of 2.5 x IO4 CFU (colony forming units).g1 was found on plants by Mundt et a l.(1967), although other studies indicate lower frequencies (Lin et al., 1992) (1 to 33% in various crops). Yeast species have been identified from raw fruits and vegetables (Deak, 1991; Magnusson et al., 1990). Similarly, pectinolytic Pfluorescens, pectinolytic spp., Cytophaga spp., and Flavobacterium spp. have been isolated from various unprocessed vegetables sampled in retail outlets (Liao and Wells, 1987a,b). More generally, pectinolytic fluorescent pseudomonads are well known agents causing soft rot diseases of leafy vegetables (Brocklehurst and Lund, 1981; Ohata et al., 1979; Sellwood et al., 1981; Vantomme et al., 1989) and can account for an important fraction of epiphytic microflora: IO4 pectinolytic Pseudomonas cells cm 2 on white cabbage leaves (Geeson, 1979). Counts as high as 109 CFU.g1 have been noted in fresh soil (Cuppels and Kelman, 1974), although lower values have also been reported (Sands and Hankin, 1975). The presence of pseudomonads on vegetables presumably does not depend on external contamination, as they are probably endemic.
