Escherichia coli O157:H7 attachment and persistence within root biofilm of common treatment wetlands plants

Pathogen retention and subsequent release within the rhizosphere of wastewater treatment wetlands may be a concern for human health. To address this concern, the enteric pathogen Escherichia coli O157:H7 with a DsRed plasmid insertion was used as a model pathogenic organism in an open-air chemostat reactor with constant flow of simulated wastewater. Colonization and persistence of the organism was tracked on roots of two obligate wetland plant species, Carex utriculata and Schoenoplectus acutus, originally grown in pilot scale wetland reactors. Teflon nylon string, clean and with existing indigenous biofilm, was used as an inert surface control. Epifluorescence microscopy and qPCR were used to verify E. coli O157:H7 abundance for up to 1 week. Initial attachment was seen on all surfaces, with colonization decreasing through 1 week. qPCR showed preferential association of the pathogen with roots over the nylon. There was a significant difference between plant type; S. acutus showed significantly higher numbers compared to C. utriculata. E. coli O157:H7 binding and persistence on root surfaces may be a means of survival in treatment wetlands.