title: Protection against UV disinfection of E. coli bacteria and B. subtilis spores ingested by C. elegans nematodes.
abstract: Nematodes, which occur abundantly in granular media filters of drinking water treatment plants and in distribution systems, can ingest and transport pathogenic bacteria and provide them protection against chemical disinfectants. However, protection against UV disinfection had not been investigated to date. In this study, Caenorhabditis elegans nematodes (wild-type strain N2) were allowed to feed on Escherichia coli OP50 and Bacillus subtilis spores before being exposed to 5 and 40 mJ/cm(2) UV fluences, using a collimated beam apparatus (LP, 254 nm). Sonication (15 W, 60s) was used to extract bacteria from nematode guts following UV exposure in order to assess the amount of ingested bacteria that resisted the UV treatment using a standard culture method. Bacteria located inside the gut of C. elegans were shown to benefit from a significant protection against UV. Approximately 15% of the applied UV fluence of 40 mJ/cm(2) (as typically used in WTP) was found to reach the bacteria located inside nematode guts based on the inactivation of recovered bacteria (2.7 log reduction of E. coli bacteria and 0.7 log reduction of B. subtilis spores at 40 mJ/cm(2)). To our knowledge, this study is the first demonstration of the protection effect of bacterial internalization by higher organisms against UV treatment, using the specific case of E. coli and B. subtilis spores ingested by C. elegans.
authors.affiliation: NSERC Industrial Chair on Drinking Water, Ecole Polytechnique de Montreal, Department of Civil, Geological, and Mining Engineering, P.O. Box 6079, Downtown Station, Montreal, Québec H3C 3A7, Canada. francoise.bichai@polymtl.ca
authors.forename: Françoise
authors.initials: F
authors.lastname: Bichai
authors.forename: Benoit
authors.initials: B
authors.lastname: Barbeau
authors.forename: Pierre
authors.initials: P
authors.lastname: Payment
mesh_terms: D000818:Animals; D001412:Bacillus subtilis / Q000166:cytology / Q000528:radiation effects*; D017173:Caenorhabditis elegans / Q000502:physiology* / Q000528:radiation effects; D004203:Disinfection / Q000379:methods*; D004705:Endocytosis / Q000528:radiation effects; D004926:Escherichia coli / Q000166:cytology / Q000528:radiation effects*; D005247:Feeding Behavior / Q000528:radiation effects*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D054879:Halogenation / Q000187:drug effects; D050296:Microbial Viability / Q000528:radiation effects; D013010:Sonication; D013171:Spores, Bacterial / Q000166:cytology / Q000528:radiation effects*; D013997:Time Factors; D014466:Ultraviolet Rays; D014881:Water Supply
chemical_list: D049452:Green Fluorescent Proteins