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Tryptophan like and humiclike fuorophores are extracellular in groundwater: implications as real time faecal indicators

Fluorescent natural organic matter at tryptophan like (TLF) and humic like fuorescence (HLF) peaks is associated with the presence and enumeration of faecal indicator bacteria in groundwater. We hypothesise, however, that it is predominantly extracellular material that fuoresces at these wavelengths, not bacterial cells. We quantifed total (unfltered) and extracellular (fltered at < 0.22 µm) TLF and HLF in 140 groundwater sources across a range of urban population densities in Kenya, Malawi, Senegal, and Uganda. Where changes in fuorescence occurred following fltration they were correlated with potential controlling variables. A signifcant reduction in TLF following fltration (?TLF) was observed across the entire dataset, although the majority of the signal remained and thus considered extracellular (median 96.9%). ?TLF was only signifcant in more urbanised study areas where TLF was greatest. Beneath Dakar, Senegal, ?TLF was signifcantly correlated to total bacterial cells (?s 0.51). No signifcant change in HLF following fltration across all data indicates these fuorophores are extracellular. Our results suggest that TLF and HLF are more mobile than faecal indicator bacteria and larger pathogens in groundwater, as the predominantly extracellular fuorophores are less prone to straining. Consequently, TLF/HLF are more precautionary indicators of microbial risks than faecal indicator bacteria in groundwater?derived drinking water.

Auteur(s) : James P. R. Sorensen, Andrew F. Carr, Jacintha Nayebare, Djim M. L. Diongue, Abdoulaye Pouye, Raphaëlle Rofo, Gloria Gwengweya, Jade S. T. Ward , Japh
Pages : 9 Pages
Année de publication : 2020
Revue : Nature Scientific report
N° de volume : (2020) 10:15379
Type : Article
Mise en ligne par : CISSE Seynabou