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How does the cladoceran Daphnia pulex affect the fate of Escherichia coli in water?

Jean-Baptiste Burnet, Tarek Faraj, Henry-Michel Cauchie, Célia Joaquim-Justo, Pierre Servais, Michèle Prévost and Sarah Dorner

Article (2017)

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Cite this document: Burnet, J.-B., Faraj, T., Cauchie, H.-M., Joaquim-Justo, C., Servais, P., Prévost, M. & Dorner, S. (2017). How does the cladoceran Daphnia pulex affect the fate of Escherichia coli in water? PLoS ONE, 12(2), p. 1-16. doi:10.1371/journal.pone.0171705
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Abstract

The faecal indicator Escherichia coli plays a central role in water quality assessment and monitoring. It is therefore essential to understand its fate under various environmental constraints such as predation by bacterivorous zooplankton. Whereas most studies have examined how protozooplankton communities (heterotrophic nanoflagellates and ciliates) affect the fate of E. coli in water, the capacity of metazooplankton to control the faecal indicator remains poorly understood. In this study, we investigated how the common filter-feeding cladoceran, Daphnia pulex, affects the fate of E. coli under different experimental conditions. Daphnia ingested E. coli and increased its loss rates in water, but the latter rates decreased from 1.65 d(-1) to 0.62 d(-1) after a 1,000-fold reduction in E. coli initial concentrations, due to lower probability of encounter between Daphnia and E. coli. The combined use of culture and PMA qPCR (viability-qPCR) demonstrated that exposure to Daphnia did not result into the formation of viable but non-culturable E. coli cells. In lake water, a significant part of E. coli population loss was associated with matrix-related factors, most likely due to predation by other bacterivorous biota and/or bacterial competition. However, when exposing E. coli to a D. pulex gradient (from 0 to 65 ind. L-1), we observed an increasing impact of Daphnia on E. coli loss rates, which reached 0.47 d(-1) in presence of 65 ind. L-1. Our results suggest that the filter-feeder can exert a non-negligible predation pressure on E. coli, especially during seasonal Daphnia population peaks. Similar trials using other Daphnia species as well as stressed E. coli cells will increase our knowledge on the capacity of this widespread zooplankter to control E. coli in freshwater resources. Based on our results, we strongly advocate the use of natural matrices to study these biotic interactions in order to avoid overestimation of Daphnia impact.

Uncontrolled Keywords

Animal Feed; Animals; Daphnia; Environmental Monitoring; Escherichia coli; Lakes; Microbial Viability; Water; Water Microbiology; Water

Open Access document in PolyPublie
Subjects: 1000 Génie civil > 1000 Génie civil
1500 Génie de l'environnement > 1500 Génie de l'environnement
1500 Génie de l'environnement > 1501 Qualité de l'eau, pollution
Department: Département des génies civil, géologique et des mines
Research Center: Autre
Funders: National Research Fund, Luxembourg and co-funded under the Marie Curie Actions of the European Commission, CRSNG, Canada Research Chair (CRC) in Source Water Protection
Grant number: FP7-COFUND
Date Deposited: 14 Dec 2018 16:17
Last Modified: 15 Dec 2018 01:20
PolyPublie URL: https://publications.polymtl.ca/3537/
Document issued by the official publisher
Journal Title: PLoS ONE (vol. 12, no. 2)
Publisher: PLOS
Official URL: https://doi.org/10.1371/journal.pone.0171705

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