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Microbiome of drinking water: A full-scale spatio-temporal study to monitor water quality in the Paris distribution system.

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PubMed ID: 30471533

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Perrin Y, Bouchon D, Delafont V, Moulin L, Héchard Y

Water Res. Feb 2019

COMMENT: This study used high-throughput sequencing (HTS) to analyze the microbiome of a large drinking water distribution system over a one-year period of time, the HTS-based method was compared with a culture-based method. The paper shows the sensitivity and usefulness of HTS tools in assessing of microbial water quality.

Objective:

The study aimed to perform high-throughput sequencing of the 16S rRNA gene (V3-V4 region) to characterize bacterial communities of the Paris’ drinking water distribution system (DWDS) over a one-year period and to compare microbial variation with the data provided by heterotrophic plate count (HPC). The main objective was to understand the factors that could influence the microbiome of a large water network through time and space, such as the origin of water, temporality and the selected physico-chemical parameters.

Main results

In total, 1321 taxa were identified in four DWDSs of Paris, but bacterial communities were dominated by 15 different taxa.

There was a clear domination of the Rhizobiales order (Alphaproteobacteria), with the two genera Hyphomicrobium and Phreatobacter.

Bacterial diversity and composition are similar between the four DWDS of Paris.

Our results showed a moderate impact with an increase of bacterial diversity during summer and autumn, but without changes in the community structure.

The following highly abundant taxa showed significant variations along the year. Relative abundance of Phreatobacter, Maricaulis and Mycobacterium genera was significantly higher during warm period (June 2016 to October 2016; corresponding to a water temperature >15º C) than during cold period (March 2016 to May 2016 and November 2016 to February 2017; water temperature <15º C), in the four DWDS.

Conversely, Hyphomicrobium and Pseudomonas abundances were significantly higher during cold period than in warm period.

Bacterial community composition is poorly explained by the physico-chemical parameters.

About the comparisson of a culture-dependent method with the HTS-based characterization, the culture-based method covered only 1.3-1.8% of the bacterial diversity determined by HTS. Moreover, neither Phreatobacter, nor Hyphomicrobium could be identified in the colonies, indicating that they are most likely not cultivable in the conditions stipulated by European standards.

Conclusions

  • Spatial distribution showed a clear homogeneity of communities between and within DWDSs.
  • Significant, but moderate, shifts in bacterial community composition were observed according to temporality.
  • Variation in relative abundance of opportunistic pathogen and faecal indicators followed climatic event.
  • Microbial monitoring using HTS appeared as a pertinent and useful tool, detecting fluctuations of bacterial populations and specific taxa with high sensitivity.

Contributor

Diana López-Farfán