Microbiomes in drinking water treatment and distribution: a meta-analysis from source to tap

Abstract

A meta-analysis of existing available Illumina 16S rRNA datasets from drinking water source, treatment and DWDS were collated to compare changes in abundance and diversity throughout. Samples from bulk water and biofilm were used to assess principles governing microbial community assembly and the value of amplicon sequencing to water utilities. Individual phyla relationships were explored to identify competitive or synergistic factors governing DWDS microbiomes. The relative importance of stochasticity in the assembly of the DWDS microbiome was considered to identify the significance of source and treatment in determining communities in DWDS. Treatment of water significantly reduces overall species abundance and richness, with chlorination of water providing the most impact to individual taxa relationships. The assembly of microbial communities in the bulk water of the source, primary treatment process, and DWDS is governed by more stochastic processes, as is the DWDS biofilm. DWDS biofilm is significantly different to bulk water in terms of local contribution to beta diversity and in types of taxa present. Water immediately post chlorination has a more deterministic microbial assembly, highlighting the significance of this process in changing the microbiome although elevated levels of stochasticity in DWDS samples suggest that this may not be the case at customer taps. 16S rRNA sequencing is becoming more routine and may have several uses for water utilities including detection and risk assessment of emerging pathogens like Legionella, Bacteroides and Mycobacterium; assessing the risk of nitrification of DWDS; improved indicators of process performance and monitoring for significant changes in the microbial community to detect contamination. Combining this with other quantitative methods like flow cytometry will allow a greater depth of understanding of the DWDS microbiome.

Ecological Observations Based on Functional Gene Sequencing Are Sensitive to the Amplicon Processing Method

“…We conclude that, for AOB amoA , the BLCA method, despite resulting in a lower number of sequences identified to species level, resulted in a classification that made more sense from a phylogenetic point of view. This result is coherent with previous research showing the superiority of BLCA vs. NBC for the taxonomic assignment of 16S rRNA reads (36). However, the BLCA method performed much worse than NBC for the taxonomic assignation of nrfA sequences with the vast majority (98.8%) of unassigned sequences versus 18.8% for NBC.…”

“…NBC for the taxonomic assignment of 16S rRNA reads (36). However, the BLCA method performed much worse than NBC for the taxonomic assignation of nrfA sequences with the vast majority (98.8%) of unassigned sequences versus 18.8% for NBC.…”

“…By considering hit results from multiple databases, the BLCA approach is able to provide probabilistic-based confidence values at each taxonomic levels of this assignment. Previously, the BLCA method has been shown to provide better species-level resolution than the NBC for 16S rRNA sequences (35, 36). How they compare for functional genes has yet to be determined.…”

Bacterial populations in different parts of domestic drinking water systems are distinct and adapted to the given ambient temperatures

“…Drinking water from the distribution network enters buildings with a specific microbiome. The composition of the microbial community contained at the point of entry depends on local conditions and is influenced by the raw water source of the distributed drinking water (Thom et al, 2022), the underlying treatment process (Pinto et al, 2012;Bruno et al, 2018), seasonal variation, pipe materials, water age, and other parameters characteristic of the corresponding distribution network (Proctor and Hammes, 2015). The distributed drinking water quality is in most countries highly regulated and monitored for hygienic parameters.…”