# Microbial Biofilms Dynamics and Functionality in an Urban Mycobacterium-Dominated Drinking Water Distribution System

## TL;DR

This study explores how biofilms form in urban drinking water systems, focusing on Mycobacterium and their impact on water quality and safety.

## Contribution

The study identifies key microbial taxa and novel viral elements involved in biofilm dynamics and antibiotic resistance in a Mycobacterium-dominated system.

## Key findings

- Biofilm communities were more functionally diverse than water communities and correlated with Mycobacterium pathogens and antibiotic resistance genes.
- 22% of identified microbial taxa were strongly responsible for biofilm formation and matrix remodeling.
- New putative Mycobacterium phages were detected that may destabilize biofilms by targeting mycolic acids.

## Abstract

Microbial communities in drinking water distribution
systems (DWDS)
develop primarily as biofilms on pipe surfaces. Despite their impact
on water quality, infrastructure maintenance, and biosafety, biofilms
are not routinely controlled. In this study, we investigated the bacterial
community dynamics and functionality in an urban chlorinated DWDS,
dominated by Mycobacterium, through
a multiphasic approach which included 16S rRNA gene metabarcoding,
metagenomics and microscopy. Our results showed that biofilm communities
were more functionally diverse compared to those from water and that
the biofilm maturity was positively correlated with the prevalence
of potential Mycobacterium emerging
pathogens and a broader distribution of antibiotic resistance genes
(ARGs) within the microbial community. The reconstruction of metagenome-assembled
genomes (MAGs) and the corresponding genomospecies allowed the identification
of key microbial taxa involved in the biofilm matrix remodeling, with
22% of them strongly responsible for biofilm formation. A diverse
and novel viral community was detected across the system, including
new putative Mycobacterium phages that
might act against mycolic acids and thus contribute to biofilm destabilization.
Our findings enhance our understanding of DWDS microbial composition
and biofilm formation dynamics, focusing on “who does what”
and then providing a foundation for developing effective biofilm control
strategies in water distribution systems.