Environmental factors shaping cultured free-living amoebae and their associated bacterial community within drinking water network
Résumé
Free-living amoebae (FLA) constitute an important part of eukaryotic populations colonising drinking
water networks. However, little is known about the factors influencing their ecology in such environments.
Because of their status as reservoir of potentially pathogenic bacteria, understanding environmental
factors impacting FLA populations and their associated bacterial community is crucial. Through
sampling of a large drinking water network, the diversity of cultivable FLA and their bacterial community
were investigated by an amplicon sequencing approach, and their correlation with physicochemical
parameters was studied. While FLA ubiquitously colonised the water network all year long, significant
changes in population composition were observed. These changes were partially explained by several
environmental parameters, namely water origin, temperature, pH and chlorine concentration. The
characterisation of FLA associated bacterial community reflected a diverse but rather stable consortium
composed of nearly 1400 OTUs. The definition of a core community highlighted the predominance of
only few genera, majorly dominated by Pseudomonas and Stenotrophomonas. Co-occurrence analysis also
showed significant patterns of FLA-bacteria association, and allowed uncovering potentially new FLA -
bacteria interactions. From our knowledge, this study is the first that combines a large sampling scheme
with high-throughput identification of FLA together with associated bacteria, along with their influencing
environmental parameters. Our results demonstrate the importance of physicochemical parameters
in the ecology of FLA and their bacterial community in water networks.