Abstract
Candidate Phyla Radiation (CPR) bacteria and DPANN archaea are uncultivated, small-celled symbionts often detected in groundwater. However, variations in CPR/DPANN organism abundance, distribution, taxonomic diversity, and degree/nature of host association with groundwater chemistry remain understudied. Here, we performed genome-resolved metagenomic characterization of one agriculturally-impacted and seven pristine groundwater microbial communities in California, recovering 746 dereplicated CPR and DPANN genomes. Our finding of up to 31% CPR bacteria and 4% DPANN archaea in the pristine sites, which serve as local sources of drinking water, may hold health relevance, given growing awareness of the presence of CPR/DPANN organisms in human microbiomes and their association with disease. There is little species-level genome overlap across groundwater sites, indicating that CPR and DPANN communities are highly differentiated according to host populations and physicochemical conditions. Cryo-TEM imaging and genomic analyses indicate that CPR growth may be stimulated by attachment to the surface of host cells, and identified CPR and DPANN lineages with particularly prevalent and/or resilient host cell attachment. These results establish the huge but site-specific diversity of CPR bacteria and DPANN archaea coexisting with diverse hosts in groundwater aquifers, and raise important questions about potential impacts on human health.
Competing Interest Statement
The authors have declared no competing interest.