Mapping total microbial communities and waterborne pathogens in household drinking water in China by citizen science and metabarcoding

Xinyi Wen^1,2,3Chutong Fang^1,4Lihan Huang^1,5Jiazheng Miao^1,6Yajuan Lin^1,7*

• ¹Duke Kunshan University, Kunshan, Jiangsu, China
• ²Nicholas School of the Environment, Duke University, Durham, North Carolina, United States
• ³Pratt School of Engineering, Duke University, Durham, North Carolina, United States
• ⁴Blum Center for Developing Economies, University of California, Berkeley, Berkeley, California, United States
• ⁵Department of Civil and Environmental Engineering, School of Engineering, Stanford University, Stanford, California, United States
• ⁶Department of Biomedical Informatics, Harvard Medical School, Boston, Massachusetts, United States
• ⁷Texas A&M University Corpus Christi, Corpus Christi, United States

Ensuring access to safe drinking water is one of the top priorities in public health, as waterborne diseases remain a significant global challenge. In China, microbial contamination in drinking water is of particular concern, and comprehensive surveys and monitoring of the drinking water microbiome are necessary. However, traditional culture-based microbial monitoring methods have significant limitations, and nationwide tap water survey/monitoring in China would require significant resources.Here, a cost-effective and culture-independent citizen science approach was developed to sample the microbiome in household drinking water (n = 50) from 19 provinces in China from December 2020 to August 2021, including a few opportunistic samples collected immediately after extreme weather events, such as the 2021 Henan Floods and Typhoon In-Fa's Landfall. Using a protocol optimized for low-biomass samples, 22 out of 50 tap water samples were successfully amplified, yielding DNA with a significant number of sequencing reads. Using 16S rRNA gene metabarcoding on pooled samples, we identified 7,635 Amplicon Sequence Variants (ASVs), revealing a diverse microbiome in household tap water. Alarmingly, pathogenic bacteria including Mycobacterium spp., Acinetobacter spp., and Legionella spp. were detected in all PCR-positive samples. Despite the limited number of samples, an increase in potential pathogenic ASVs, such as Salmonella enterica, was observed in local tap water samples from Changzhou following the landfall of Typhoon In-Fa. Overall, this study highlights the scalability and cost-effectiveness of citizen science as a tool for enhancing microbial monitoring and informs future public health strategies for water safety.