# Effect of rainfall on metagenomics in a sewage environment in Hongta District, Yuxi city, Yunnan Province

## TL;DR

This study analyzed sewage microbiomes in Hongta District, finding that rainfall and location significantly affect microbial diversity and antibiotic resistance.

## Contribution

The study provides the first systematic analysis of sewage microbiomes in Hongta District, revealing the impact of rainfall and site on microbial composition and antibiotic resistance.

## Key findings

- Bacteria dominated the microbiome (98.31%), with Proteobacteria as the most abundant phylum.
- Rainfall significantly influenced the composition of microbial taxa at family, genus, and species levels.
- Urban sites showed higher abundance of virulence and multidrug resistance genes compared to rural sites.

## Abstract

Hongta District of Yuxi city is located in the central region of Yunnan Province, Southwest China. Previous studies have shown a high prevalence of enteric infectious diseases in the area, which may be related to sewage discharge. However, there has been no systematic analysis of the microbiome in sewage in this area. In this study, we investigated environmental sewage in Hongta District, Yuxi city, Yunnan Province.

Surveillance was conducted in Hongta District, Yuxi city, for a period of one year. At both its urban and rural sites, sewage samples were collected for metagenomic sequencing.

The results revealed that in the sewage samples, bacteria accounted for 98.31% of the total microbiome, followed by Archaea (1.05%), Viruses (0.30%) and Eukaryota (0.34%). At the phylum level, Proteobacteria was the taxon with the highest relative abundance, accounting for 57.57% of all samples, followed by Firmicutes (17.17%), Bacteroidetes (12.23%), Actinobacteria (7.10%), and Synergistetes (1.45%). At the genus level, the taxa with the highest relative abundances of all the microbiomes were Acidovorax (6.63%), Pseudomonas (4.98%), Acinetobacter (4.23%), Comamonas (3.85%), and Aliarcobacter (2.78%). The diversity of the samples grouped by site and rainfall formed their own clusters, but only the compositions of different taxa grouped by rainfall significantly differed (P = 0.038 at the family, P = 0.019 at the genus and P = 0.005 at the species level). In general, the abundance of several taxa at the family, genus and species levels in the dry season group was higher (P < 0.05) than that in the rainy season group according to the Kruskal–Wallis test. The relative abundance s of most virulence genes were higher at urban sites than at rural sites, while those in the rainy season was higher than those in the dry season. The distribution of antibiotic resistance genes (ARGs) in urban and rural sewage was significantly different (P = 0.018). The relative abundance of multidrug resistance genes in urban sewage was higher than that in rural sewage, and the relative abundance of most resistance genes in the dry season group was higher than that in the rainy season group.

In general, the abundance and distribution features of the sewage microbial communities in the Hongta District of Yuxi city were affected by site and rainfall factors, with significant regional and temporal specificity. Strengthening the surveillance of environmental sewage and improving discharge methods are highly important for ensuring public health security.