# Unveiling Global Diversity of Patescibacteriota and Functional Interactions with Host Microbes

## TL;DR

This study explores the global diversity of Patescibacteriota bacteria and their interactions with host microbes across various ecosystems.

## Contribution

The study introduces rpS3 as a reliable marker for tracking Patescibacteriota diversity and reveals their functional interactions with host bacteria.

## Key findings

- Patescibacteriota shows extensive taxonomic diversity and community heterogeneity across eight ecosystems.
- Patescibacteriota interacts with host bacteria through metabolic pathway cascades, such as helping sulfate-reducing bacteria resist nitrite stress.
- The study identifies potential functional synergies between Patescibacteriota and ammonia-oxidizing bacteria via NorB.

## Abstract

Patescibacteriota, also known as Candidate Phyla Radiation (CPR), is a diverse clade of ultra‐small bacteria with an epibiotic lifestyle. Despite their ubiquity across diverse ecosystems and ecological importance in microbial networks, the global distribution of Patescibacteriota and functional interactions with their host organisms remain largely unknown. Here, by leveraging comprehensive Patescibacteriota genomic resources and global multi‐habitat metagenomic datasets, it is demonstrated that ribosomal protein S3 (rpS3) as a reliable phylogenetic marker, enabling accurate recovery of Patescibacteriota diversity from short‐read metagenomes. Using this framework, extensive taxonomic diversity and pronounced community heterogeneity are uncovered across eight ecosystems. Through network analysis and genome‐wide functional screening, habitat‐specific co‐occurrence patterns are also revealed between Patescibacteriota and host‐associated bacteria, especially potential functional synergies mediated by metabolic pathway cascades. Notably, Patescibacteriota‐encoded NirK may assist sulfate‐reducing bacteria in resisting nitrite stress, while NorB can mitigate nitric oxide toxicity for complete ammonia‐oxidizing bacteria. Taken together, this study highlights the underappreciated diversity of Patescibacteriota and elucidates its important role in supporting host metabolism through complementary biochemical functions, offering new insights into its ecological significance and evolutionary adaptations in the global ecosystem.

Patescibacteriota represents a diverse group of ultra‐small epibiotic bacteria, which is largely overlooked. By integrating ribosomal protein S3‐based community profiling with MAG‐based metabolic potential analyses, this study provides new insights into their distribution, diversity, and potential interactions with other bacteria across diverse metagenomes.