Ubiquitous genome streamlined Acidobacteriota in freshwater environments

Area of Science:

• Microbiology
• Genomics
• Environmental Science

Background:

• Acidobacteriota are common in soil but understudied in freshwater.
• UBA12189 is an uncultivated, genome-streamlined Acidobacteriota lineage in aquatic environments.
• Detailed genomic analysis of this lineage was lacking.

Purpose of the Study:

• To analyze the genomes of the UBA12189 lineage from diverse freshwater environments.
• To understand the metabolic capabilities and adaptations of genome-streamlined bacteria in freshwater.
• To propose a new genus and species for this lineage.

Main Methods:

• Analysis of 66 UBA12189 MAGs (Metagenome-Assembled Genomes), including one complete genome.
• CARD-FISH (Catalyzed Reporter Deposition Fluorescence In Situ Hybridization) for ecological role determination.
• Comparative genomic analysis with other streamlined bacteria.

Main Results:

• UBA12189 possesses small genomes (<1.4 Mbp), low GC content, and a diverse pangenome.
• This lineage is abundant in freshwater lakes from surface to deep waters and appears free-living.
• Genome reduction resulted in limited metabolic pathways but retained key genes like proteorhodopsin and heme biosynthesis.

Conclusions:

• The new genus Acidiparvus (with species A. lacustris and A. fluvialis) is proposed.
• Acidiparvus represents the first described genome-streamlined lineage within Acidobacteriota.
• This lineage is a slow-growing, free-living scavenger in freshwater ecosystems.