Acidobacteriota

Acidobacteriota is a diverse lineage of Gram‑negative bacteria that was first discovered in acidic soils. It is placed within the domain Bacteria and comprises several phyla that are sometimes referred to as Acidobacteria. The group was formally recognized in the early 2000s when molecular phylogenetics revealed its distinctness from other bacterial lineages. Members are found globally, especially in terrestrial and aquatic habitats, and they constitute a significant fraction of microbial communities in environments ranging from forest soils to a variety of sediments.

Morphologically, Acidobacteriota cells are typically rod‑shaped, pleomorphic, or filamentous. They lack distinctive spores and generally exhibit low to moderate growth rates. Many species are acidophilic or acid-tolerant, with optimal growth pH values ranging from 4 to 7. They are chemoheterotrophic, using a variety of organic substrates, and some strains can oxidize polysaccharides, aromatic compounds, and even utilize hydrogen and formate as energy sources. Their cell envelopes contain complex lipids, and many possess type IV pili, which aid in motility and surface attachment.

Ecologically, Acidobacteriota play an essential role in carbon cycling. They contribute to the decomposition of plant material by breaking down complex polysaccharides such as cellulose, hemicellulose, and lignin derivatives. Additionally, they are involved in nitrogen turnover, participating in denitrification and nitrate reduction in some habitats. Their ability to persist in low‑nutrient, acidic conditions makes them important for ecosystem resilience, particularly in forested and peatland soils where they often dominate microbial communities.

Genomic analyses have revealed that Acidobacteriota genomes are highly variable in size, ranging from about 2.5 to 8 megabases, and they encode a wide array of carbohydrate-active enzymes. Many genes involved in stress response, metal transport, and secondary metabolite biosynthesis have been identified, suggesting adaptive strategies for diverse environments. Whole‑genome sequencing has also uncovered novel metabolic pathways and potential biotechnological applications, such as biofuel production and bioremediation of toxic compounds.

Acidobacteriota thus represent a taxonomically and ecologically significant bacterial group whose study enhances our understanding of microbial diversity, soil chemistry, and environmental adaptation.