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Acidobacteriota

life science Maturity 11-13 Next article →

Acidobacteriota is a large phylum of Gram-negative bacteria. These microbes are found in many different environments across the Earth. They live in soil, oceans, and even dark caves. Some can survive in hot springs or decomposing wood. You can even find them in soil that contains metal. They are especially common in soil habitats. In some places, they make up 52% of the total bacterial community.

Many members of this phylum are acidophilic, meaning they thrive in acidic conditions. For example, Acidobacterium capsulatum was the first member described. Some bacteria from acid mine drainage are highly adapted to low pH levels. These specific strains live in environments with a pH between 2 and 3. This adaptation may come from cell specialization or enzyme stability. Other members thrive in different settings depending on nutrients and pH levels.

Scientists classify these bacteria into 26 accepted subdivisions. They use the sequencing of 16S rRNA gene regions to do this. Subdivision 1 is the largest and contains the most known species. It includes 11 known genera and 40 conclusive species. Other subdivisions include 3, 4, 8, 10, and 23. Much of this variety was discovered in soils contaminated with uranium. Subdivision 2 contains unclassified members that can contaminate DNA extraction kits.

Most Acidobacteriota are aerobes, which means they use oxygen to live. However, some members in subdivisions 8 and 23 are anaerobes. These do not require oxygen to function. Some soil strains have the genomic potential to breathe oxygen even at very low concentrations. Many are also considered oligotrophic bacteria. This means they are successful in environments with very little organic carbon. This ability allows them to dominate in nutrient-poor habitats.

The history of studying this phylum is relatively recent. The first species, Acidobacterium capsulatum, was discovered in 1991. In 1997, researchers recognized them as a distinct clade. They were not officially recognized as a full phylum until 2012. The first genome was sequenced in 2006. Today, this is a growing field of microbiology. Much of what we know is still changing as new data emerges.

Metabolism in this phylum is quite complex and diverse. Many members are heterotrophic, meaning they get energy from organic compounds. Some in subdivision 1 use D-glucose, D-xylose, or lactose for carbon. Subdivision 4 members have been found to use chitin as a carbon source. Interestingly, only one species, Telmactobacter bradus, can process cellulose. Scientists believe xylan degradation is the most universal carbon breakdown ability.

Researching these bacteria is difficult because they are hard to grow in labs. Most species have not been cultured in a controlled environment. Scientists have tried using high amounts of CO2 and low nutrients to help. Even so, only about 30% of subdivisions have documented species. This makes it hard to match DNA sequences with actual behavior. We are still learning how they process nitrogen and carbon.

Acidobacteriota also play a role in the nitrogen cycle. While there is no clear evidence of nitrogen fixation, some members show specific traits. Geothrix fermentans can reduce nitrate and contains the norB gene. This gene was also found in Koribacter verstailis and Solibacter usitatus. Members of subdivision 1 contain the nirA gene. Most genomes show they can take up ammonium through special transporter genes. This helps connect these microbes to the wider ecosystem.

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