Purple sulfur bacteria fix N<sub>2</sub> via molybdenum-nitrogenase in a low molybdenum Proterozoic ocean analogue.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34362886.
- Also identified by DOI 10.1038/s41467-021-25000-z and PMC identifier 8346585.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Biological N<sub>2</sub> fixation was key to the expansion of life on early Earth. The N<sub>2</sub>-fixing microorganisms and the nitrogenase type used in the Proterozoic are unknown, although it has been proposed that the canonical molybdenum-nitrogenase was not used due to low molybdenum availability. We investigate N<sub>2</sub> fixation in Lake Cadagno, an analogue system to the sulfidic Proterozoic continental margins, using a combination of biogeochemical, molecular and single cell techniques. In Lake Cadagno, purple sulfur bacteria (PSB) are responsible for high N<sub>2</sub> fixation rates, to our knowledge providing the first direct evidence for PSB in situ N<sub>2</sub> fixation. Surprisingly, no alternative nitrogenases are detectable, and N<sub>2</sub> fixation is exclusively catalyzed by molybdenum-nitrogenase. Our results show that molybdenum-nitrogenase is functional at low molybdenum conditions in situ and that in contrast to previous beliefs, PSB may have driven N<sub>2</sub> fixation in the Proterozoic ocean.
Medical subject headings
- Chromatiaceae
- Molybdenum
- Nitrogen
- Nitrogen Fixation