Intracellular silicification by early-branching magnetotactic bacteria

Area of Science:

• Biogeochemistry
• Microbiology
• Geochemistry

Background:

• Biosilicification, the biological formation of silica, is crucial to global biogeochemical cycles and has historically reduced oceanic dissolved silicon.
• Eukaryotes were long considered the primary drivers of silicon cycling; however, recent findings suggest prokaryotes may also significantly impact silicon dynamics.

Purpose of the Study:

• To investigate the potential underappreciated role of prokaryotes in the silicon (Si) cycle.
• To identify and characterize novel microorganisms involved in biosilicification.

Main Methods:

• Identification and phylogenetic analysis of a previously unknown magnetotactic bacterium.
• Characterization of intracellular amorphous silica globule formation within the bacterium.
• Analysis of the bacterium's affiliation with the phylum Nitrospirota and its deep-branching lineage.

Main Results:

• A novel magnetotactic bacterium capable of forming intracellular, amorphous silica globules was discovered.
• This bacterium belongs to a deep-branching group within the Nitrospirota phylum, known for forming magnetosomes and sulfur inclusions.
• The findings demonstrate intracellularly controlled silicification in prokaryotes.

Conclusions:

• Prokaryotes, specifically this newly identified bacterium, contribute to intracellular biosilicification.
• This discovery suggests a previously unrecognized prokaryotic influence on the biogeochemical silicon cycle during early Earth history.
• The findings necessitate a re-evaluation of the historical role of prokaryotes in global silicon cycling.