Intracellular and extracellular mineralization of a microbial community in the Edmond deep-sea vent field environment

Microbial biomineralization in submarine hydrothermal environments provides an insight into the formation of vent microfossils and the interactions between microbes, elements and minerals throughout the geological record. Here, we investigate microbial biomineralization of a deep-sea vent community in the Edmond vent field and provide ultrastructural evidence for the formation of microfossils and biogenic iron-rich minerals related to Archaea and Bacteria. Environmental scanning electron microscopy (ESEM) analysis shows that filamentous and spiral microbes are encrusted by a non-crystalline silica matrix and minor amounts of iron oxides. Examination by transmission electron microscopy (TEM) reveals acicular iron-rich particles and aggregates that occur either intracellularly or extracellularly. A culture-independent molecular phylogenetic analysis demonstrates a diverse range of Bacteria and Archaea, the majority of which are related to sulfur metabolism in the microbial mats. Both Archaea and Bacteria have undergone silicification, in a similar manner to microorganisms in some terrestrial hot springs and indicating that silicification may be driven by silica supersaturation and polymerization. Formation mechanisms of intracellular and extracellular iron oxides associated with microbes are discussed. These results enhance our understanding of microbial mineralization in extreme environments, which may be widespread in the Earth's modern and ancient hydrothermal vent fields.