Microbial diversity and biosignatures of amorphous silica deposits in orthoquartzite caves

Abstract

Chemical mobility of crystalline and amorphous SiO2 plays a fundamental role in several geochemical and biological processes, with silicate minerals being the most abundant components of the Earth’s crust. Although the oldest evidences of life on Earth are fossilized in microcrystalline silica deposits, little is known about the functional role that bacteria can exert on silica mobility at non-thermal and neutral pH conditions. Here, a microbial influence on silica mobilization event occurring in the Earth’s largest orthoquartzite cave is described. Transition from the pristine orthoquartzite to amorphous silica opaline precipitates in the form of stromatolite-like structures is documented through mineralogical, microscopic and geochemical analyses showing an increase of metals and other bioessential elements accompanied by permineralized bacterial cells and ultrastructures. Illumina sequencing of the 16S rRNA gene describes the bacterial diversity characterizing the consecutive amorphization steps to provide clues on the biogeochemical factors playing a role in the silica solubilization and precipitation processes. These results show that both quartz weathering and silica mobility are affected by chemotrophic bacterial communities, providing insights for the understanding of the silica cycle in the subsurface.

Microbe‐Mediated Extracellular and Intracellular Mineralization: Environmental, Industrial, and Biotechnological Applications

“…The silica amorphization process in the Imawarì Yeuta cave is the first reported to be connected with microbes. [ 31 ] Silica precipitation and speleothem formation are induced by the activity of heterotrophic or autotrophic filamentous bacteria such as cyanobacteria. The presence of tubular casts and filamentous structures is attributed to the silicification of microbe cells and metabolic products.…”

Physicochemical Parameters Affecting the Distribution and Diversity of the Water Column Microbial Community in the High-Altitude Andean Lake System of La Brava and La Punta

“…The influence of silica on the genera Marinobacter, Marinicella, Methylophafa, Marinimonas, and Haliea ( Figure 5) can be associated with the metabolic processes that allow hard silica to precipitate in lake sediments, as suggested by Sauro et al [69]. In their work, water bodies containing silica were analyzed, showing a predominance of chemotrophic microbial communities of the phylum Proteobacteria and different classes, among which the class Gamma-proteobacteria was predominant.…”

“…These communities were associated with the biomineralization processes of silica, which causes its precipitation from an aqueous amorphous state to a hard-solid state. This process occurs through an increase in pH mediated by microbial metabolism, e.g., nitrogen fixation, decomposition of proteins or amino acids, degradation of urea, and consumption of CO 2 [69]. Silica can also be solubilized by different species of the genus Pseudomona [70], which happens to be more abundant in the main body of La Punta (P01-P04) and in the isolated bodies of La Brava (B08-B10).…”

Diversity and structure of soil microbiota of the Jinsha earthen relic

“…Currently, only 1% of all microorganisms can be cultured under laboratory conditions, thus molecular methods for genome characterization are important tools for defining the diversity and composition of microbial communities [24]. Pyrosequencing of 16S rRNA genes is a well-validated high throughout sequencing technique that affords a powerful approach for investigating the microbial communities in the environment [25][26][27], and has been used successfully to define the composition and diversity of microbial communities from various environments, such as samples from seawater, caves and soil [28][29][30][31][32].…”