Microbially mediated aluminosilicate formation in acidic anaerobic environments: A cell‐scale chemical perspective

Abstract

Through the use of scanning transmission electron microscopy (STEM) combined with other complementary techniques (SEM, cryo-TEM, HRTEM, and EELS), we have studied the interaction of microorganisms inhabiting deep anoxic waters of acidic pit lakes with dissolved aluminum, silica, sulfate, and ferrous iron. These elements were close to saturation (Al, SiO 2 ) or present at very high concentrations (0.12 m Fe(II), 0.12-0. However, these features could also denote biomineralization by active bacterial cells as a detoxification mechanism, a possibility which should be further explored. We discuss the significance of the observed Al/microbe and Si/microbe interactions and the implications for clay mineral formation at low pH. K E Y W O R D SAluminum, aluminosilicate, acidic pit lake, acidophilic bacteria, biomineralization, metal-microbe interaction minerals in Amazonian rivers. The formation of amorphous aluminosilicates around cells of Bacillus subtilis was also observed by Fein, Scott, andRivera (2002). It is now assumed that clay biomineralization is a complex process that involves different stages of metal-microbe interactions, metal substitution, and crystallization (e.g., Konhauser, 2007;Konhauser & Urrutia, 1999;Tazaki, 2006). | INTRODUCTION AND OBJECTIVESDepending on water chemistry and the bacterial species involved in the biomineralization process, clay minerals of bacterial origin can be submicron to nanometric in size, display varied morphology (e.g., formless, ball-like, and layered), and exhibit varied composition (e.g., kaolinite-like, halloysite-like, nontronitic, and chloritic). These so-called bio-clays may form under both experimental and natural conditions (Tazaki, 1997(Tazaki, , 2006. The association between bacterial surfaces and aluminosilicates is considered to be promoted by the adsorption of Si on Fe and Al oxides, which are electrostatically bound to the bacterial surface, rather than by direct interactions (Fein et al., 2002;Konhauser, 2007 At low pH, the solubility of Al is significantly increased and this metal is present at important concentrations, being among the most abundant metal cations in acid mine drainage, acidic soils pore waters, and geochemically similar environments (e.g., Lindsay & Walthall, 1996;Nordstrom, 1982). However, the interaction of aluminum with microorganisms in these acidic environments has been studied to a comparatively lesser extent. This metal is known to be highly toxic to most aquatic microorganisms (Garcidueñas & Cervantes, 1996;Yokel & Golub, 1997), but the strategies and detoxification mechanisms of aci- | GEOCHEMICAL AND MICROBIOLOGICAL FRAMEWORK | HydrogeochemistryWe focused on Herrerías-Guadiana (GUA) and Cueva de la Mora at extremely acidic conditions (e.g., Sánchez-España et al., 2013 (Table S1) and carbon dioxide (up to 5 g/L; Sánchez-España et al., 2014), and a pH slightly above 4.0, which is close to the typical pH for Al precipitation in these environments ( Figure S1). | MicrobiologyIdentities of bacterial isolates (based on 16S rRNA...

Microbial Communities of Polymetallic Deposits’ Acidic Ecosystems of Continental Climatic Zone With High Temperature Contrasts

“…There, the phosphate was found to be at higher concentrations in the anaerobic monimolimnion zone in comparison to the aerobic mixolimnion. One could also suggest that a part of microbial community might be associated with clay mineral formation, as Sánchez-España et al (2018) earlier showed in acidic pit lake ecosystem in the Iberyan Pyritic Belt. However, relatively high abundance of iron cycling organisms in Sherlovaya Gora pit lake indicates the possibility of active Fe(II) and Fe(III) compounds turnover in the system.…”

Metagenomic and Metatranscriptomic Study of Microbial Metal Resistance in an Acidic Pit Lake

“…Previous studies using high-resolution scanning/transmission electron microscopy of samples collected from various depths in CM showed cells encrusted with mineral precipitates [82,83]. Extracellular polymeric substances (EPS) containing polysaccharides can sorb metals, providing another mechanism for microbial metal resistance [82].…”

Glycerol amendment enhances biosulfidogenesis in acid mine drainage-affected areas: An incubation column experiment

“…Rod-shaped cells showed different degree of Fe coating ( Figure 8C ), whereas filamentous cells had very little and cocci had no mineral precipitates in direct contact with their membranes. Previous studies by Scanning Transmission Electron Microscopy (STEM) and Electron Energy Loss Spectroscopy (EELS) have demonstrated that these Fe-coatings in anaerobic bacterial cells inhabiting deep layers of acidic pit lakes consist in Fe(II)-SO 4 ionic complexes adsorbed on carboxylic groups of the cell membrane ( Sánchez-España et al, 2018 ). These coated bacteria were the only ones, that were preserved after the plasma cleaning procedure and under the vacuum conditions of SEM, showing up as external molds ( Figures 7A,B,E ).…”