Laboratory Tools to Quantify Biogenic Dissolution of Rocks and Minerals: A Model Rock Biofilm Growing in Percolation Columns

Abstract

Sub-aerial biofilms (SAB) are ubiquitous, self-sufficient microbial ecosystems found on mineral surfaces at all altitudes and latitudes. SABs, which are the principal causes of weathering on exposed terrestrial surfaces, are characterized by patchy growth dominated by associations of algae, cyanobacteria, fungi and heterotrophic bacteria. A recently developed in vitro system to study colonization of rocks exposed to air included two key SAB participants -the rock-inhabiting ascomycete Knufia petricola (CBS 123872) and the phototrophic cyanobacterium Nostoc punctiforme ATCC29133. Both partners are genetically tractable and we used them here to study weathering of granite, K-feldspar and plagioclase. Small fragments of the various rocks or minerals (1-6 mm) were packed into flow-through columns and incubated with 0.1% glucose and 10 µM thiamine-hydrochloride (90 µL min −1 ) to compare weathering with and without biofilms. Dissolution of the minerals was followed by: (i) analysing the degradation products in the effluent from the columns via Inductively Coupled Plasma Spectroscopy and (ii) by studying polished sections of the incubated mineral fragments/grains using scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analyses. K. petricola/N. punctiforme stimulated release of Ca, Na, Mg and Mn. Analyses of the polished sections confirmed depletion of Ca, Na and K near the surface of the fragments. The abrupt decrease in Ca concentration observed in peripheral areas of plagioclase fragments favored a dissolution-reprecipitation mechanism. Percolation columns in combination with a model biofilm can thus be used to study weathering in closed systems. Columns can easily be filled with different minerals and biofilms, the effluent as well as grains can be collected after long-term exposure under axenic conditions and easily analyzed.

In Vivo Entombment of Bacteria and Fungi during Calcium Oxalate, Brushite, and Struvite Urolithiasis

“…Additionally, microbes also cause dissolution across a wide range of rock types, most commonly via secretion of metabolic byproducts such as organic acids and production of biofilms. These processes, which make significant contributions to biogeochemical cycles in everything from natural rock formation to building stone degradation, have previously been well documented in both field and controlled laboratory conditions (34). Overall, microbiallymediated mineral precipitation and dissolution is ubiquitous on Earth (6).…”

An advanced genetic toolkit for exploring the biology of the rock-inhabiting black fungus Knufia petricola

“…K. petricola strain A95 (CBS 123872) was isolated from marble of the Philopappos Monument in Athens (Greece) and possesses all the characteristics of microcolonial black fungi. It grows moderately well in culture and is already intensively used in studies of mineral weathering and symbiotic interactions with the cyanobacterium Nostoc punctiforme [24][25][26][27][28][29][30][31][32][33] . The annotated genome sequence of A95 (F. Heeger et al submission to NCBI in preparation) along with protocols for PEG/CaCl 2 -mediated transformation of protoplasts 34 provided a framework for the efficient genetic engineering of K. petricola.…”

The Ecology of Subaerial Biofilms in Dry and Inhospitable Terrestrial Environments

“…Sarcinomyces petricola ) [106] as a heterotrophic component [8]. Through this model, Seiffert and colleagues [107,108] successfully studied the biological impact of the consortium on weathering granite and related minerals in a new setting of a geomicrobiologically modified percolation column. Villa et al [74] proposed a laboratory model of SABs composed of the unicellular cyanobacterium Synechocystis sp.…”