Characterization of elemental release during microbe–basalt interactions at T=28°C

Abstract

This study used batch reactors to characterize the rates and mechanisms of elemental release during the interaction of a single bacterial species (Burkholderia fungorum) with Columbia River Flood Basalt at T = 28°C for 36 days. We primarily examined the release of Ca, Mg, P, Si, and Sr under a variety of biotic and abiotic conditions with the aim of evaluating how actively metabolizing bacteria might influence basalt weathering on the continents. Four days after inoculating P-limited reactors (those lacking P in the growth medium), the concentration of viable planktonic cells increased from $10 4 to 10 8 CFU (Colony Forming Units)/mL, pH decreased from $7 to 4, and glucose decreased from $1200 to 0 lmol/L. Mass-balance and acid-base equilibria calculations suggest that the lowered pH resulted from either respired CO 2 , organic acids released during biomass synthesis, or H + extrusion during NH 4 þ uptake. Between days 4 and 36, cell numbers remained constant at $10 8 CFU/mL and pH increased to $5. Purely abiotic control reactors as well as control reactors containing inert cells ($10 8 CFU/mL) showed constant glucose concentrations, thus confirming the absence of biological activity in these experiments. The pH of all control reactors remained near-neutral, except for one experiment where the pH was initially adjusted to 4 but rapidly rose to 7 within 2 days. Over the entire 36 day period, P-limited reactors containing viable bacteria yielded the highest Ca, Mg, Si, and Sr release rates. Release rates inversely correlate with pH, indicating that proton-promoted dissolution was the dominant reaction mechanism. Both biotic and abiotic P-limited reactors displayed low P concentrations. Chemical analyses of bacteria collected at the end of the experiments, combined with mass-balances between the biological and fluid phases, demonstrate that the absence of dissolved P in the biotic reactors resulted from microbial P uptake. The only P source in the basalt is a small amount of apatite ($1.2%), which occurs as needles within feldspar grains and glass. We therefore conclude that B. fungorum utilized apatite as a P source for biomass synthesis, which stimulated elemental release from coexisting mineral phases via pH lowering. The results of this study suggest that actively metabolizing bacteria have the potential to influence elemental release from basalt in continental settings.

Influence of Forest Trees on the Distribution of Mineral Weathering-Associated Bacterial Communities of the Scleroderma citrinum Mycorrhizosphere

“…4) to weather biotite. The mineral weathering efficacy of strains of the Burkholderiales was previously reported for other minerals, such as apatite, basalt, and granite (33,(52)(53). We also revealed that the weathering potential varies greatly depending on the isolates: about 40% of the isolates belonging to the Burkholderia genus did not weather biotite under our experimental conditions (Fig.…”

Microbial colonization in diverse surface soil types in Surtsey and diversity analysis of its subsurface microbiota

“…monoxide as a C and energy source (Dunfield and King, 2004;King and Weber, 2008) or by growing heterotrophically using trace amounts of organic carbon (Cockell et al, 2009;Wu et al, 2007). Studies on the microbiota of volcanic terrains have only emerged within the past few years, revealing that such habitats are capable of harbouring significant microbial diversity, despite their extreme nature (GomezAlvarez et al, 2007;Kelly et al, 2010).…”

Microbial Mineral Weathering for Nutrient Acquisition Releases Arsenic

“…It is well known that bacteria can obtain nutrients from solid-phase minerals (1,4,5,36,47). Subsurface environments are oligotrophic, and bacteria have been shown to preferentially weather minerals that contain phosphate and ammonia, both required for growth (36,37).…”

“…Specifically, experiments with basalt and granite have shown that it can weather these rocks and release phosphate into the environment (47,48). Members of the Burkholderia genus have been isolated from granitic soils (48) and have been shown to be efficient at mineral weathering (40).…”