Release of phosphorus and silicon from minerals by soil microorganisms depends on the availability of organic carbon

Goethite-Bound Phosphorus in an Acidic Subsoil Is Not Available to Beech (Fagus sylvatica L.)

“…Results of our mesocosm experiment fit to those of Pastore et al (2020), who showed that goethite-associated phosphate is hardly available to microorganisms especially at low concentrations of easily degradable organic C, which is an important driver for P release by microorganisms (Brucker et al, 2020). In our mesocosm experiment, C-limitation by microbes might, thus, be a further reason why microbes did not release sufficient P from goethite in our C-poor subsoil.…”

Contribution of Arbuscular Mycorrhizal Fungi, Phosphate–Solubilizing Bacteria, and Silicon to P Uptake by Plant

“…These bacteria have been isolated from different habitats, such as rice plant rhizospheres (Kang et al, 2017;Chandrakala et al, 2019), from rice field soil samples (Vasanthi et al, 2013), weathered feldspar surfaces (Sheng and He, 2006), weathered rock surfaces (Gu et al, 2015), weathered rock (purple siltstone) surfaces (Chen et al, 2015), pond sediments, river water, soils, and talc minerals (Umamaheswari et al, 2016), potassium mine tailings (Huang et al, 2013), quercus petreae oak mycorrhizal roots surroundings (Calvaruso et al, 2010), and weathered rocks (Wang et al, 2015). Some mechanisms which SSB could utilize to release soluble silica from insoluble silicates include: (i) production of organic acids including citric, tartaric, acetic, gluconic, hexadecanoic, malic, oxalic, phthalic, oleic, heptadecanoic, and hydroxypropionic acids (Vassilev et al, 2006;Vasanthi et al, 2018), which have metal complexing properties that may bind with aluminum and iron silicates and render silicates soluble, also provide protons (H + ) for protonation for silicate hydrolysis (Duff and Webley, 1959;Avakyan et al, 1986;Drever and Stillings, 1997); (ii) inorganic acid production (i.e., oxidation of sulfur, reduction of sulfides to sulfuric acid, oxidation of ammonia to nitrates, and conversion of nitrates to nitric acid, which can act on silicates); (iii) synthesis and discharge of carbonic anhydrase that catalyzes the interconversion between carbon dioxide produced by soil microbes and water, and the dissociated ions of carbonic acid (Brucker et al, 2020), which promotes the microbial conversion of silicate minerals as observed in orthoclase degradation to kaolinite (Waksman and Starkey, 1924). In addition, CO 2 sequestration in basaltic acquifers and the associated carbonate mineralization might maintain an environment suitable for silicate mineral dissolution (Pokrovsky et al, 2011); (iv) production of siderophores, which bind and transport iron(III) which can play a part in silicate solubilization by scavenging iron from silicate minerals as observed in hornblende degradation (Kalinowski et al, 2000); (v) the reduction of sulfates and production of H 2 S, which reacts with cations like Ca and Fe of silicate minerals forming sulfides and thus rendering silicate solubilization (Ehrlich et al, 2015); (vi) absorption and binding of the inorganic silicate ions on bacterial surfaces, due to having ionizable carboxylates and phosph...…”

“…AMF hyphae are also rapid channels for the recently produced photosynthates, which can attract PSB and promote their growth ( Kaiser et al, 2015 ). In addition, it has been found that the availability of easily decomposable organic compounds limits microbial P solubilization in soil extracts from phosphate minerals ( Brucker and Spohn, 2019 ; Brucker et al, 2020 ). Saprotrophic phosphate solubilizing microorganisms in mineral soils generally lack sufficient carbon ( Demoling et al, 2007 ; Heuck et al, 2015 ) because most organic carbon in soils is protected from sorptive or recalcitrant microbial decomposition or is simply spatially inaccessible ( De Nobili et al, 2001 ; Dungait et al, 2012 ).…”

“…Phosphate–solubilizing bacteria generally have the ability to weather silicates, likely because basic metabolic activities like organic acid production and respiration can cause the weathering of minerals ( Brucker et al, 2020 ). PSB mainly solubilize insoluble Pi by acidifying the microenvironment ( Etesami, 2020 ).…”

“…It is noteworthy that microbial P solubilization is not influenced by the soil P availability. For example, in a study ( Brucker et al, 2020 ), adding P (100 mg of ground apatite) to soil extracts from soils with various P fractions (bioavailable P between 0.6 to 38 mg kg –1 and total P between 0.42 to 1.23 g kg –1 ) and degree of weathering, which had been incubated 28 days, did not substantially reduce P solubilization rates, which indicates that the P availability does not affect the microbial soil P solubilization. It is probable that microbial P solubilization is not driven by the microbial P demand but rather is a side effect of microbial metabolism.…”