Bradford-reactive Soil Protein Research Articles

COMPARISON OF GLOMALIN AND HUMIC ACID IN EIGHT NATIVE U.S. SOILS

Two important extractable fractions of soil organic matter (SOM) arehumic acid (HA) and glomalin-related soil protein (glomalin). Optimizing the purity of each fraction is necessary to correlate fraction quantity and molecular characteristics with soil quality. Manipulation of extraction sequence and controlled precipitation of HA were used to evaluate co-extraction of HA and glomalin. Eight bulk soil samples (0 to 10 cm depth) were collected from four U.S. states (Colorado, Nebraska, Maryland, and Georgia). In Experiment 1, glomalin extraction (50 mM citrate, pH 8.0, at 121 °C) was followed by HA extraction (0.1 N NaOH at room temperature), and Experiment 2 used the reciprocal sequence. Experiment 2 HA was precipitated stepwise at pH levels 2.5, 2.0, and 1.0. Gravimetric weight, Bradford-reactive soil protein (BRSP), and immunoreactive soil protein (IRSP), along with percentages of C, N, H, and Fe, were used to compare glomalin and HA. The HA fraction from Experiment 2 contained 2-fold greater amounts of BRSP than HA from Experiment 1 and showed that pre-extraction of glomalin improved the purity of HA. The glomalin fraction from Experiment 1 contained 1.5 times the BRSP of glomalin from Experiment 2 and was twice the gravimetric weight. BRSP and gravimetric weight were concentrated in HA that precipitated at pH 2.5 or 2.0 and percentage IRSP was significantly higher in the pH 2.5 precipitate. The results indicate that glomalin should be extracted first and examined as a biomolecule separate from the humic acid mixture. Percentages C, H, N, and Fe in glomalin varied across soils and experiments. In seven soils, the changes inFe percentage in glomalin from Experiment 1 to 2 were significantly correlated with the changes in glomalin weight and %C. Iron in glomalin from Experiment 1 was related to soil pH and clay content, whereas soil organic C was positively and significantly correlated with Experiment 1 glomalin BRSP and IRSP. In Experiment 1, a recalcitrant pool of glomalin was released by treating soil with NaOH, suggesting that a fraction of glomalin is difficult to remove from soil and glomalin extraction efficiency could be improved. Refinements to extraction and purification protocols such as pretreatment of soils with HCl and sequential extraction can facilitate studies on organic matter structure and function.

Plant invasion of native grassland on serpentine soils has no major effects upon selected physical and biological properties

Plant invasions alter soil microbial community composition; this study examined whether invasion-induced changes in the soil microbial community were reflected in soil aggregation, an ecosystem property strongly influenced by microorganisms. Soil aggregation is regulated by many biological factors including roots, arbuscular mycorrhizal fungal hyphae, and microbially-derived carbon compounds. We measured root biomass, fungal-derived glomalin-related soil protein (GRSP), and aggregate mean weight diameter in serpentine soils dominated by an invasive plant ( Aegilops triuncialis (goatgrass) or Centaurea solstitialis (yellow starthistle)), or by native plants ( Lasthenia californica and Plantago erecta, or Hemizonia congesta). Root biomass tended to increase in invaded soils. GRSP concentrations were lower in goatgrass-dominated soils than native soils. In contrast, starthistle dominated soil contained a higher amount of one fraction of GRSP, easily extractable immunoreactive soil protein (EE-IRSP) and a lower amount of another GRSP fraction, easily extractible Bradford reactive soil protein (EE-BRSP). Soil aggregation increased with goatgrass invasion, but did not increase with starthistle invasion. In highly aggregated serpentine soils, small increases in soil aggregation accompanying plant invasion were not related to changes in GRSP and likely have limited ecological significance.

Protein accumulation and distribution in floodplain soils and river foam

AbstractMany processes contribute to nutrient transfer from terrestrial to aquatic systems, but in most cases the contribution of particular organisms is unknown. In this study, we explore how a Bradford‐reactive soil protein (BRSP) produced by arbuscular mycorrhizal fungi may provide nutrients to river ecosystems. Along a floodplain in Montana, we extracted BRSP from soils and related the protein concentrations to the age of soil surfaces. We identified BRSP in surface soils, as well as to a depth of 1.4 m, and found that the protein accumulates through time. We also detected BRSP in foam from five rivers in the western United States. Experiments were conducted that demonstrate that the protein may be leached or washed from soils and become a constituent of foam when mixed into turbulent water. We propose that terrestrially derived soil protein may enter rivers via erosion and leaching and serve as a nutrient source for aquatic organisms.

The role of glomalin in soil erosion

Glomalin is a glycoprotein, a sugar protein compound that might trigger the formation of soil. In this study we analyze the different organic matters which inhance mycorrhizal fungi and produce glomalin which is dependent upon the types of organic matter. The more glomalin in a particular soil, the soil probably is better. The amount of glomalin in the soil increased as a degree of interdependence increased between plants and arbuscular mycorrhizal fungi. These fungi produce glomalin and live inside plant roots and in the surrounding soil. Growth of Arbuscular mycorrhizal fungi under field conditions was estimated within growth mesh bags which contain different organic matter. After six months these mesh bags were harvested. These soil were analysed in Montana University, USA by two detection methods utilized to quantify Glomalin related soil protein (GRSP): Bradford protein assay, yielding Bradford reactive soil protein (BRSP), and an enzyme-linked immunosorbent assay (ELISA: using the monoclonal antibody Mab32B11 developed against crushed spores of Glomus intraradices,yielding the immunoreactive soil protein. The amount of GRSP in the mesh bags was positively related to organic matter addition. Furthermore, GRSP content was positively correlated to NLFA 16:1ù5 as well as to PLFA 16:1ù5 and bacterial PLFAs .In contrast no correlation was found between spore number and neither fatty acids nor GRSP. Key words : Organic matters; Arbuscular mycorrhizal fungi; Glomalin; Climate change; Green house gas. DOI: http://dx.doi.org/10.3126/sw.v9i9.5524 SW 2011; 9(9): 82-85