Mineral Weathering By Silicate Bacteria And Its Preliminary Application

This paper focuses on minerals and soil weathering by silicate bacteria in culture experiments and preliminary studies the soil physical characteristic affected by silicate bacteria.A strain of silicate-dissolving bacteria HTK01, screened out of the Gansu loess, was identified by general methods and molecule biology technique . the potassium-dissoiving ability and phosphorus-dissoiving ability of the strain was each measured by ICP and colorimetry. three kinds of minerals and loess weathering by the silicate bacteria in culture experiments was studied by TEM and SEM to analyze the interfacial characteristic between bacteria and minerals and to examine chemical ingredients of minerals. Further, the mechanism of mineral weathering by the bacteria was discussed. Soil aggregates and soil water was measured by incubating the bacteria solution into the soil to study the bacteria effect on soil physical properties. At last, the strain was applied into plant growing.The experimental results indicated that this strain HTK01 is of bacilliform, measuring 0.9-1.3μm×3.0-7.5μm in size, with thick capsule in the cell surroundings. The capsule is generally several times large the bacterial bodies in size. The spores are rounded or elliptic in shape, and Gram-staining negative. The bacterial colony appears as shining glasslike structures and is hard to draw. Its optimal pH value is 7.0-8.0, its can endure 0.1%NaCl to 0.5%NaCl, as well as its optimal temperature is 30℃around. Based on biochemical and physiological identification, and 16SrDNA sequence analysis, the strain HTK01 was identified as Bacillus, mucilaginosus. because of silicate bacteria characterized by its abundant capsule and most of the useful performances of bacteria related to its capsule, several staining methods used for the capsule of silicate bacteria are be compared and improved.The strain's potassium-releasing capability was tested. It was found that silicate bacteria has different k-releasing ability for different kinds of minerals. The results indicated that the potassium content of inoculating silicate bacteria is higher than inoculating inactivated bacteria, k-feldspar increasing by 30.94%, biotite increasing by 39.49%,and phosphorite increasing by 15.72%. Contemporary, silicon and aluminum of the minerals were released by the strain HTK01. The measure of potassium-releasing in culture experiment has been improved. The capacity of silicate bacteria in dissolving P compounds was studied. In the case of Ca₃(PO₄)₂ as P source, the content of dissoluble phosphorous in the cultural solution increased 3.835μg/mL than the CK. When was Ca₃(PO₄)₂ replaced by leithin, dissoluble phosphorous was measured, which increased 0. 628μg/mL than the CK. The silicate bacteria was static cultured for 5 days, 10 days,20 days,40 days and 80days to study three kinds of minerals and loess weathering, by means of electron microscopes observation, the results showed that the bacteria indeed eroded the surface of the testing minerals, which were characteristic of round shapes and uneven surface. The mineral particles were covered with numerous bacteria. The content of dissoluble potassium, silicon and phosphorous have increased with the cultural time's postponement. It was showed that silicate bacteria has different solution ability for different kinds of minerals and with different cultural times, the results also showed that there is a correlation between the capability ofthe bacterium of minerals weathering and its capsular polysaccharides. The mechanisms of mineral weathering by silicate bacteria were also discussed.Studying on soil physical characteristic, the results showed that silicate bacteria had the abilities helpful to form soil aggregates, which could increase the quantity of soil large waterstable aggregates,that is to make them with particle sizes over 5mm and 2-5mm increase greatly. The soil water evaporation which is inoculated silicate bacteria solution can be inhibited better than inoculated inactivated bacteria solution and used germ-free water. When the bacteria was to inoculated soil, the soil saturated hydraulic conductivity decreased. However, the soil water evaporation and soil saturated hydraulic conductivity have no obvious difference among inoculated silicate bacteria solution, inactivated bacteria solution and germ-free water following increased cultural time.Pot and field experiments with silicate bacteria fertilizer added to soil showed that there were obvious increases in the fresh and dry weight of the clover stem highness, root length and root nodule quantity were better than the CK, and the clover growth was improved.