高效钾长石分解菌株的筛选、鉴定及解钾活性研究

目的 筛选高效的钾长石分解细菌,并进行初步鉴定和解钾活性测定.方法 采集湖南省桂东县钾长石开采区土壤,利用钾长石为唯一钾源的选择性培养基筛选分离解钾细菌,通过摇瓶释钾试验复筛高效解钾菌株;同时,利用ICP-OES测定解钾菌的释钾效率.采用形态特征观察、生理生化特性检测和基于16S rRNA基因序列的系统发育分析初步鉴定高效解钾菌株.结果 分离获得11株生长良好的钾长石分解细菌,其中菌株JKC1、JKC2、JKC5和JKC7的解钾能力较强,解钾率分别为11.00％、11.50％、12.70％和11.70％.经初步鉴定JKC1为Bacillus megaterium,JKC2为Bacillus aryabhattai,JKC5为Azotobacter chroococcum,JKC7为Microbacterium trichothecenolyticum.结论 菌株JKC1、JKC2、JKC5和JKC7是高效的钾长石分解菌,可作为微生物浸矿(钾长石)机制研究的候选菌株.     

Distinct Weathering Ability and Populations of Culturable Mineral-Weathering Bacteria in the Rhizosphere and Bulk Soils of Morus Alba

In this study, we isolated and compared the weathering effectiveness and population of mineral-weathering bacteria from the rhizosphere and bulk soils of Morus alba grown in a mineral-rich soil. Eighty-four isolates could release Si, Al, K, and Fe from potash feldspar. Weathering effectiveness and pattern of the isolates differed between the rhizosphere and bulk soils. The proportion of the highly effective Si, Al, K, and Fe solubilizers was significantly higher in the rhizosphere soils than in the bulk soils. Notably, the proportion of the highly effective acid-producing isolates was also significantly higher in the rhizosphere soils. The 84 mineral-weathering isolates were affiliated with 15 bacterial genera. Distinct mineral-weathering genera were observed between the rhizosphere and bulk soils. The results suggested that the highly effective mineral-weathering bacteria were selected in the rhizosphere soils and the mineral-weathering bacteria from the rhizosphere and bulk soils might weather potash feldspar through different mechanisms.     

Characterization of Rhizobium sp. Q32 Isolated from Weathered Rocks and its Role in Silicate Mineral Weathering

One mineral-solubilizing strain was isolated from weathered potassic trachyte surfaces and identified as Rhizobium sp. Q32 based on the 16S rRNA gene sequence analysis. The mineral (feldspar and biotite) dissolution potential and the physiological characteristics of the bacterium were investigated. Laboratory mineral dissolution experiments indicated that inoculation with the live bacterium significantly increased feldspar and biotite dissolution by a factor of 1.2–4.7 for Si and 1.2–1.5 for K in comparison with the dead bacterium inoculated controls. In addition, extracellular polysaccharide production by the bacterium increased with time but the bacterium produced small pH changes (6.0–6.5) in the course of mineral dissolution experiment. The bacterium was found to produce siderophores and have the characteristics of acid or alkali and salt tolerance and temperature resistance. The result suggested that feldspar and biotite dissolution may be mainly caused by extracellular polysaccharide and/or siderophores produced by the bacterium.     

土壤中钾细菌的筛选及筛选底物加入量对其数量的影响

研究土壤中加入不同数量的钾长石粉后其解钾细菌数量的变化,同时初步筛选钾细菌,为进一步研究土壤中解钾细菌的分离、筛选及其鉴定提供参考。测试土壤中加入不同数量的钾长石粉后其解钾细菌数量,对结果进行比较分析;利用四苯硼钠法测试菌株解钾能力,并进行初步筛选。结果表明,按钾细菌数量由多到少的顺序,筛选底物加入量为0.2%0.1%0.4%空白对照;筛选菌株的解钾效率高于K01的共14株,高于K02的共9株。解钾效率最高的菌株5.15-2解钾效率为35.4%,较外购生产菌种K01高13倍,与本实验室保存菌种K02相比高3.6倍。     

Feldspar Tunneling by Fungi along Natural Productivity Gradients

Recently, it was hypothesized that ectomycorrhizas hyphae are involved in mineral tunneling. We evaluated the role of ectomycorrhizas in mineral weathering and the ecosystem influx of basic cations by correlating mineral tunnel density to ectomycorrhizas density in two forest productivity gradients. The gradients, two gentle slopes in northern Sweden, are the result of groundwater movement and are characterized by reduced productivity upslope due to lower nitrogen availability. As expected, ectomycorrhizas density in the O horizon was higher upslope, where nitrogen availability was lower and where the vegetation was dominated by ectomycorrhizas plant species. We consistently found that tunnel formation in mineral grains was more intense in nutrient-poor sites, indicating a higher contribution of fungi to ecosystem influx of potassium and calcium. ectomycorrhizas density was positively correlated with feldspar tunnel density in the upper 2 cm of the E horizon. This suggests that ectomycorrhizas are involved in mineral tunneling. We discuss the possible involvement of ericoid mycorrhizas and saprotrophic fungi in feldspar tunneling and the role of the weathering status of mineral grains as additional factors controlling mineral funneling.     

Adsorption isotherms of lanthanum to soil constituents and effects of pH,EDTA and fulvic acid on adsorption of lanthanum onto goethite and humic acid

Abstract

La³⁺ adsorption isotherms to five soil constituents (quartz, feldspar, kaolinite, goethite and humic acid) are studied. EDTA, fulvic acid and pH effects are also investigated on the adsorption of lanthanum by goethite and humic acid because of their relative importance in affecting metal environmental behavior. Adsorption isotherms of La³⁺ to five constituents show differences in adsorption capacity and in shape in the studied range of La³⁺. These constituents can be classified according to their adsorption capacity: humic acid > goethite ≈ kaolinite > feldspar ≈ quartz. pH increase could promote humic acid and goethite adsorption of La³⁺ while EDTA could reduce the adsorption by these two adsorbents. Fulvic acid can reduce humic acid adsorption but has less effect on adsorption by goethite.     

An RNA-Sequencing Study of the Genes and Metabolic Pathways Involved in Aspergillus niger Weathering of Potassium Feldspar

Microbial transformation of potassium feldspar to produce organic composite potassium fertilizer is recognized to be an important method of effective use of the huge reserves of low grade K⁺-bearing rock in China. The mechanism underlying microbial weathering of silicate minerals is still unclear, and this is an obstacle to practical methods of application. To thoroughly understand the molecular mechanism responsible for the weathering of potassium feldspar by Aspergillus niger at a molecular level, high-throughput RNA-sequencing (RNA-seq) and treatment with different potassium sources (cultured in Czapek medium with soluble K⁺ or potassium feldspar) were used to investigate the differentially expressed genes of A. niger associated with potassium feldspar weathering and the related metabolic pathways. A series of differentially expressed genes related to the synthesis and transportation of organic acids, polysaccharides, and proteins (enzymes) were found to be closely associated with the K⁺ released from minerals through bioinformatic analysis. In addition, 12 genes that showed apparent expression differences by RNA-seq analysis and are relevant to organic acid synthesis, protein modification, maintenance of cellular homeostasis, and material transportation, were selected to be further verified using RT-qPCR. Compared to the fungal samples cultured with soluble K⁺, those with potassium feldspar have certain genes that are more up-regulated, such as the genes for Na⁺,K⁺-ATPase (447.6 multiples), cystathionine beta-synthase (5.6 multiples), cysteine synthase (9 multiples), and glutathione synthase (3.5 multiples). The analysis indicates that A. niger weathering of potassium feldspar is due to the synergistic effect of many factors including the up-regulation of certain genes and activation of related metabolite pathways. The research improves our understanding of the mechanisms of microbial weathering of silicate minerals.     

土壤中解钾菌K02的筛选、鉴定及培养条件优化

解钾微生物是能够在土壤或纯培养条件下,将含钾矿物如长石、云母等不能被作物吸收利用的矿物态钾分解,并产生水溶性钾的微生物。利用以钾长石粉为唯一钾源的硅酸盐细菌选择性培养基,采用梯度稀释分离法平板划线对番茄土壤中的钾细菌进行筛选。利用原子吸收火焰分光光度法测定钾细菌培养液中可溶性钾的含量,筛选高效解钾菌株。通过形态观察和16S rDNA序列GenBank比对,同时利用clustalx和MEGA 4.0等相关软件构建系统进化树对解钾能力最强的菌株K02进行鉴定,初步鉴定该解钾菌为胶质类芽胞杆菌(Paenibacillus mucilaginosus);利用单因素试验法对K02菌株培养基组分及发酵条件进行优化,初步确定菌株K02最佳培养基组分以解钾复筛培养基为基础,其碳源、氮源及无机盐以可溶性淀粉1%、酵母膏0.2%、K_2HPO_40.05%为最佳;菌株K02最佳发酵条件:培养温度为30℃,培养时间为48 h,培养基装量为50 mL/250 mL,培养基初始pH值为7.5,接菌量为5%,这一结果为解钾菌肥的研制和生产提供参考。