Influence of soil properties on the vertical movement of genetically-marked Pseudomonas fluorescens through large soil microcosms

Summary Vertical translocation of the introduced transposon Tn5-tagged Pseudomonas fluorescens cells was studies after irrigation of 50-cm long soil columns of loamy sand. The soil in the columns was slowly brought to saturation using groundwater, and enough water was then slowly added to permit collection of the percolated water. Introduced bacteria were transported to lower soil layers to a significantly higher degree in undisturbed soil cores than in repacked cores; water transport was hampered in both core types due to high soil bulk densities. Soil bulk density affected the degree of transport of the introduced cells; progressively more cells were translocated to deeper soil layers and into the percolation water at decreasing soil bulk densities. Repeated percolation of soil at a bulk density of 1.25 caused an increase in Tn5-tagged cell numbers in the lower soil layers and in the percolated water. Further, cells initially introduced into a dry (5.3% moisture) soil were translocated to a lesser extent than cells introduced into a wetter (13% moisture) soil. Finally, wheat roots enhanced the water-induced transport of introduced cells to the 40- and 50-cm deep soil layers and into the effluent, but not to the remaining soil layers. Large soil columns such as those used in the present study are useful in assessing the transport and survival of introduced bacterial cells in soils under a variety of simulated environmental conditions.     

Effect of Arbuscular Mycorrhizal Fungi and Phosphate-Solubilizing Bacteria Consortia Associated with Phospho-Compost on Phosphorus Solubilization and Growth of Tomato Seedlings (Solanum lycopersicum L.)

ABSTRACT

The exploitation of phosphate mines generates an important quantity of phosphate sludge that remains accumulated and not valorized. In this context, composting with organic matter and rhizospheric microorganisms offers an interesting alternative and that is more sustainable for agriculture. This work aims to investigate the synergetic effect of arbuscular mycorrhizal fungi (AMF), phosphate-solubilizing bacteria (PSB) and phospho-compost (PC), produced from phosphate-laundered sludge and organic wastes, and their combination on plant growth, phosphorus solubilization and phosphatase activities (alkaline and acid). Inoculated mycorrhizae and bacteria strains used in this study were selected from plant rhizosphere grown on phosphate-laundered sludge. Significant (p < .05) increases in plant growth was observed when inoculated with both consortia and PC (PC+ PSB+ AMF) similar to those recorded in plants amended with chemical fertilizer. Tripartite inoculated tomato had a significantly (p < .05) higher shoot height; shoot and root dry weight, root colonization and available P content, than the control. Co-inoculation with PC and AMF greatly increased alkaline phosphatase activity and the rate of mycorrhizal intensity. We conclude that PC and endophytic AMF and PSB consortia contribute to a tripartite inoculation in tomato seedlings and are coordinately involved in plant growth and phosphorus solubilization. These results open up promising prospects for using formulate phospho-compost enriched with phosphorus-solubilizing microorganisms (PSM) in crop cultivation as biofertilizers to solve problems of phosphate-laundered sludge accumulation.     

Characterization of brushite as a re-crystallization product formed during bacterial solubilization of hydroxyapatite in batch cultures

Two strains of bacteria (Burkholderia sp., strain FeGL01, and Burkholderia caribiensis, strain FeGL03) were isolated from a Brazilian high phosphorus iron ore. The capacity of both strains to solubilize hydroxyapatite, Ca₅(PO₄)₃(OH), was assessed in plate and batch cultures. In batch cultures, the concentration of solution-P showed two kinetics: an initial one, characterized by a continuously increasing kinetics and a second one, characterized by oscillatory kinetics. To understand the nature of these oscillations, phosphatic residues in the spent broth were collected before, during and after the oscillations, and characterized using scanning electron microscopy (SEM), energy-dispersive X-ray chemical microanalyses (EDX) and X-ray diffraction (XRD). From these studies, it was found that drops in P concentration were related to the formation of an intermediate phosphate in the residues, identified as brushite, CaHPO₄·2H₂O. Later increase of available P in the solution was found to be a consequence of re-dissolution of brushite crystals previously formed. Re-crystallization of brushite was also detected in plate cultures after 12-14 days of incubation     

羽毛蛋白粉高效利用研究

采用物理加工与生物加工结合的方法，即先超微粉碎至微米级后再用解朊酶进行体外水解处理的方法对羽毛粉进行饲料化研究，通过研究发现经处理的羽毛粉比对照组（未经处理过的羽毛粉）的可溶性蛋白质含量和溶解度分别比原来增加了3.37倍和3.38倍，胃蛋白酶消化率提高了15%，表明此加工工艺可大大提高羽毛粉的生物学效价。     

Evolution of humic substances from unripe compost during incubation with lignolytic or cellulolytic microorganisms and effects on the lettuce growth promotion mediated byAzotobacter chroococcum

Some recalcitrant organic wastes, which contain a large proportion of lignin or cellulose, are not changed much by composting, and thus the effectiveness of the compost as fertilizer is usua.lly low. In this study, incubation of unripe compost with ligno-cellulolytic microorganisms —Trichoderma viride orBacillus spp. — was investigated to increase the degree of humification of the organic matter present, and improve ils quality as a soil amendment. High-performance liquid chromatography (HPLC) analyses together with humification indices and electrofocusing patterns were used to monitor the evolution of the humic substances during the incubation process. Plant growth effects exerted by Azotobacter chroococcum on lettuce plants growing on the previously incubated compost were affected by the length of incubation and by changes in the composition of humic substances. Higher organic matter content and better humification seem to be important factors for predictingA. chroococcum hebaviour in the rhizosphere.     

Methods for the investigation of metabolic activities and shifts in the microbial community in a soil treated with a fungicide

Samples from a sandy agricultural soil were treated with increasing amounts of a fungicide (Sportak). The effects on the soil microflora were investigated over several weeks by monitoring basal and substrate-induced respiration and basal and substrate-induced heat output. The microbial biomass, metabolic quotient (qCO₂), relative heat output (rqheat), lag phase of substrate use, and calorimetric: respirometric ratio were used as ecophysiological parametèrs. As structural and community-specific parameters, we recorded tryptophan contents and auxin metabolism, and calculated the ratios of fungal to bacterial respiration by antibiotic inhibition of substrate-induced respiration. Sportak either inhibited or stimulated the microbiota, depending on the length of exposure to the fungicide and the amount applied. Mineralization of dead biomass was reflected in increased soil tryptophan contents after the Sportak application. A shortened lag phase demonstrated inhibition and a prolonged lag phase stimulation of substrate use. This changed with the experimental phase. The rqheat and the calorimetric: respirometric ratio proved to be suitable parameters for the detection of stress metabolism (repair processes) in soil microbiota, because thermodynamic processes and catabolic and anabolic metabolism are taken into account at the same time. Following the application of Sportak, indole 3-acetic acid biosynthesis decreased while indole-3-ethanol biosynthesis increased, probably as a result of a transitional community shift from K-strategists towards r-strategists. It was not the fungicide but the formulation (mainly xylol) that damaged the organisms. A shift in the ratio of fungi to bacteria was also observed, suggesting that the bacteria were probably more sensitive to xylol than the fungi.     

Microbial and enzyme activity in soils amended with a natural source of easily available carbon

The addition of sugar beet to soils as a source of C led to an increase in the availability of easily utilizable C (glucose), which in turn markedly increased numbers of soil bacteria and of the yeast Williopsis californica. Nitrification, P solubilization, urea hydrolysis (and the subsequent nitrification of liberated NH _inf4 ^sup+ ) were stimulated by this amendment. The stimulation of nitrification may have been a result of increased heterotrophic nitrification. In contrast, the concentration of sulphate in S^o-amended soils declined following amendment, presumably as the result of enhanced S immobilization. Activity of the enzymes amylase, aryl sulphatase, invertase, phosphatase, dehydrogenase, and urease were all stimulated by the sugar beet amendment. These results suggest that sugar beet amendment could be used to increase the rate of release of plant-available ions from fertilizers such as insoluble phosphates. Problems may arise, however, from a subsequent increase in nitrification and reduced sulphate availability.     

新型生物制剂“易丰收”对大豆产量促生效应及根际微生物影响研究

通过大豆‘辽豆20’盆栽试验,研究新型生物制剂“易丰收”对大豆的促生效应以及对根际微生物的影响,并结合芸薹素内酯、复合肥料与其进行对比。此文调查了大豆株高、茎粗、根瘤数等生长指标以及产量构成因素,另外还有根际细菌、放线菌和真菌数量。通过SPSS 13.0统计软件分析数据,可以得出结论。“易丰收”较之芸薹素内酯,更能明显促进大豆的生长发育和产量,显著提高大豆根瘤数量,增加根际细菌数量,尤其配合肥料效果更好。     

氟磺胺草醚降解菌的分离鉴定及生长特性研究

氟磺胺草醚广泛应用于大豆田防除阔叶杂草,其长残留问题十分严重,微生物降解是解决氟磺胺草醚残留问题的有效途径。利用高压富集的方法,从长期施用氟磺胺草醚的田间土壤中,分离筛选出6株能够以氟磺胺草醚为唯一碳源生长的降解菌,其中一个菌株在查氏液体培养基中培养5d,对40mg a.i./L氟磺胺草醚的降解率为92.13%。通过形态特征鉴定并对该菌株18S rRNA的部分序列进行基因测序,对其在系统发育分类学上的地位加以分析,同时研究环境条件对其生长的影响。结果表明,该菌株为真菌,初步鉴定为黄曲霉(Aspergillus flavus),实验室命名为TZ1985。菌株TZ1985最适生长温度为25℃,最适培养基pH值为7.0,生长最适葡萄糖含量为0.6%,生长最适氟磺胺草醚的浓度是10mg a.i./L。     

养猪场粪污水生物处理工艺技术研究

通过对粪污水进行分离、沉淀、曝气、生物滤池和添加微生物菌群有机物的降解对比试验，优选出了一套工艺流程，并在北京东广德猪场进行了工程实践。结果表明，优选出的以生物滤池为主的好氧生物处理工艺降解效率高、设备投资少、运行费用低且管理方便。高速生物滤池的降解率可达90％以上，整个污水处理系统有机物的降解率达到93%～97％。从系统运行水质监测结果来看，在保证粪污水全面实现达标排放和猪粪(渣)无害化处理的前提下，这种处理工艺将各个单一处理技术有机地结合起来，形成一种综合处理与利用的系统工程，达到经济、社会、生态效益的高度统一。