Location and stability of a recombinant ovine prion protein in synthetic humic like-mineral-complexes

Location and stability of a recombinant prion protein (recPrP) and its interaction with humic-like complexes were investigated by low-temperature ashing (LTA), thermal gravimetric (TG), and scanning electron microscopy (SEM) analyses. Humic-like complexes were obtained by abiotic polymerization of catechol, one of the possible precursors of soil humic matter, through the catalysis of birnessite, a manganese oxide common in soil environment. The recPrP was immobilized in organomineral complexes via sorption or entrapment. Complexes were treated by LTA, allowing the controlled removal of organic matter layer by layer, from the external to the internal side, with minimal disturbance of mineral constituents. Thermal gravimetric and SEM analyses were performed on specimens before and after LTA treatment. Entrapped recPrP, compared with sorbed, resulted less easily accessible to LTA treatment and showed a higher thermal stability by TGA analyses. On the basis of these findings, we hypothesize that the processes leading to newly formed organic complexes can enhance prion stability in soil and thus influence the environmental diffusion of infectivity

Effects of cyanobacteria strains selected for their bioconditioning and biofertilization potential on maize dry matter and soil nitrogen status in a South African soil

Some cyanobacteria strains have biofertilization and/or bioconditioning effects in soils as a result of their ability to fix dinitrogen or produce exocellular polysaccharides. The objective of the present study was to screen indigenous cyanobacteria strains with the potential to improve the N fertility and structural stability of degraded soils, and evaluate their ameliorative effectiveness in semiarid soils of the Eastern Cape, South Africa. Soils from Guquka, Hertzog and Qunu villages, and Fort Cox College were used in the screening study. The results showed that only three cyanobacteria strains (3g, 3v and 7e) out of 97 isolated strains were heterocystous, with appreciable nitrogenase activity and the ability to produce exocellular polysaccharides. Nostoc strains 3g and 3v had a greater ability to produce exocellular polysaccharides, but low potential to fix dinitrogen (4.7 and 1.3 nmol C2H4 μg-1 chl h-1, respectively). Strain 7e had the greatest ability to fix dinitrogen (16.1 nmol C2H4 μg-1 chl h-1), but produced fewer exocellular polysaccharides. The ability of strains 3g and 7e to influence maize dry matter (DM) and soil C and N contents was tested in a nitrogen-poor soil with Nostoc strain 9v as a reference strain. Potted soils with and without growing maize plants were inoculated with the different cyanobacteria strains in a glasshouse at a rate of 6 g m-2 soon after maize emergence. Harvesting and soil sampling were done 6 weeks after inoculation. Inoculation with strains 3g and 7e increased maize DM and N uptake significantly, on par with the reference strain. These increases were consistent with increases in nitrate-N observed at harvest time in inoculated cropped and non-cropped soils. Strain 7e resulted in greater increases in soil nitrate-N, tissue N and uptake than strain 3g, perhaps because of its greater ability to fix dinitrogen. Cropping with maize reduced soil total C and N, possibly owing to its negative effects on cyanobacteria establishment. These results suggest that indigenous cyanobacteria strains screened for greater N2-fixing ability have the potential to improve the productivity of N-poor soils in semiarid regions in South Africa. © 2010 Japanese Society of Soil Science and Plant Nutrition.This work was part of a European Union INCO-DEV funded research programme in Southern Africa (CYANOSOILS), Project ICA4-CT-2001-10058. The National Research Foundation of South Africa granted a fellowship to the first author to undertake the study at the University of Fort Hare. We thank Antonia Herrero and José Enrique Frías of Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas, Sevilla, Spain, for their assistance with the isolation and characterization of the cyanobacteria strains

An assessment of soil fertility and agronomic constraints in southern African Savannas: A case study of the Pandamatenga area, Botswana

Pandamatenga is one of parts of Botswana most suited to dryland farming. The major constraint to crop production is the lack of adequate rainfall. Pellic vertisols (dark cracking clay soils) and ferralic arenosols developed on Kalahari sands constitute the main soil formations. Pandamatenga vertisols are moderately fertile while ferralic arenosols have a very low inherent physical and chemical fertility. This paper reports on the physical and chemical properties of these soils and the characteristics of their organic matter. Some agronomic strategies aimed at their sustainable use are also considered

Nostoc cyanobacterial inoculation in South African agricultural soils enhances soil structure, fertility, and maize growth

13 pages, figures, and tables statistics.Many soils in South Africa have low nutrient supply, poor structural stability and are prone to soil erosion due to susceptibility to surface sealing and crusting. Two crusting soils from the Eastern Cape Province, South Africa were used to evaluate the effects of inoculation with a strain of Nostoc on soil structure, fertility and maize growth. The Nostoc suspension was uniformly applied over potted soils at a rate of 6g (dry weight) per square meter soon after maize germination. Nostoc inoculation increased soil N by 17% and 40% in Hertzog and Guquka soils, respectively. Soil C was also increased significantly and this increase was strongly associated with that of soil N (R2 = 0.838). The highest contents of soil C, soil N and mineral N, however, were found in non-cropped Nostoc inoculated soils. Nostoc inoculation increased maize dry matter yields by 49% and 40% in Hertzog and Guquka soils, respectively. Corresponding increases in maize tissue N were 23% and 14%, respectively. Scanning electron microscopy (SEM) revealed that soil particles and fragments of non-cropped inoculated soils had coatings of extracellular polymeric substances (EPS) with other particles enmeshed in networks of filaments, whilst by contrast little or no EPS and/or filaments were observed on cropped and/or non-inoculated soils. This was consistent with chemical analysis which showed that Nostoc caused significant increases in the EPS and soil C contents of non-cropped soils. The proportion of very stable aggregates was increased by inoculation with Nostoc possibly due to the greater quantities of soil C and EPS observed in inoculated soils. Inoculated soils cropped with maize had a lower proportion of stable aggregates presumably due to their low soil C and EPS contents compared to non-cropped soils. The results suggested that Nostoc could improve the fertility and structural stability of the studied degraded soils.This work was part of an EU, INCODEV funded research programme in Southern Africa (Cyanosoils), Project ICA4-CT-2001-10058.Peer reviewe