Differences in potassium forms between cutans and adjacent soil matrix in a Grey Clay Soil

International audienceCutans are common fabric features in soil and represent foci of chemical and biological reactions. The influence of cutans on potassium forms and their transformations were investigated for a Western Australian grey clay soil. Cutans and matrix soil had similar clay mineral associations with kaolinite, smectite and illite being present, but had different chemical properties. The organic carbon content of cutans was higher than for matrix soil, while pH values and oxalate extractable/dithionate extractable iron (Feo/Fed) ratios were lower. Numerous SEM-EDS single point analyses of cutans and the plasma phase of the matrix soil indicated that the mean value of K concentration in cutans is greater than in matrix soil, and that the K concentration decreased with distance from cutan to matrix. Chemical extractions showed mean values of total K and latent exchangeable K were higher for cutans than for matrix soil, but both fixed K and exchangeable K values were the same for cutans and matrix soil. In a K adsorption/desorption experiment, 35% of K adsorbed by matrix soil could not be desorbed by 1 M NH4Ac. These results indicate that cutans are relatively enriched in K and may play an important role in determining available K and latent exchangeable K due to the special physical and chemical environments they provide in the soil

Microporosity of BIF hosted massive hematite ore, Iron Quadrangle, Brazil.

Massive hematite ore (MHO) is a special high-grade iron ore, used as lump ore in the process of obtaining direct reduction iron (DRI). The influence of porosity on the reducibility of MHO from the Capitão do Mato Mine (Iron Quadrangle, Brazil) was investigated using optical and scanning electron microscopes on drill core and open pit samples. Hematite is the main component of the samples and occurs as granular crystals (10 mum), microplates (1 mum) and euhedral martite (10 to 30 mum). Quartz, maghemite, kenomagnetite and goethite are minor components. Primary micropores (Å to 1 mum) are associated with microplaty crystals that fill cavities between granular hematite. Secondary micropores (Å to 5 mum) related to euhedral martite crystals, are the most important. The total porosity of weathered samples, measured using nitrogen adsorption and mercury injection, attains values up to 11%, whereas unweathered samples have a porosity less than 2.5%. Reducibility is strongly enhanced by porosity, but inhibited by structure (bedding)

Estimation des propriétés de rétention en eau des sols : Utilisation de classes de pédotransfert après stratifications texturale et texturo-structurale

Un programme de mesures des propriétés de rétention en eau des sols a été développé par l'INRA depuis une dizaine d'années afin de constituer un jeu de données qui puisse être utilisé pour tester les fonctions de pédotransfert (FPT) qui ont été proposées dans la littérature, en établir de nouvelles si celles proposées se révèlent non satisfaisantes et dans ce dernier cas, tester les nouvelles FPT. Dans ce contexte général et partant du constat que les FPT proposées ne permettent pas de prédire les propriétés de rétention en eau de façon satisfaisante, cette étude se propose de suivre une autre voie que celle habituellement suivie pour établir un outil d'estimation des propriétés de rétention en eau. Des classes de pédotransfert (CPT) sont proposées par classe de texture ou par classe combinant texture et structure, cette dernière étant renseignée à l'aide de la densité apparente déterminée sur des mottes de dimensions centimétriques. Ainsi, en utilisant soit la texture seule, soit la texture et la densité apparente de motte, on dispose des teneurs en eau massiques à –10, –33, –100, –330, –1000, –3 300 et –15 000 hPa en fonction de l'appartenance de l'horizon à telle ou telle classe de texture ou, telle ou telle classe combinant texture et densité apparente de motte. La qualité de la prédiction a été testée sur un échantillon de validation ; elle a aussi été comparée à celle qui aurait été obtenue si l'on avait utilisé les CPT de Jamagne et al. (1977). Par rapport à ces CPT, les résultats montrent une importante réduction du biais et un accroissement de la précision lorsque l'on utilise les CPT par classe de texture proposées dans cette étude. Lorsque l'on compare les CPT par classes texturales aux CPT par classes texturo-structurales, il n'y a pas d'amélioration notable du biais mais celui-ci était déjà très faible avec les CPT par classes texturales. En revanche, les CPT par classes texturo-structurales, qui permettent de tenir compte à la fois de la texture et de l'état structural du sol, améliorent la précision des prédictions. Pour les CPT par classes texturales, des teneurs en eau volumiques sont déduites des teneurs en eau massiques en utilisant la densité apparente de l'horizon. Les paramètres du modèle de van Genuchten sont donnés pour chaque classe de CPT. Une démarche permettant de prédire les propriétés de rétention en eau d'un horizon est proposée

Estrutura e propriedades hidráulicas em latossolos sob cultivo na região do Cerrado.

Na região do Cerrado, o potencial produtivo dos solos apresenta-se cada vez mais degradado devido à utilização de sistemas agrícolas extrativistas. Neste contexto, os Latossolos, que cobrem cerca de 50% da superfície do Cerrado, constituem um modelo bastante sensível. Suas propriedades químicas e físicas podem ser rapidamente transformadas pela utilização de práticas agrícolas inadequadas. As alterações na fertilidade química devido à utilização agrícola do solo são conhecidas, mas o mesmo não ocorre no que se concerne à fertilidade física. Na realidade, uma análise detalhada da literatura mostra que a diminuição da fertilidade global após a utilização do solo é atualmente perceptível na maioria dos agroecossistemas, mas a evolução das propriedades físicas é menos evidente. Os estudos revelam que a utilização do solo é acompanhada de uma importante e rápida evolução da sua porosidade em superfície, que se traduz freqüentemente por um aumento da massa volumétrica do solo, a qual sob vegetação natural apresenta valores baixos, particularmente nos Latossolos argilosos. Observa-se, também, diminuição da estabilidade estrutural, aumento do teor de argila dispersa em água, aumento da resistência à penetração e diminuição da condutividade hidráulica.bitstream/CNPAF/21730/1/bolpesq_8.pd

Lactobacillus johnsonii La1 antagonizes Giardia intestinalis in vivo

This study describes the in vivo activity of Lactobacillus johnsonii La1 (NCC533) in Giardia intestinalis-infected gerbils (Meriones unguiculatus). Daily administration of lactobacilli in the drinking water from 7 days before inoculation with Giardia trophozoites efficiently prevented G. intestinalis strain WB clone C6 from infecting gerbils. More specifically, shedding of fecal Giardia antigens (GSA65 protein) was diminished in the La1-treated group, and resolution of infection was observed by 21 days postinoculation. Histology and analysis of enzymatic markers of microvillus membrane integrity revealed that probiotic administration also protected against parasite-induced mucosal damage. In addition, a cellular response to Giardia antigens was stimulated in spleen cells from La1-treated gerbils. Results show for the first time the antigiardial effect of probiotic lactobacilli in vivo and provide further insight into the antagonistic properties of lactic acid bacteria against protozoa involved in intestinal infections.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Criotecnología de Alimento

The conserved C-terminus of the PcrA/UvrD helicase interacts directly with RNA polymerase

Copyright: © 2013 Gwynn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by a Wellcome Trust project grant to MD (Reference: 077368), an ERC starting grant to MD (Acronym: SM-DNA-REPAIR) and a BBSRC project grant to PM, NS and MD (Reference: BB/I003142/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Tn1546 is part of a larger plasmid-encoded genetic unit horizontally disseminated among clonal Enterococcus faecium lineages

o determine the genetic composition of the first VanA-type plasmid (pIP816) reported, which was isolated from a clinical Enterococcus faecium (BM4147) strain in France in 1986, and to reveal the genetic units responsible for the dissemination of the vanA gene cluster by comparisons with current, published and additionally generated vanA-spanning plasmid sequences obtained from a heterogeneous E. faecium strain collection (n = 28).Plasmid sequences were produced by shotgun sequencing using ABI dye chemistry and primer walking, and were subsequently annotated. Comparative sequence analysis of the vanA region was done with published plasmids, with a partial vanA plasmid (pVEF4) reported here and to >140 kb of sequence obtained from a collection of vanA-harbouring plasmid fragments. Bioinformatic analyses revealed that pIP816 from 1986 and contemporary vanA plasmids shared a conserved genetic fragment of 25 kb, spanning the 10.85 kb vanA cluster encoded by Tn1546, and that the larger unit is present in both clinical and animal complexes of E. faecium. A new group II intron in pVEF4 was characterized. Comparative DNA analyses suggest that Tn1546 disseminates in and between clonal complexes of E. faecium as part of a larger genetic unit, possibly as a composite transposon flanked by IS1216 elements

Lactobacillus johnsonii La1 antagonizes Giardia intestinalis in vivo

This study describes the in vivo activity of Lactobacillus johnsonii La1 (NCC533) in Giardia intestinalis-infected gerbils (Meriones unguiculatus). Daily administration of lactobacilli in the drinking water from 7 days before inoculation with Giardia trophozoites efficiently prevented G. intestinalis strain WB clone C6 from infecting gerbils. More specifically, shedding of fecal Giardia antigens (GSA65 protein) was diminished in the La1-treated group, and resolution of infection was observed by 21 days postinoculation. Histology and analysis of enzymatic markers of microvillus membrane integrity revealed that probiotic administration also protected against parasite-induced mucosal damage. In addition, a cellular response to Giardia antigens was stimulated in spleen cells from La1-treated gerbils. Results show for the first time the antigiardial effect of probiotic lactobacilli in vivo and provide further insight into the antagonistic properties of lactic acid bacteria against protozoa involved in intestinal infections.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Criotecnología de Alimento

Classification and evolutionary history of the single-strand annealing proteins, RecT, Redβ, ERF and RAD52

BACKGROUND: The DNA single-strand annealing proteins (SSAPs), such as RecT, Redβ, ERF and Rad52, function in RecA-dependent and RecA-independent DNA recombination pathways. Recently, they have been shown to form similar helical quaternary superstructures. However, despite the functional similarities between these diverse SSAPs, their actual evolutionary affinities are poorly understood. RESULTS: Using sensitive computational sequence analysis, we show that the RecT and Redβ proteins, along with several other bacterial proteins, form a distinct superfamily. The ERF and Rad52 families show no direct evolutionary relationship to these proteins and define novel superfamilies of their own. We identify several previously unknown members of each of these superfamilies and also report, for the first time, bacterial and viral homologs of Rad52. Additionally, we predict the presence of aberrant HhH modules in RAD52 that are likely to be involved in DNA-binding. Using the contextual information obtained from the analysis of gene neighborhoods, we provide evidence of the interaction of the bacterial members of each of these SSAP superfamilies with a similar set of DNA repair/recombination protein. These include different nucleases or Holliday junction resolvases, the ABC ATPase SbcC and the single-strand-binding protein. We also present evidence of independent assembly of some of the predicted operons encoding SSAPs and in situ displacement of functionally similar genes. CONCLUSIONS: There are three evolutionarily distinct superfamilies of SSAPs, namely the RecT/Redβ, ERF, and RAD52, that have different sequence conservation patterns and predicted folds. All these SSAPs appear to be primarily of bacteriophage origin and have been acquired by numerous phylogenetically distant cellular genomes. They generally occur in predicted operons encoding one or more of a set of conserved DNA recombination proteins that appear to be the principal functional partners of the SSAPs