Native Chromium Resistant Staphylococci Species from a Fly Ash Dumping Site in South Africa Harbor Plasmid pMOL28 Determinants

Sixty-six chromium-resistant Staphylococci species belonging to S. epidermidis, S. aureus, S. saprophyticus and S. arlettae were previously isolated from a chromium-polluted Fly ash (FA) dumping site in South Africa. However the genetic mechanisms responsible for chromium resistance were not known. Polymerase chain reaction and DNA-DNA hybridization techniques were used to explore whether or not these staphylococcal strains exhibited chr determinants of plasmid pMOL28 that confers chromate resistance to Cupriavidus metallidurans. Genes ChrB1 and ChrC were found to be present in the genomes of all the Staphylococci species. However, gene ChrA1 was shown to be present only in the genome of S. aureus. These results showed that Chr genes could be distributed from Cupriavidus metallidurans (Gram negative bacteria) to Staphylococci species (Gram positive bacteria), probably by horizontal transfer. Soixante-six Staphylococci résistants au chrome appartenant aux espèces: S. epidermidis, S. aureus, S. saprophyticus et S. arlettae ont été préalablement isolés d'un site d'enfouissement de cendres volantes pollué au chrome en Afrique du Sud. Les mécanismes génétiques responsables de la résistance au chrome chez ces bactéries n'étant pas connus, des méthodes utilisant la PCR et des techniques d'hybridation ADNADN ont été utilisées pour voir si oui ou non ces souches de staphylocoques arboraient les déterminants chr du plasmide pMOL28 qui confère la résistance au chrome chez Cupriavidus metallidurans. Par utilisation de ces techniques, il a été montré que les gènes ChrB1 et ChrC sont présents dans les génomes de toutes les espèces de Staphylococci. Cependant, la présence du gène ChrA1 a été mise en évidence que dans le génome de S. aureus. Ces résultats montrent que les gènes Chr pourraient être distribués à partir de Cupriavidus metallidurans (bactérie à Gram négatif) jusqu'aux espèces de staphylocoques (bactéries à Gram positif), probablement par transfert horizontal.Mots clés: Cendres volantes, bactéries résistantes au chrome, Staphylococci, déterminant Chr, pMOL2

Impact des proprietes physicochimiques des sols de culture du manioc sur l’abondance et la diversite des communautes de champignons mycorhiziens à arbuscules dans la zone agroecologique d’azaguie, Sud-Est de la Côte D’Ivoire

En Côte d’ Ivoire, la baissede la fertilité des terres de culture du manioc,  est à l’origine des rendements faibles. L’utilisation de l’effet bénéfique des  champignons mycorhiziens arbusculaires (CMA) pourrait améliorer  durablement ces rendements. Ce travail a pour but de mettre en évidence l’écologie, la diversité et la structuration des communautés de CMA  endogènes associés à la culture du manioc dans les sols de la zone  agroécologique d’Azaguié. Les études ont été menées à partir des sols de champs de manioc (Ahoua 1, Ahoua 2, Mbromé 1, Mbromé 2). Ces sols étaient très acides (pH inférieurs à 5,17), pauvres en bases échangeables (CEC inférieures à 17,1 cmol/kg), en phosphore assimilable (P.  assimilable inférieur à 30,71 ppm) et en matière organique. Il a été  dénombré 44 espèces de CMA reparties en treize genres. Les genres  Glomus (55,17 %) et Acaulospora (30,14 %) sont les plus abondants. Les densités des spores de CMA, sont inférieures à 14,68 spores.g-1. La proportion moyenne de spores non-viables (55 %) est élevée. Il a été noté des corrélations positives entre les communautés de CMA et le  magnésium (R = 0,65), la CEC (R = 0,69), l'argile (R = 0,74) et le limon grossier (R = 0,79). Par contre des corrélations négatives ont été obtenues avec le sable fin (R = -0,60) et le sable grossier (R = -0,59).Mots clés : Manioc, Azaguié, Côte d’Ivoire, champignons mycorhiziens à arbuscules.INFLUENCE OF CASSAVA SOILS PHYSICOCHEMICAL PROPERTIES ONTHE ABUNDANCE AND DIVERSITYOF ARBUSCULAR MYCORRIZAL FUNGI  COMMUNITIES’ IN AZAGUIÉ AGROECOLOGICAL AREA, SOUTH-EAST CÔTE D’IVOIREIn Côte d’Ivoire, the decline in cassava soil fertility is causing low yields. The use of the beneficial effect of arbuscular mycorrhizal fungi (AMF) can sustainably improve the yields. The aim of this study was to highlight the ecology, diversity and community structure of endogenous CMA associated with cassava. The studies were conducted using cassava field soils (Ahoua 1 Ahoua 2 Mbromé 1 Mbromé 2). These soils were very acidic (pH less than 5.17), with low exchangeable bases capacities values (CEC less than 17.1 cmol / kg), low available phosphorus levels (available P less than 30.71 ppm) and poor organic matter proportions. Thirteen AMF genera comprising 44 species were identified. The genera Glomus (55.17 %) and Acaulospora (30.14 %) were the most abundant. AMF spores densities were (8.42 and 14.68 spores.g-1). The proportion of non-healthy spores was 55 %. There were positive correlations between AMF communities and magnesium (R = 0.65 and 0.59), CEC (R = 0.69), clay (R = 0.74) and coarse silt (R = 0.79) and negative correlations were obtained with fine sand (R = -0.60) and coarse sand (R = -0.59).Key words : Cassava, Azaguié Côte d’Ivoire, abuscular mycorrhiral fungi

Mechanically tunable metasurface with large gamut of color: Lateral hybrid system

Hybrid metasurfaces are made of metals and dielectrics in which dielectrics (metals) are sandwiched between metals (dielectrics) to control the reflection and transmission of light. The existing designs have low sensitivity, little color coverage, and a lack of flexibility. Here, a new structural color design is proposed in which metals and dielectric resonators are arranged spatially in 2D to form a lateral hybrid system, instead of being placed as layers. Such a design exhibits a high level of sensitivity to mechanical forces because it works via 2D optical coupling and light confinement between adjacent resonators. Our study shows that in-planar coupling of two dissimilar resonators can enhance sensitivity by an order of magnitude in comparison to stacking them. Metasurfaces with our design would have unprecedented mechanical tunability without compromising either the materials choice or processing. Using the proposed hybrid system, we demonstrate large tunability across the full range of colors with only a 10% change in the size of the lattice, which further proves its superiority over existing designs. This concept could find application in wearable devices that require high sensitivity to small mechanical fluctuations

Diversite De Rhizobia Dans Un Champ Cultive De Pois D’angole (Cajanus Cajan L.,) (Legumineuses) A Yamoussoukro (Centre Côte D’ivoire)

Le pois d'Angole (Cajanus cajan) est une importante légumineuse à graines cultivée dans les zones tropicales, notamment en Afrique de l'Ouest. Toutefois, dans cette partie de l'Afrique, la diversité des rhizobia nodulant la plante est peu connue, alors que son exploration peut permettre d'améliorer son intérêt particulièrement en agriculture. Cette étude vise à évaluer la diversité génétique des rhizobia nodulant un champ de pois d'Angole à Yamoussoukro (centre de la Côte d'Ivoire). Au total, 169 souches de rhizobia ont été isolées à partir de nodules collectés en champ. Le milieu synthétique TY utilisé pour cultiver et purifier les isolats, avant l'étude génétique, a permis de distinguer ceux-ci en deux groupes en fonction de la vitesse de croissance. La diversité génétique a été étudiée par PCR-RFLP du gène codant l'ARNr 16S des bactéries. L'analyse des produits de la digestion du gène ARNr 16S des isolats avec l'endonucléase Tsp 509I a révélé 3 différents génotypes, dans des proportions de 11,2 et 53,9 %, pour le moins représenté et le plus important, respectivement. Ces résultats montrent l'existence d'une variabilité physiologique et génétique au sein des rhizobia nodulant le pois d'Angole.Mots clés: Cajanus cajan, diversité, rhizobia, PCR-RFLP ADNr 16S, Côte d'IvoirePigeon pea (Cajanus cajan) is an important grain legume in tropical zone, notably in West Africa. However, in this area of Africa the diversity of rhizobia nodulating this plant is poorly understood even though its exploration can contribute to increase its interest, notably in agriculture. This work aims at determining the genetic diversity of rhizobia nodulating a pigeon pea field in Yamoussoukro (Center Ivory Coast). One hundred sixty-nine (169) rhizobia's strains were isolated from field nodules. The use of TY medium allowed the purification and identification of two groups according to their growth rate. PCR-RFLP analyses of the 16S rRNA genes with the endonuclease Tsp 509I enabled the characterization of three main genotypes within the pigeon pea nodulating rhizobia community. The occurrence of these genotypes varied from 11.2 % for the least to 53.9 % for the most important. These studies showed the evidence of physiological and genetic variability within the pigeon pea nodulating rhizobia strains

Ultra-stretchable active metasurfaces for high-performance structural color

Metamaterials as artificially structural materials exhibit customized properties unattainable in nature. While dynamic response is highly desired, metamaterials are usually passive and cannot be tuned post-fabrication. A conventional active metamaterial consists of rigid resonators mounted on flexible substrates that permit a limited amount of mechanical tuning. Given that rigid resonators permanently deform or debond under large strains (above 30%), the range of flexibility that is possible with tunable metamaterials is limited. Here, we propose a kirigami-inspired geometry that overcomes this limitation. The proposed design enhances stretchability exceeding 100% when compared with the existing design. A high degree of flexibility is achieved through “stress engineering” at the interface between rigid resonators and flexible substrates. Our design shows that the resonance modes shift at a rate of 3.32 ± 0.1 nm for every 1% change in strain, which is the highest tunability reported thus far. We demonstrate how this new concept can be applied to structural color. Using a single design, we demonstrated the full range of colors for the first time. The novel concept of highly stretchable metamaterials may revolutionize the field and enable its use in applications such as wearable sensors, smart displays, and switchable devices requiring extremely dynamic properties

In-Materio Extreme Learning Machines

Nanomaterial networks have been presented as a building block for unconventional in-Materio processors. Evolution in-Materio (EiM) has previously presented a way to congure and exploit physical materials for computation, but their ability to scale as datasets get larger and more complex remains unclear. Extreme Learning Machines (ELMs) seek to exploit a randomly initialised single layer feed forward neural network by training the output layer only. An analogy for a physical ELM is produced by exploiting nanomaterial networks as material neurons within the hidden layer. Circuit simulations are used to eciently investigate diode-resistor networks which act as our material neurons. These in-Materio ELMs (iM-ELMs) outperform common classication methods and traditional articial ELMs of a similar hidden layer size. For iM-ELMs using the same number of hidden layer neurons, leveraging larger more complex material neuron topologies (with more nodes/electrodes) leads to better performance, showing that these larger materials have a better capability to process data. Finally, iM-ELMs using virtual material neurons, where a single material is re-used as several virtual neurons, were found to achieve comparable results to iM-ELMs which exploited several dierent materials. However, while these Virtual iM-ELMs provide signicant exibility, they sacrice the highly parallelised nature of physically implemented iM-ELMs

Alignment of liquid crystal/carbon nanotube dispersions for application in unconventional computing

We demonstrate the manipulation of single-walled carbon nanotube/liquid crystal composites using in-plane electric fields. The conductivity of the materials is shown to be dependant on the application of a DC bias across the electrodes. When the materials are subjected to this in-plane field, it is suggested that the liquid crystals orientate, thereby forcing the SWCNTs to follow in alignment. This process occurs over many seconds, since the SWCNTs are significantly larger in size than the liquid crystals. The opportunity for applying this material to unconventional computing problems is suggested

Twist Symmetry and Classical Solutions in Open String Field Theory

We construct classical solutions of open string field theory which are not invariant under ordinary twist operation. From detailed analysis of the moduli space of the solutions, it turns out that our solutions become nontrivial at boundaries of the moduli space. The cohomology of the modified BRST operator and the CSFT potential evaluated by the level truncation method strongly support the fact that our nontrivial solutions correspond to the closed string vacuum. We show that the nontrivial solutions are equivalent to the twist even solution which was found by Takahashi and Tanimoto, and twist invariance of open string field theory remains after the shift of the classical backgrounds.Comment: 19 pages, 2 figures; v2: errors fixe