Uptake of insecticides and fungicides by impregnable and refractory coniferous wood species treated with commercial bio-based emulsion gel formulations

Even in dry state, wood can be prone to biological degradation. Preservation is a prerequisite to confer protection and durability to wood. This is conventionally achieved by impregnating the wood with pesticides. A key point in these treatments is the complex process of wood penetrability. We focused on the relation between the penetration of wood preservatives, wood microstructure, and the physical characteristics of formulations in the impregnation of the easily impregnable pine (Pinus sylvestris), and the refractory spruce (Picea abies). In this work, specimens from the two species were impregnated with three types of commercial bio-based emulsion gels formulations containing insecticides and fungicides. The effect of treatment method using dipping, surface spraying, and vacuum-impregnation, on the retention of the active agents was analyzed. Visual assessment, and qualitative and quantitative analyses of cypermethrin, permethrin and  propiconazole by gas liquid chromatography coupled to mass spectroscopy showed enhanced penetration of the active agents, and revealed differences of penetration performance of each agent. The suitable combinations of solvents and surfactants used in the bio-based formulations enabled rapid wood penetration and high yields retention. The capacity of penetration and retention of our gel formulations is discussed in terms of the connectivity of the conducting cells network of the two wood species

Molecular phenotyping of the pal1 and pal2 mutants of Arabidopsis thaliana reveals far-reaching consequences on phenylpropanoid, amino acid, and carbohydrate metabolism

The first enzyme of the phenylpropanoid pathway, Phe ammonia-lyase (PAL), is encoded by four genes in Arabidopsis thaliana. Whereas PAL function is well established in various plants, an insight into the functional significance of individual gene family members is lacking. We show that in the absence of clear phenotypic alterations in the Arabidopsis pall and pal2 single mutants and with limited phenotypic alterations in the pall pal2 double mutant, significant modifications occur in the transcriptome and metabolome of the pal mutants. The disruption of PAL led to transcriptomic adaptation of components of the phenylpropanoid biosynthesis, carbohydrate metabolism, and amino acid metabolism, revealing complex interactions at the level of gene expression between these pathways. Corresponding biochemical changes included a decrease in the three major flavonol glycosides, glycosylated vanillic acid, scopolin, and two novel feruloyl malates coupled to coniferyl alcohol. Moreover, Phe overaccumulated in the double mutant, and the levels of many other amino acids were significantly imbalanced. The lignin content was significantly reduced, and the syringyl/guaiacyl ratio of lignin monomers had increased. Together, from the molecular phenotype, common and specific functions of PAL1 and PAL2 are delineated, and PAL1 is qualified as being more important for the generation of phenylpropanoids

The wood cell wall at the ultrastructural scale formation and topochemical organization

The macromolecular organization of the secondary wall of the cells from tree xylem is in large part responsible for the mechanical and physiological properties of wood. Modeling secondary walls of wood is difficult because information about their macromolecular architecture at the ultrastructural scale is missing. Numerous microscopic studies have provided views of the lignocellulosic composite material, but nanoscale distribution of the polymers and their interaction in muro is still not clearly understood. The intimate macromolecular organization of cell walls is defined during their differentiation. It is at the stage of wall thickening corresponding to secondary wall development that the topochemical organization and the interactions between cellulose, hemicelluloses and lignin are established.Using the conjunction of the high resolution of transmission electron microscopy (TEM) and the specificity of immunological probes directed against the main cell wall polymers, we investigated the deposition of hemicelluloses and lignins from the early stage of cambium differentiation to the mature fiber and vessel walls in growing model plants of Arabidopsis thaliana and poplar. TEM examination of differentiating cells as well as various wood and wood –derived materials and genetic plant mutants brought multiple evidence of the lamellar sub-organization of the secondary walls. Immuno-gold labeling showed that two structurally different xylan types were deposited at different stages in the wall thickening. Similarly two different types of lignin molecules were shown to be differentially polymerized at different steps of the building of the wall, lignin molecules of the condensed type being first deposited at the earliest stage of secondary thickening before the non-condensed  types. This process may be modified in response to environmental factors, as in tension wood.The spatio-temporal relationships occurring between hemicelluloses, lignin and cellulose microfibrils (CMFs) during the secondary wall development suggest that xylans with less substituted chains would be more directly interacting with CMFs than those with higher substitution patterns. It also suggests that lignin molecules of the non-condensed type have a function in bringing cohesion between the lamellae of CMFs. A model of wall assembly during secondary thickening is proposed

Visualization of the action of ligninolytic enzymes on high yield pulp fibers

High-yield pulps from wheat straw and from poplar wood were treated with manganese-peroxidase (MnP) or with laccase (Lac), before and after a second refining stage

Structure of the iron-binding exopolysaccharide produced anaerobically by the Gram-negative bacterium Klebsiella oxytoca BAS-10.

Klebsiella oxytoca BAS-10 is a Gram-negative micro-organism capable of growing on high concentrations of heavy metals. This bacterium produces large amounts of an iron-binding exopolysaccharide that, in the presence of metallic cations, precipitates as a dense gel. The primary and secondary structure of the repeating unit of such polysaccharide has been characterised by chemical and spectroscopic methods, resulting in the following heptasaccharide: 2)-α-Rha-(1_3)- β-Gal-(1_2)-α-Rha-(1_4)-β-GlcA-[β-GlcA-(1_4)]-(1_3)-α- Rha-(1_3)-α-Rha-(1_. The absolute configurations for the Rha units are L, while those for the GlcA and Gal residues are D

The Escherichia coli cell cycle

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28767/1/0000599.pd

Insights into the Molecular Basis of L-Form Formation and Survival in Escherichia coli

L-forms have been shown to occur among many species of bacteria and are suspected to be involved in persistent infections. Since their discovery in 1935, numerous studies characterizing L-form morphology, growth, and pathogenic potential have been conducted. However, the molecular mechanisms underlying the formation and survival of L-forms remain unknown. Using unstable L-form colonies of Escherichia coli as a model, we performed genome-wide transcriptome analysis and screened a deletion mutant library to study the molecular mechanisms involved in formation and survival of L-forms. Microarray analysis of L-form versus classical colonies revealed many up-regulated genes of unknown function as well as multiple over-expressed stress pathways shared in common with persister cells and biofilms. Mutant screens identified three groups of mutants which displayed varying degrees of defects in L-form colony formation. Group 1 mutants, which showed the strongest defect in L-form colony formation, belonged to pathways involved in cell envelope stress, DNA repair, iron homeostasis, outer membrane biogenesis, and drug efflux/ABC transporters. Four (Group 1) mutants, rcsB, a positive response regulator of colanic acid capsule synthesis, ruvA, a recombinational junction binding protein, fur, a ferric uptake regulator and smpA a small membrane lipoprotein were selected for complementation. Complementation of the mutants using a high-copy overexpression vector failed, while utilization of a low-copy inducible vector successfully restored L-form formation. This work represents the first systematic genetic evaluation of genes and pathways involved in the formation and survival of unstable L-form bacteria. Our findings provide new insights into the molecular mechanisms underlying L-form formation and survival and have implications for understanding the emergence of antibiotic resistance, bacterial persistence and latent infections and designing novel drugs and vaccines