Profiling of oligolignols reveals monolignol coupling conditions in lignifying poplar xylem

Lignin is an aromatic heteropolymer, abundantly present in the walls of secondary thickened cells. Although much research has been devoted to the structure and composition of the polymer to obtain insight into lignin polymerization, the low-molecular weight oligolignol fraction has escaped a detailed characterization. This fraction, in contrast to the rather inaccessible polymer, is a simple and accessible model that reveals details about the coupling of monolignols, an issue that has raised considerable controversy over the past years. We have profiled the methanol-soluble oligolignol fraction of poplar (Populus spp.) xylem, a tissue with extensive lignification. Using liquid chromatography-mass spectrometry, chemical synthesis, and nuclear magnetic resonance, we have elucidated the structures of 38 compounds, most of which were dimers, trimers, and tetramers derived from coniferyl alcohol, sinapyl alcohol, their aldehyde analogs, or vanillin. All structures support the recently challenged random chemical coupling hypothesis for lignin polymerization. Importantly, the structures of two oligomers, each containing a γ-p-hydroxybenzoylated syringyl unit, strongly suggest that sinapyl p-hydroxybenzoate is an authentic precursor for lignin polymerization in poplar

Bacterial contamination of table eggs and the influence of housing systems

With the introduction of alternative housing systems for laying hens in the EU, recent research has focussed on the bacterial contamination of table eggs, e.g. eggshell and egg content contamination. Contamination of eggshells with aerobic bacteria is generally higher for nest eggs from non-cage systems compared to nest eggs from furnished cages or eggs from conventional cages. Studies indicate limited or no systematic differences in eggshell contamination with aerobic bacteria between eggs laid in the nest boxes of furnished cages and eggs laid in conventional cages. The major differences found in experimental studies between cage- and non-cage systems are less pronounced under commercial conditions. The effect of housing system on eggshell contamination with specific groups of bacteria is variable. Limited information is available on the influence of housing system on egg content contamination. Recent research does not indicate large differences in egg content contamination between eggs from cage- and non-cage systems (ignoring outside nest and floor eggs). The microflora of the eggshell is dominated by Gram-positive bacteria, whereas Gram-negative bacteria are best equipped to overcome the antimicrobial defences of the egg content. Much of the research on eggshell and egg content contamination focuses on Salmonella, since infection with Salmonella enteritidis, resulting from the consumption of contaminated eggs or egg products, is still a major health problem. Observed Salmonella prevalence on the eggshell and in the egg content vary, depending on the fact whether investigations were based on randomly sampled table eggs or on eggs from naturally infected hens. The limited information available on other pathogens shows that they are exclusively isolated from the eggshell and not from the internal contents

7,4'-Dihydroxyflavanone is the major Azorhizobium nod gene-inducing factor present in Sesbania rostrata seedling exudate

Exudate from Sesbania rostrata seedlings contains signaling compounds that induce the common nodABC operon of the bacterial symbiont Azorhizobium caulinodans ORS571. An Azorhizobium strain harboring a nodA::lacZ reporter fusion was used to monitor the nod-inducing activity of crude exudate fractions that were separated by reversed-phase chromatography. The major inducer was shown, by spectroscopic analysis and by comparison with chemically synthesized compounds, to be 7,4'-dihydroxyflavanone (liquiritigenin). Newly synthesized analogues, 7,3'-dihydroxyflavanone and 7,2'-dihydroxyflavanone, have only poor inducing activity

The development of a novel SNP genotyping assay to differentiate cacao clones

In this study, a double-mismatch allele-specific (DMAS) qPCR SNP genotyping method has been designed, tested and validated specifically for cacao, using 65 well annotated international cacao reference accessions retrieved from the Center for Forestry Research and Technology Transfer (CEFORTT) and the International Cocoa Quarantine Centre (ICQC). In total, 42 DMAS-qPCR SNP genotyping assays have been validated, with a 98.05% overall efficiency in calling the correct genotype. In addition, the test allowed for the identification of 15.38% off-types and two duplicates, highlighting the problem of mislabeling in cacao collections and the need for conclusive genotyping assays. The developed method showed on average a high genetic diversity (He = 0.416) and information index (I = 0.601), making it applicable to assess intra-population variation. Furthermore, only the 13 most informative markers were needed to achieve maximum differentiation. This simple, effective method provides robust and accurate genotypic data which allows for more efficient resource management (e.g. tackling mislabeling, conserving valuable genetic material, parentage analysis, genetic diversity studies), thus contributing to an increased knowledge on the genetic background of cacao worldwide. Notably, the described method can easily be integrated in other laboratories for a wide range of objectives and organisms

Thiol redox and pKa properties of mycothiol, the predomiant low molecular weight thiol cofactor in the Actinomycetes

Herein, the thiol pKa and standard redox potential of mycothiol, the major low molecular weight thiol cofactor in the actinomycetes, are reported. The measured standard redox potential reveals substantial discrepancies in one or more of the other previously measured intracellular parameters that are relevant to mycothiol redox biochemistry

Poultry as a host for the zoonotic pathogen Campylobacter jejuni

Campylobacteriosis is the most reported foodborne gastroenteritic disease and poses a serious health burden in industrialized countries. Disease in humans is mainly caused by the zoonotic pathogen Campylobacter jejuni. Due to its wide-spread occurrence in the environment, the epidemiology of Campylobacter remains poorly understood. It is generally accepted, however, that chickens are a natural host for Campylobacter jejuni, and for Campylobacter spp. in general, and that colonized broiler chicks are the primary vector for transmitting this pathogen to humans. Several potential sources and vectors for transmitting C. jejuni to broiler flocks have been identified. Initially, one or a few broilers can become colonized at an age of >2 weeks until the end of rearing, after which the infection will rapidly spread throughout the entire flock. Such a flock is generally colonized until slaughter and infected birds carry a very high C. jejuni load in their gastrointestinal tract, especially the ceca. This eventually results in contaminated carcasses during processing, which can transmit this pathogen to humans. Recent genetic typing studies showed that chicken isolates can frequently be linked to human clinical cases of Campylobacter enteritis. However, despite the increasing evidence that the chicken reservoir is the number one risk factor for disease in humans, no effective strategy exists to reduce Campylobachter prevalence in poultry flocks, which can in part be explained by the incomplete understanding of the epidemiology of C. jejuni in broiler flocks. As a result, the number of human campylobacteriosis cases associated with the chicken vector remains strikingly high

Physico-chemical properties of fourteen popular cocoa bean varieties in Dongnai-highland Vietnam

Cocoa (Theobroma cacao L.) is a major, crucial economic, global crop and has been maintained several nutritional benefits. The exporting volume of Vietnamese cocoa bean is increasing in the world cocoa trade. The beans of fourteen popular cocoa varieties that are commonly cultivated in Trang Bom (Dong Nai, Vietnam) were characterized for their physico-chemical qualifications on the background of post-fermented cocoa beans and dehydration in the region of Trang Bom-Dong Nai. The physical properties were determined based on mass ratio and bean’s dimension (lengh, width and thickness) as well as chemical (proximate) composition (total crude protein, ash, moisture, and lipid). These values were analysed using AOAC methods. The largest-size beans were found for the TD8 variety (1.5 g of mass, 25.02 mm of length, 14.28 mm of width and 7.96 mm of thickness). The moisture content of the cocoa beans was in the range between 5.64 and 6.99 (% wb) and the ash content in the range between 3.67% and 2.47% (wb). Noticeably, the fat content ratio (the most important value of cocoa bean) found in 8 varieties (TD1, TD2, TD5, TD9, TD11, TD12, TD13, TD14) was over 50%, thus these varieties are worthy chemical component especially for exported cocoa bean and industrized cultivation (extending the cultivation producing area)

Mass spectrometry-based fragmentation as an identification tool in lignomics

The ensemble of all phenolics for which the biosynthesis is coregulated with lignin biosynthesis, i.e., metabolites from the general phenylpropanoid, monolignol, and (neo)-lignan biosynthetic pathways and their derivatives, as well as the lignin oligomers, is coined the lignome. In lignifying tissues, the lignome comprises a significant portion of the metabolome. However, as is true for metabolomics in general, the structural elucidation of unknowns represents the biggest challenge in characterizing the lignome. To minimize the necessity to purify unknowns for NMR analysis, it would be desirable to be able to extract structural information from liquid chromatography-mass spectrometry data directly. However, mass spectral libraries for metabolomics are scarce, and no libraries exist for the lignome. Therefore, elucidating the gas-phase fragmentation behavior of the major bonding types encountered in lignome-associated molecules would considerably advance the systematic characterization of the lignome. By comparative MS" analysis of a series of molecules belonging to the beta-aryl ether, benzodioxane, phenylcoumaran, and resinol groups, we succeeded in annotating typical fragmentations for each of these bonding structures as well as fragmentations that enabled the identification of the aromatic units involved in each bonding structure. Consequently, this work lays the foundation for a detailed characterization of the lignome in different plant species, mutants, and transgenics and for the MS-based sequencing of lignin oligomers and (neo)lignans