Visualization of microbe-dietary remnant interactions in digesta from pigs, by fluorescence in situ hybridization and staining methods; effects of a dietary arabinoxylan-rich wheat fraction

This study investigated how the addition of a specific hydrocolloid, arabinoxylan (AX), to the pig diets containing red meat, affected the gut microbiota in terms of changes to the bacterial community dynamics. Fluorescence in situ hybridization (FISH) was used to enumerate both broad groups and particular bacterial species, and showed systematic differences in pigs fed AX. In addition, the role of bacteria in the fermentation of dietary substrates was studied by visualizing direct associations between the bacteria and substrate particles. To achieve this, novel methods of combining histological staining or enzymatic labelling with FISH protocols were established. In this way, undigested and/or unfermented remnants of meat, endogenous mucin, and several plant cell wall hydrocolloids (cellulose, lignin and arabinoxylan) were distinguished, together with large intestine microbiota under brightfield and/or confocal laser scanning microscopy (CLSM). It was evident that no apparent direct associations occurred between specific classes or groups of bacteria and meat, mucin, lignin or AX remnants. In contrast, bacteria belonging to Clostridium clusters XIVa and XIVb formed a strong (P < 0.01) direct association with cellulose remnants in the pig digesta in the caecum

Effects of tea extracts on the colonization behaviour of Candida species:attachment inhibition and biofilm enhancement

Purpose. We assessed the effects of four different types of tea extracts (green, oolong, black and pu-erh tea) on cellular surface properties (hydrophobicity and auto-aggregation) and the colonization attributes (attachment and biofilm formation) of four strains of Candida albicans and three strains of Candida krusei. Methodology. The cellular surface properties were determined using spectrophotometry. The colonization activities were quantified using colorimetric viability assays and visualized using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Results. The tea extracts, in general, reduced the hydrophobicity (by 8-66%) and auto-aggregation (by 20-65%), and inhibited the attachment of two C. krusei strains (by 41-88%). Tea extracts enhanced the biofilm formation of one C. albicans and two C. krusei strains (by 1.4-7.5-fold). The observed reduction in hydrophobicity strongly correlated with the reduction in attachment of the two C. krusei strains (

Mechanical properties of bacterial cellulose synthesised by diverse strains of the genus Komagataeibacter

Bacterial cellulose (BC) has several current and potential future uses in the food industry because of its ability to form hydrogels with distinctive properties. The texture of BC hydrogels is determined by both the cellulose fibre network and the internal dispersed water. In this study, mechanical properties of hydrated BC synthesised by six different strains of Komagataeibacter genus were investigated with regards to their extensibility, compressive strength, relaxation ability, viscoelasticity and poroelasticity. The stress/strain at failure and Young's modulus were assessed by uniaxial tensile testing. The compressive strength, relaxation ability and viscoelasticity were measured via a series of compression and small amplitude oscillatory shear steps. A poroelastic constitutive modelling simulation was used to investigate the mechanical effects of water movement. The morphology of the BC fibril network under compression was observed via scanning electron microscopy. Results showed that the mechanics of BC were highly dependent on the cellulose concentration, as well as the morphology of the fibril network. BC synthesised by ATCC 53524 was the most concentrated (0.71 wt%), and exhibited high tensile properties, stiffness and storage moduli; whereas comparatively low mechanical properties were noted for BC produced by ATCC 700178 and ATCC 10245, which contained the lowest cellulose concentration (0.18 wt%). Small deformation responses (normal stress, G′) scaled with cellulose concentration for all samples, whereas larger deformation responses (Young's modulus, poroelasticity) depended on both cellulose concentration and additional factors, presumably related to network morphology. Increasing concentration and compressive coalescence of fibres in the integrated BC network reduced both the relaxation of the normal stress and the movement of water. This research aids the selection of bacterial strains to modulate the texture and mechanical properties of hydrated BC-based food systems

Aluminium effects on mechanical properties of cell wall analogues

Aluminium (Al) toxicity adversely impacts plant productivity in acid soils by restricting root growth and although several mechanisms are involved the physiological basis of decreased root elongation remains unclear. Understanding the primary mechanisms of Al rhizotoxicity is hindered due to the rapid effects of soluble Al on root growth and the close proximity of many cellular components within the cell wall, plasma membrane, cytosol and nucleus with which Al may react. To overcome some of these difficulties, we report on a novel method for investigating Al interactions with Komagataeibacter xylinus bacterial cellulose (BC)-pectin composites as cell wall analogues. The growth of K. xylinus in the presence of various plant cell wall polysaccharides, such as pectin, has provided a unique in vitro model system with which to investigate the interactions of Al with plant cell wall polysaccharides. The BC-pectin composites reacted in a similar way with Al as do plant cell walls, providing insights into the effects of Al on the mechanical properties of the BC-pectin composites as cell wall analogues. Our findings indicated that there were no significant effects of Al (4-160 μM) on the tensile stress, tensile strain or Young's modulus of the composites. This finding was consistent with cellulose, not pectin, being the major load bearing component in BC-pectin composites, as is also the case in plant cell walls

Extracellular depolymerisation triggers fermentation of tamarind xyloglucan and wheat arabinoxylan by a porcine faecal inoculum

Arabinoxylan (AX) and xyloglucan (XG) are important components of primary cell walls of cereal grains and vegetables/fruits, respectively. Despite the established health benefits of these non-starch polysaccharides, the mechanisms of their utilisation by the gut microbiota are poorly understood. In this study, the mechanisms of solubilised wheat AX and tamarind XG degradation were investigated under in vitro fermentation conditions using a porcine faecal inoculum. Through structural analysis of the polymers, we demonstrate that depolymerisation by microbial surface accessible endo-degrading enzymes occurs prior to active fermentation of AX or XG. Breakdown products are released into the medium and potentially utilised cooperatively by other microbes. Acetate and propionate are the main fermentation products and are produced concurrently with polysaccharide depletion. Butyrate, however, is produced more slowly consistent with it being a secondary metabolite

High Molecular Weight Mixed-Linkage Glucan as a Mechanical and Hydration Modulator of Bacterial Cellulose:Characterization by Advanced NMR Spectroscopy

Bacterial cellulose (BC) consists of a complex three-dimensional organization of ultrafine fibers which provide unique material properties such as softness, biocompatibility, and water-retention ability, of key importance for biomedical applications. However, there is a poor understanding of the molecular features modulating the macroscopic properties of BC gels. We have examined chemically pure BC hydrogels and composites with arabinoxylan (BC-AX), xyloglucan (BC-XG), and high molecular weight mixed-linkage glucan (BC-MLG). Atomic force microscopy showed that MLG greatly reduced the mechanical stiffness of BC gels, while XG and AX did not exert a significant effect. A combination of advanced solid-state NMR methods allowed us to characterize the structure of BC ribbons at ultra-high resolution and to monitor local mobility and water interactions. This has enabled us to unravel the effect of AX, XG, and MLG on the short-range order, mobility, and hydration of BC fibers. Results show that BC-XG hydrogels present BC fibrils of increased surface area, which allows BC-XG gels to hold higher amounts of bound water. We report for the first time that the presence of high molecular weight MLG reduces the density of clusters of BC fibrils and dramatically increases water interactions with BC. Our data supports two key molecular features determining the reduced stiffness of BC-MLG hydrogels, that is, (i) the adsorption of MLG on the surface of BC fibrils precluding the formation of a dense network and (ii) the preorganization of bound water by MLG. Hence, we have produced and fully characterized BC-MLG hydrogels with novel properties which could be potentially employed as renewable materials for applications requiring high water retention capacity (e.g. personal hygiene products)

Investigation of the micro- and nano-scale architecture of cellulose hydrogels with plant cell wall polysaccharides: a combined USANS/SANS study

The structure of protiated, deuterated and composite cellulose hydrogels with plant cell wall (PCW) polysaccharides has been investigated by combined USANS/SANS experiments, complemented with spectroscopy and microscopy. The broad size range covered by the USANS/SANS experiments enabled the identification of cellulose architectural features in the cross-sectional and longitudinal directions. In the cross-sectional direction, cellulose ribbons are modelled as core-shell structures. Xyloglucan and mixed linkage glucans interfere with the cellulose crystallisation process, reducing the crystallinity and establishing cross-bridges between ribbons. However, only xyloglucan is able to establish strong interactions with the cellulose microfibrils, affecting the properties of the ribbons' core. Longitudinally, the ribbons are hypothesised to present a ca. 1.4-1.5 μm periodic twist with a crystallite length of ca. 140-180 nm for the individual microfibrils. These results highlight the potential of USANS/SANS techniques to investigate the multi-scale architecture of cellulose hydrogels as well as the interaction mechanism between cellulose and PCW polysaccharides

Improving medical certification of cause of death: effective strategies and approaches based on experiences from the Data for Health Initiative.

BACKGROUND: Accurate and timely cause of death (COD) data are essential for informed public health policymaking. Medical certification of COD generally provides the majority of COD data in a population and is an essential component of civil registration and vital statistics (CRVS) systems. Accurate completion of the medical certificate of cause of death (MCCOD) should be a relatively straightforward procedure for physicians, but mistakes are common. Here, we present three training strategies implemented in five countries supported by the Bloomberg Philanthropies Data for Health (D4H) Initiative at the University of Melbourne (UoM) and evaluate the impact on the quality of certification. METHODS: The three training strategies evaluated were (1) training of trainers (TOT) in the Philippines, Myanmar, and Sri Lanka; (2) direct training of physicians by the UoM D4H in Papua New Guinea (PNG); and (3) the implementation of an online and basic training strategy in Peru. The evaluation involved an assessment of MCCODs before and after training using an assessment tool developed by the University of Melbourne. RESULTS: The TOT strategy led to reductions in incorrectly completed certificates of between 28% in Sri Lanka and 40% in the Philippines. Following direct training of physicians in PNG, the reduction in incorrectly completed certificates was 30%. In Peru, the reduction in incorrect certificates was 30% after implementation and training on an online system only and 43% after training on both the online system and basic medical certification principles. CONCLUSIONS: The results of this study indicate that a variety of training strategies can produce benefits in the quality of certification, but further improvements are possible. The experiences of D4H suggest several aspects of the strategies that should be further developed to improve outcomes, particularly key stakeholder engagement from early in the intervention and local committees to oversee activities and support an improved culture in hospitals to support better diagnostic skills and practices