Insights into the Structure and Protein Composition of Moorella thermoacetica Spores Formed at Different Temperatures

The bacterium Moorella thermoacetica produces the most heat-resistant spores of any spoilage-causing microorganism known in the food industry. Previous work by our group revealed that the resistance of these spores to wet heat and biocides was lower when spores were produced at a lower temperature than the optimal temperature. Here, we used electron microcopy to characterize the ultrastructure of the coat of the spores formed at different sporulation temperatures; we found that spores produced at 55 °C mainly exhibited a lamellar inner coat tightly associated with a diffuse outer coat, while spores produced at 45 °C showed an inner and an outer coat separated by a less electron-dense zone. Moreover, misarranged coat structures were more frequently observed when spores were produced at the lower temperature. We then analyzed the proteome of the spores obtained at either 45 °C or 55 °C with respect to proteins putatively involved in the spore coat, exosporium, or in spore resistance. Some putative spore coat proteins, such as CotSA, were only identified in spores produced at 55 °C; other putative exosporium and coat proteins were significantly less abundant in spores produced at 45 °C. Altogether, our results suggest that sporulation temperature affects the structure and protein composition of M. thermoacetica spores.

Nanotechnologies in agricultural production as a factor of transition to a new level of technological design

The article discusses one of the directions of the transition of agricultural production in Russia to the sixth technological order based on the introduction of nanotechnology in the field of hygrothermal effects on grain crops. The features of hygrothermal action on grain under vacuum conditions are presented. The distinctive features of such processing as nanotechnology are substantiated. Based on the method of similarity in the functioning of technical systems for vacuum-capillary processes of humidification, drying, and wet-heat treatment, generalized similarity criteria are obtained, their numerical values are determined, and generalized criterion dependences of the intensity of the processes under consideration on the processing parameters are obtained. The implementation of this method made it possible to quantitatively describe the processes of vacuum capillary hygrothermal treatment of grain, to assign processing parameters and control them.

Research on Aging Resistance of Three Phase Composites for Anti-collision Intelligent Control of Bridge Engineering

Aminated Carbon Nanotubes (CNTs) and Carbon Fiber (CF) materials for anticollision intelligent control of Bridge Engineering were used to enhance the properties of Bismaleimide Resin (BMI) matrix resin and then tested the moist heat aging, salt spray aging and erosion resistance in this study. The resulted show that when the aging time was 168h, after wet heat and salt spray, the flexural strength and impact strength of three-phase composites with 1.5wt% MWNTs-NH2 content can reach maximum, and the wet heat aging bending performance is 45% better than that of non-added carbon nanotubes, the impact performance is 41% higher, the salt spray aging bending performance is 43% higher and the salt spray aging impact performance is 32% higher.

Genetic determinants of stress resistance in desiccated Salmonella enterica

Enteric pathogens including Salmonella are capable of long-term survival after desiccation, and resist heat treatment that are lethal to hydrated cells. The mechanisms of dry-heat resistance differ from wet heat resistance. To elucidate the mechanisms of dry-heat resistance in Salmonella , screening of the dry-heat resistance of 108 Salmonella strains representing 39 serotypes identified the 22 most resistant and the 8 most sensitive strains for comparative genome analysis. A total of 289 genes of the accessory genome were differently distributed between resistant and sensitive strains. Among these genes, 28 proteins with a putative relationship to stress resistance were selected for to quantify relative gene expression before and after desiccation, and expression by solid-state cultures on agar plates relative to cultures growing in liquid culture media. Of these 28 genes, 15 genes were upregulated ( P <0.05) after desiccation, or by solid-state cultures on agar plates. These 15 genes were cloned into the low-copy vector pRK767 under control of the lacZ promoter. The expression of 6 of these 15 genes of these genes increased ( P <0.05) resistance to dry-heat and to treatment with 500 MPa. Our finding extends the knowledge of mechanisms of stress resistance in desiccated Salmonella to improve their control in dry food. IMPORTANCE This study directly targeted an increasing threat to food safety and developed knowledge and targeted strategies that can be used by the food industry to help reduce the risk of foodborne illness in their dry products and thereby reduce the overall burden of foodborne illness. Genomic and physiological analyses have elucidated mechanisms of bacterial resistance to many food preservation technologies including heat, pressure, disinfection chemicals, and UV light; however, information on bacterial mechanisms of resistance to dry-heat is scarce. Mechanisms of tolerance to desiccation likely also contribute to resistance to dry-heat but this assumption has not been verified experimentally. It remains unclear how mechanisms of resistance to wet heat relate to dry-heat resistance. This study will thus fill a knowledge gap to improve the safety of dry foods.

Moisture Vapor Resistance of Coated and Laminated Breathable Fabrics Using Evaporative Wet Heat Transfer Method

This study examined the effects of the fiber materials, fabric structural parameters, and surface modification method on the moisture vapor resistance of coated and laminated fabrics according to the measuring method in comparison with evaporative wet heat transfer method. The moisture vapor resistance (Ref) of the coated and laminated fabrics measured using evaporative wet heat transfer method was much more precise than water vapor transmission rate (WVTR) and water vapor permeability (WVP) measured using American Society for Testing and Materials (ASTM) and Japanese Industrial Standard (JIS) methods. The correlation coefficient between Ref and WVTR in the laminated and coated polyethylene terephthalate (PET) fabric specimens was the highest, i.e., −0.833, and −0.715, in coated fabric specimens. Hence, selecting an appropriate measuring method according to the fabric materials and surface modification method is very critical. According to curvilinear regression analysis, the influential factor affecting breathability of the PET fabric specimens measured using evaporative wet heat transfer method was fabric weight (R2 = 0.847) and fabric thickness (R2 = 0.872) in the laminated fabric specimens. Meanwhile, as per multiple linear regression, the most influential fabric structural parameters affecting the breathability of laminated fabric specimens measured using evaporative wet heat transfer method were the fabric density, weight/thickness, and weight followed by the fabric thickness (R2 = 0.943). These results would be valid for laminated breathable fabrics with characteristics within the range of this study and are of practical use for engineering laminated fabrics with high breathability.

Clostridioides difficile SpoVAD and SpoVAE interact and are required for DPA uptake into spores

Clostridioides difficile spores, like the spores from most endospore-forming organisms, are a metabolically dormant stage of development with a complex structure that conveys considerable resistance to environmental conditions, e.g. , wet heat. This resistance is due to the large amount of dipicolinic acid (DPA) that is taken up by the spore core, preventing rotational motion of the core proteins. DPA is synthesized by the mother cell and its packaging into the spore core is mediated by the products of the spoVA operon, which has a variable number of genes, depending on the organism. C. difficile encodes 3 spoVA orthologues, spoVAC, spoVAD, and spoVAE. Prior work has shown that C. difficile SpoVAC is a mechanosensing protein responsible for DPA release from the spore core upon the initiation of germination. However, the roles of SpoVAD and SpoVAE remain unclear in C. difficile . In this study we analyzed the roles of SpoVAD and SpoVAE and found that they are essential for DPA uptake into the spore, similar to SpoVAC. Using split luciferase protein interaction assays we found that these proteins interact, and we propose a model where SpoVAC/SpoVAD/SpoVAE proteins interact at or near the inner spore membrane, and each member of the complex is essential for DPA uptake into the spore core. Importance C. difficile spore heat resistance provides an avenue for it to survive the disinfection protocols in hospital and community settings. The spore heat resistance is mainly the consequence of the high DPA content within the spore core. By elucidating the mechanism by which DPA is taken up by the spore core, this study may provide insight in how to disrupt the spore heat resistance with the aim of making the current disinfection protocols more efficient at preventing the spread of C. difficile in the environment.

Mask decontamination methods (model N95) for respiratory protection: a rapid review

Background N95 respiratory protection masks are used by healthcare professionals to prevent contamination from infectious microorganisms transmitted by droplets or aerosols. Methods We conducted a rapid review of the literature analyzing the effectiveness of decontamination methods for mask reuse. The database searches were carried out up to September 2020. The systematic review was conducted in a way which simplified the stages of a complete systematic review, due to the worldwide necessity for reliable fast evidences on this matter. Results A total of 563 articles were retrieved of which 48 laboratory-based studies were selected. Fifteen decontamination methods were included in the studies. A total of 19 laboratory studies used hydrogen peroxide, 21 studies used ultraviolet germicidal irradiation, 4 studies used ethylene oxide, 11 studies used dry heat, 9 studies used moist heat, 5 studies used ethanol, two studies used isopropanol solution, 11 studies used microwave oven, 10 studies used sodium hypochlorite, 7 studies used autoclave, 3 studies used an electric rice cooker, 1 study used cleaning wipes, 1 study used bar soap, 1 study used water, 1 study used multi-purpose high-level disinfection cabinet, and another 1 study used chlorine dioxide. Five methods that are promising are as follows: hydrogen peroxide vapor, ultraviolet irradiation, dry heat, wet heat/pasteurization, and microwave ovens. Conclusions We have presented the best available evidence on mask decontamination; nevertheless, its applicability is limited due to few studies on the topic and the lack of studies on real environments.