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Despite numerous studies on Salmonella enterica subsp. enterica serovar Typhimurium, the underlying mechanisms of several aspects of its virulence are still under investigation, including the role of the pdu and ttrA genes, associated with the metabolism of 1,2-propanediol using tetrathionate as an electron acceptor respectively. Our objective was to contribute to an understanding of the role of these genes inbacterial virulence for mice (Mus musculus) using an S. Typhumirum ΔttrApduA mutant. The experiment was conducted with a group infected by the S. Typhimurium mutant and a control group infected with a wild-type strain. The mutant was not attenuated compared with the parent strain. There were no differences in the bacterial numbers recovered from the mesenteric lymph nodes and Peyer's patches but at 8-day after oral infection higher numbers were recovered from the spleen, liver, and cecum. Unlike the single pduA and ttrA mutants, the double ΔttrApduA mutation did not affect invasion and survival in mice, which highlights the need for further studies to clarify the role of these important metabolism genes under reduced redox conditions linked to Salmonella virulence.

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In mammals, enteric salmonellas can use tetrathionate (ttr), formed as a by-product from the inflammatory process in the intestine, as electron acceptor in anaerobic respiration, and it can fuel its energy metabolism by degrading the microbial fermentation product 1,2-propanediol. However, recent studies have shown that this mechanism is not important for Salmonella infection in the intestine of poultry, while it prolongs the persistence of Salmonella at systemic sites in this species. In the current study, we show that ΔttrApduA strains of Salmonella enterica have lower net survival within chicken-derived HD-11 macrophages, as CFU was only 2.3% (S. Enteritidis ΔttrApduA), 2.3% (S. Heidelberg ΔttrApduA), and 3.0% (S. Typhimurium ΔttrApduA) compared to wild-type strains after 24 h inside HD-11 macrophage cells. The difference was not related to increased lysis of macrophages, and deletion of ttrA and pduA did not impair the ability of the strains to grow anaerobically. Further studies are indicated to determine the reason why Salmonella ΔttrApduA strains survive less well inside macrophage cell lines.

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It is well known that polar organic compounds, such as alcohols and polyols, exert an appreciable influence on water structure and thus have important effects on surfactant micellization. These substances are often used to modify the properties of surfactants in aqueous solutions, increasing the practical applications they have in diverse industries. In this work, the critical micelle concentration (CMC) of decyltrimethylammonium bromide (C10TAB) in water and in 1,2-propanediol aqueous solutions was determined from both sound velocity and surface tension measurements as a function of surfactant concentration in the temperature range of (293.15 to 308.15) K. The critical micelle concentration of the surfactant increases as the concentration of 1,2-propanediol becomes higher, while the effect on temperature does not show important changes within the range considered. At the selected temperatures, the standard thermodynamic parameters of micellization suggests that the addition of 1,2-propanediol makes the micellization process less favorable. Thermodynamic analysis suggests that the micelle formation of C10TAB is an entropy-driven process at the temperatures considered in this study.

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Among the important recent observations involving anaerobic respiration was that an electron acceptor produced as a result of an inflammatory response to Salmonella Typhimurium generates a growth advantage over the competing microbiota in the lumen. In this regard, anaerobically, salmonellae can oxidize thiosulphate (S2O32-) converting it into tetrathionate (S4O62-), the process by which it is encoded by ttr gene cluster (ttrSRttrBCA). Another important pathway under aerobic or anaerobic conditions is the 1,2-propanediol-utilization mediated by the pdu gene cluster that promotes Salmonella expansion during colitis. Therefore, we sought to compare in this study, whether Salmonella Heidelberg strains lacking the ttrA, ttrApduA, and ttrACBSR genes experience a disadvantage during cecal colonization in broiler chicks. In contrast to expectations, we found that the gene loss in S. Heidelberg potentially confers an increase in fitness in the chicken infection model. These data argue that S. Heidelberg may trigger an alternative pathway involving the use of an alternative electron acceptor, conferring a growth advantage for S. Heidelberg in chicks.

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Salmonella enterica serovars use self-induced intestinal inflammation to increase electron acceptor availability and to obtain a growth advantage in the host gut. There is evidence suggesting that the ability of Salmonella to use tetrathionate and 1,2-propanediol provides an advantage in murine infection. Thus, we present here the first study to evaluate both systemic infection and faecal excretion in commercial poultry challenged by Salmonella Enteritidis (SE) and S. Typhimurium (STM) harbouring deletions in ttrA and pduA genes, which are crucial to the metabolism of tetrathionate and 1,2-propanediol, respectively. Mutant strains were excreted at higher rates when compared to the wild-type strains. The highest rates were observed with white egg-layer and brown egg-layer chicks (67.5%), and broiler chicks (56.7%) challenged by SEΔttrAΔpduA, and brown egg-layer chicks (64.8%) challenged by STMΔttrAΔpduA. SEΔttrAΔpduA presented higher bacterial counts in the liver and spleen of the three chicken lineages and caecal contents from the broiler chickens, whereas STMΔttrAΔpduA presented higher counts in the liver and spleen of the broiler and brown-egg chickens for 28 days post-infection (P < 0.05). The ttrA and pduA genes do not appear to be major virulence determinants in faecal excretion or invasiveness for SE and STM in chickens. RESEARCH HIGHLIGHTSttrA and pudA do not impair gut colonization or systemic infection in chicks.Mutant strains were present in higher numbers in broilers than in laying chicks.Mutants of SE and STM showed greater pathogenicity in broiler chicks than layers.

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Background: New directions of research on lactic acid bacteria include investigation of metabolic pathways for the synthesis and/or metabolism of 1,2-propanediol, commonly used in the food and chemical industry, medicine, pharmacy and cosmetology as well as agriculture. The objective of this study was to compare the capacity of strains representing three diverse heterofermentative species belonging to the genus Lactobacillus to synthesize and/or transform 1,2-PD as well as to suggest new directions of research aimed at commercial use of this metabolite. Results: The novel strain of Lactobacillus buchneri A KKP 2047p, characterized as exhibiting an unusual trait for that species in the form of capacity to metabolize 1,2-PD, grew poorly in a medium containing 1,2-PD as a sole carbon source. The supplementation with glucose facilitated rapid growth of bacteria and use of 1,2-PD for the synthesis of propionic acid. A similar observation was noted for Lactobacillus reuteri. On the other hand, Lactobacillus diolivorans effectively metabolized 1,2-PD which was the sole carbon source in the medium, and the addition of glucose inhibited the synthesis of propionic acid. The experiments also investigated the effect of cobalamin as a diol dehydratase coenzyme involved in the propionic acid synthesis from 1,2-PD whose addition promoted the yield of the reaction in the case of all tested strains. Conclusions: All tested isolates showed the ability to effectively metabolize 1,2-PD (in the presence of cobalamin) and its conversion to propionic acid, which reveals that investigated bacteria meet the essential requirements of microorganisms with a potential application.

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Sugar cane (Saccharum spp.) is a forage crop widely used in animal feed because of its high dry matter (DM) production (25 to 40 t/ha) and high energy concentration. The ensiling of sugar cane often incurs problems with the growth of yeasts, which leads to high losses of DM throughout the fermentative process. The selection of specific inoculants for sugar cane silage can improve the quality of the silage. The present study aimed to select strains of lactic acid bacteria (LAB) isolated from sugar cane silage and to assess their effects when used as additives on the same type of silage. The LAB strains were inoculated into sugar cane broth to evaluate their production of metabolites. The selected strains produced higher concentrations of acetic and propionic acids and resulted in better silage characteristics, such as low yeast population, lower ethanol content, and lesser DM loss. These data confirmed that facultative heterofermentative strains are not good candidates for sugar cane silage inoculation and may even worsen the quality of the silage fermentation by increasing DM losses throughout the process. Lactobacillus hilgardii strains UFLA SIL51 and UFLA SIL52 resulted in silage with the best characteristics in relation to DM loss, low ethanol content, higher LAB population, and low butyric acid content. Strains UFLA SIL51 and SIL52 are recommended as starter cultures for sugar cane silage.

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The aim of this work was to study the microbial communities and volatile compounds profile of different fermentations: using four different cocoa hybrids and adding Saccharomyces cerevisiae UFLA CA11 as starter culture. Each hybrid showed particular characteristics: size, peel, seed and pulp. The temperature of the cocoa mass increased during fermentations (24°C to 47°C). The hybrid FA13 inoculated with S. cerevisiae showed the lowest temperatures (26 to 37°C). The pulp's compositions were different between the hybrids, mainly regarding citric acid (0.5 to 3.2g/kg). The carbohydrates were more rapidly (60h) metabolized in inoculated fermentations than in spontaneous fermentations (84h). Thirty-nine volatile compounds were identified by GC-FID for all fermentation processes. Esters (14 compounds) and alcohols (12) were the most important groups. Yeast communities were similar among the different processes while bacterial communities were dependent on the hybrid and process. The inoculation accelerated the fermentation and the hybrid characteristics influenced on the fermentation requiring particular management.

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Excess molar volumes and partial molar volumes were investigated from density values for a) ethanol (1) + water (2), b) 1,2-propanediol (1) + water (2), and c) ethanol (1) + 1,2-propanediol (2) mixtures, at temperatures from (278.15 to 288.15) K. Excess molar volumes were fitted by Redlich-Kister equation. The systems exhibit negative excess volumes probably due to increased interactions like hydrogen bonding and/or large differences in molar volumes of components. The Jouyban-Acree model was used for density and molar volume correlations of the studied mixtures at different temperatures. The mean relative deviations between experimental and calculated data in density data were 0.15, 0.08, and 0.01 %, for a), b), and c), respectively; whereas, in molar volume data the values were 1.9, 2.1, and 0.1 %, for a), b), and c), respectively.

En este trabajo se calcularon los volúmenes molares de exceso a partir de valores de densidad para los sistemas a) etanol + agua, b) 1,2-propanodiol + agua y c) etanol + 1,2-propanodiol, en todo el intervalo de composición, a temperaturas entre 278,15 y 288,15 K. Los volúmenes molares de exceso se modelaron de acuerdo a la ecuación de Redlich-Kister. Los sistemas estudiados presentan volúmenes de exceso altamente negativos probablemente debido a las fuertes interacciones por unión de hidrógeno entre las moléculas de los dos compuestos y a la gran diferencia en los volúmenes molares de los dos componentes puros. Finalmente se usó el modelo Jouyban-Acree para correlacionar la densidad y el volumen molar de las diferentes mezclas. Las desviaciones medias relativas en densidad fueron, 0,15, 0,08 y 0,01 %, para a), b) y c), respectivamente; mientras que el caso de volumen molar los valores fueron 1,9, 2,1 y 0,1 %, para a), b) y c), respectivamente.