This study investigated the quorum sensing, biofilm and type three secretion system (TTSS) inhibitory properties of citrus flavonoids. Flavonoids were tested for their ability to inhibit quorum ...sensing using Vibrio harveyi reporter assay. Biofilm assays were carried out in 96-well plates. Inhibition of biofilm formation in Escherichia coli O157:H7 and V. harveyi by citrus flavonoids was measured. Furthermore, effect of naringenin on expression of V. harveyi TTSS was investigated by semi-quantitative PCR. Differential responses for different flavonoids were observed for different cell-cell signalling systems. Among the tested flavonoids, naringenin, kaempferol, quercetin and apigenin were effective antagonists of cell-cell signalling. Furthermore, these flavonoids suppressed the biofilm formation in V. harveyi and E. coli O157:H7. In addition, naringenin altered the expression of genes encoding TTSS in V. harveyi. The results of the study indicate a potential modulation of bacterial cell-cell communication, E. coli O157:H7 biofilm and V. harveyi virulence, by flavonoids especially naringenin, quercetin, sinensetin and apigenin. Among the tested flavonoids, naringenin emerged as potent and possibly a nonspecific inhibitor of autoinducer-mediated cell-cell signalling. Naringenin and other flavonoids are prominent secondary metabolites present in citrus species. Therefore, citrus, being a major source of some of these flavonoids and by virtue of widely consumed fruit, may modulate the intestinal microflora. Currently, a limited number of naturally occurring compounds have demonstrated their potential in inhibition of cell-cell communications; therefore, citrus flavonoids may be useful as lead compounds for the development of antipathogenic agents.
Aims
Acid exposure induces accumulation of certain metabolites in bacteria. The experimental objective was to identify the primary metabolites accumulating in Escherichia coli O26:H11 as a function ...of acid (pH 3·6) exposure.
Methods and Results
Different buffers of pH 7·5 and 3·6 were used to study the metabolites accumulating in E. coli O26:H11 cells during such pH exposure. After 24 h of acid exposure, there was a 7‐log decline in E. coli populations on trypticase soy agar plates. Untargeted metabolomic analysis identified 293 primary metabolites of which 145 metabolites were differentially (P < 0·01) accumulating between pH 7·5 and 3·6 in E. coli O26:H11.
Conclusions
After 24 h of acid exposure, 21 different metabolic pathways appeared to be functional, suggesting that the cells were still metabolically active. Among the identifiable pathways, the key differentially expressed pathways were associated with peptidoglycan biosynthesis, purine metabolism, d‐Glutamine/d‐glutamate metabolism, nitrogen metabolism, unsaturated fatty acid biosynthesis and inositol phosphate metabolism.
Significance and Impact of the Study
Shiga toxin producing non‐O157 E. coli strains such as E. coli O26 are responsible for a growing number of food‐related illnesses in the United States and around the world. From food production to consumption, micro‐organisms in foods experience dramatic pH fluctuations by organic acids introduced either during food processing or by inorganic acids in the stomach. Acid exposure induces specific metabolite accumulation in bacterial cells. Understanding the survival mechanisms of pathogenic micro‐organisms by studying the metabolome would be helpful in introducing effective hurdles and thus ensuring food safety.
MONSOON MISSION Rao, Suryachandra A.; Goswami, B. N.; Sahai, A. K. ...
Bulletin of the American Meteorological Society,
12/2019, Volume:
100, Issue:
12
Journal Article
Peer reviewed
Open access
In spite of the summer monsoon’s importance in determining the life and economy of an agriculture-dependent country like India, committed efforts toward improving its prediction and simulation have ...been limited. Hence, a focused mission mode program Monsoon Mission (MM) was founded in 2012 to spur progress in this direction. This article explains the efforts made by the Earth System Science Organization (ESSO), Ministry of Earth Sciences (MoES), Government of India, in implementing MM to develop a dynamical prediction framework to improve monsoon prediction. Climate Forecast System, version 2 (CFSv2), and the Met Office Unified Model (UM) were chosen as the base models. The efforts in this program have resulted in 1) unparalleled skill of 0.63 for seasonal prediction of the Indian monsoon (for the period 1981–2010) in a high-resolution (~38 km) seasonal prediction system, relative to present-generation seasonal prediction models; 2) extended-range predictions by a CFS-based grand multimodel ensemble (MME) prediction system; and 3) a gain of 2-day lead time from very high-resolution (12.5 km) Global Forecast System (GFS)-based short-range predictions up to 10 days. These prediction skills are on par with other global leading weather and climate centers, and are better in some areas. Several developmental activities like coupled data assimilation, changes in convective parameterization, cloud microphysics schemes, and parameterization of land surface processes (including snow and sea ice) led to the improvements such as reducing the strong model biases in the Indian summer monsoon simulation and elsewhere in the tropics.
Aims/hypothesis We have previously described a strong correlation between pyruvate cycling and insulin secretion. We have also demonstrated a particularly important role for a pyruvate-isocitrate ...cycling pathway involving the mitochondrial citrate/isocitrate carrier (CIC) and cytosolic NADP-dependent isocitrate dehydrogenase. CIC requires cytosolic malate as a counter-substrate during citrate and isocitrate export. Thus, considering that the mitochondrial dicarboxylate carrier (DIC) provides an important source of cytosolic malate, we investigated the potential role of DIC in control of glucose-stimulated insulin secretion (GSIS). Methods We used pharmacological and small interfering RNA (siRNA) tools to assess the role of DIC in insulin release in clonal insulin-secreting 832/13 cells and isolated rat islets. Results Butylmalonate, an inhibitor of malate transport, reduced cytosolic malate and citrate levels, and inhibited GSIS in a dose-dependent manner in 832/13 cells. Suppression of DIC expression resulted in inhibition of GSIS by 5% to 69%, the extent of inhibition of insulin secretion being proportional to the level of Dic (also known as Slc25a10) gene knockdown. The most effective siRNA duplex against Dic did not affect glucose utilisation, glucose oxidation or ATP/ADP ratio, but did suppress glucose-induced increments of the NADPH/NADP⁺ ratio. Confirmation of our results in primary cultures of isolated rat islets showed that butylmalonate and an adenovirus expressing an siRNA against Dic-inhibited GSIS. Conclusions/interpretation Malate transport by DIC may play an important role in GSIS, possibly by providing cytosolic malate as a counter-substrate for citrate and/or isocitrate export by CIC. These studies also suggest that malate transport by DIC is (1) a critical component of NADPH production mediated by pyruvate-cycling and (2) regulates GSIS.
In a 3-year longitudinal study, we examined the relationship between the seasonal prevalence of antimicrobial-resistant (AR) Escherichia coli isolates from human wastewater and swine fecal samples ...and the following risk factors: the host species, the production type (swine), the vocation (human swine workers, non-swine workers, and slaughter plant workers), and the season, in a multisite, vertically integrated swine and human population representative of a closed agri-food system. Human and swine E. coli (n = 4,048 and 3,429, respectively) isolates from wastewater and fecal samples were tested for antimicrobial susceptibility, using the Sensititre broth microdilution system. There were significant (P < 0.05) differences among AR E. coli prevalence levels of (i) the host species, in which swine isolates were at higher risk for resistance to tetracycline, kanamycin, ceftiofur, gentamicin, streptomycin, chloramphenicol, sulfisoxazole, and ampicillin; (ii) the swine production group, in which purchased boars, nursery piglets, and breeding boars isolates had a higher risk of resistance to streptomycin and tetracycline; and iii) the vocation cohorts, in which swine worker cohort isolates exhibited lower sulfisoxazole and cefoxitin prevalence than the non-swine worker cohorts, while the slaughter plant worker cohort isolates exhibited elevated cefoxitin prevalence compared to that of non-swine workers. While a high variability was observed among seasonal samples over the 3-year period, no significant temporal trends were apparent. There were significant differences in the prevalence levels of multidrug-resistant isolates between host species, with swine at a higher risk of carrying multidrug-resistant strains than humans. Considering vocation, slaughter plant workers were at higher risk of exhibiting multidrug-resistant E. coli than non-swine workers.
Autoinducer-2 (AI-2) is a compound that plays a key role in bacterial cell-to-cell communication (quorum sensing). Previous research has shown certain food matrices inhibit this signaling compound. ...Using the reporter strain, Vibrio harveyi BB170, quorum-sensing inhibitors contained in poultry meat wash (PMW) samples were characterized by molecular weight and hydrophobic properties using liquid chromatography systems. Most fractions that demonstrated AI-2 inhibition were 13.7 kDa or less, and had hydrophobic properties. Hexane was used to extract inhibitory compounds from a PMW preparation and the extract was further separated by gas chromatography (GC). Several fatty acids were identified and quantified. Linoleic acid, oleic acid, palmitic acid, and stearic acid were each tested for inhibition at 0.1, 1, and 10 mM concentrations. All samples expressed AI-2 inhibition (ranging from approximately 25% to 99%). Fatty acids, combined in concentrations equivalent to those determined by GC analysis, expressed inhibition at 59.5%, but higher combined concentrations (10- and 100-fold) had inhibition at 84.4% and 69.5%, respectively. The combined fatty acids (100-fold) did not demonstrate a substantial decrease in colony plate counts, despite presenting high AI-2 inhibition. These fatty acids, through modulating quorum sensing by inhibition, may offer a unique means to control foodborne pathogens and reduce microbial spoilage.
Bacterial cell-to-cell communication is mediated by autoinducer (AI) molecules such as AI-2 and has been reported to regulate gene expression in Escherichia coli O157:H7. We have previously shown ...that ground beef contains compounds that can inhibit sensing of AI-2 like activity. The hypothesis of this study was that AI-2 activity observed in conditioned medium (CM) will enhance E. coli O157:H7 survival and expression of virulence genes, whereas compounds inhibitory (such as those present in ground beef extracts) to AI-2 activity will negate these effects. E. coli O157:H7 luxS mutant strain VS 94 (incapable of synthesizing AI-2) was employed in these studies. The survival of this enteric bacterial pathogen as a function of AI-2 activity and the presence of AI-2 inhibitory compounds was studied at 4 °C. The number of survivors in the presence of AI-2 was significantly higher compared to the absence of AI-2, and the addition of ground beef extracts to conditioned medium negated the influence of AI-2 activity. Autoinducer AI-2 upregulated selected genes virulence genes (yadK, and hha), whereas the ground beef extract reversed the effect of AI-2 on the expression of the selected genes.
Animal feed may serve as a carrier for a wide variety of microorganisms. The primary mode of inoculation of feed materials is the transference of soil by wind, rain, mechanical agitation, or insects ...to standing crops. Some of the microorganisms are adapted to the desiccated and relatively nutrient-poor conditions in soil and survive in similar niches on growing crops. Gastrointestinal pathogens can also introduced into the food chain by animals defecating in the farm environment or by fertilization of crops with manures. Other microorganisms are introduced during storage. In general, the amount of available water in the feed matrix determines whether a microorganism will grow or survive. Some microorganisms, primarily moulds, are adapted to the low amount of available moisture and grow actively within stored seeds and grains. Others will produce spores or enter survival state until the moisture is high enough for bacterial action. There are numerous ways contaminating microorganisms can affect feed quality negatively including reducing dry matter and nutrients, causing musty or sour odours, causing caking of the feed and producing toxins. Finally, feed can act as a carrier for animal and human pathogens. The type of feed, processing treatments and storage conditions can all be factors that influence the population levels and types of microorganisms present. The incidence and variation in the microflora found in animal feed and feed materials are reviewed. A select number of important human and animal pathogens are discussed. Finally there is a brief overview over the detection, surveillance and management strategies of microbial contamination in feed and feed materials.
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