High Nutrient Concentration Can Induce Virulence Factor Expression and Cause Higher Virulence in an Environmentally Transmitted Pathogen

The plasmodium of Physarum polycephalum is a large single cell visible with the naked eye. When inoculated on a substrate with attractants and repellents the plasmodium develops optimal networks of protoplasmic tubes which span sites of attractants (i.e. nutrients) yet avoid domains with a high nutrient concentration. It should therefore be possible to program the plasmodium towards deterministic adaptive transformation of internalised nano- and micro-scale materials. In laboratory experiments with magnetite nanoparticles and glass micro-spheres coated with silver metal the authors demonstrate that the plasmodium of P. polycephalum can propagate the nano-scale objects using a number of distinct mechanisms including endocytosis, transcytosis and dragging. The results of the authors’ experiments could be used in the development of novel techniques targeted towards the growth of metallised biological wires and hybrid nano- and micro-circuits.

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PERFORMANCE AND CARCASS QUALITY OF BROILER TOM TURKEYS SUBJECTED TO A POST-HATCH FAST AND OFFERED STARTING RATIONS OF DIFFERENT NUTRIENT CONCENTRATION

Canadian Journal of Animal Science ◽

10.4141/cjas78-033 ◽

1978 ◽

Vol 58 (2) ◽

pp. 233-243 ◽

Cited By ~ 11

Author(s):

E. T. MORAN Jr.

Keyword(s):

Crude Protein ◽

Nutrient Concentration ◽

Normal Diet ◽

Carcass Quality ◽

Feed Conversion ◽

High Nutrient ◽

Commercial Source ◽

High Nutrient Concentration ◽

Medium Type

Commercial source, medium-type male poults were either placed in floor pens with food and water within 6 h after hatching or delayed a subsequent 24 h. Starting feed offered in each case was either of a normal (28% crude protein and 2,850 kcal ME/kg) or high (30% and 3,040 kcal) nutrient concentration. During the initial 2 wk, birds that had been fasted gained less weight but had a better feed conversion than those placed early. Poults which received a ration having a high nutrient concentration gained more weight and had a better feed conversion than those offered the normal diet. Mortality at this time was greater with birds subjected to a fast than those placed early. Having access to the higher nutrient concentration ration led to a greater mortaility than if the normal diet was employed. Body weight differences established during the first 2 wk remained throughout the experiment. Feed conversions of rations common to all groups during the subsequent 2- to 6-, 6-to 10- and 10- to 14-wk periods were not influenced by the early treatments after 6 wk of age. Slaughter at 14 wk did not reveal any differences in apparent carcass yield, conformation or finish grade. Degree of fleshing was reduced when poults were subjected to a post-hatch fast and partially improved when the high nutrient starting diet was fed. Effects of fasting and early nutrition on mortality and carcass changes are explained in terms of biochemical events occurring with the neonate.

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Effect of dietary nutrient concentration on the performance of hens beginning lay in early summer

Australian Journal of Experimental Agriculture ◽

10.1071/ea9860405 ◽

1986 ◽

Vol 26 (4) ◽

pp. 405 ◽

Cited By ~ 1

Author(s):

AS Pell ◽

RW Polkinghorne

Keyword(s):

Egg Production ◽

Nutrient Concentration ◽

Early Summer ◽

Nutrient Concentrations ◽

Egg Mass ◽

Meat Meal ◽

High Nutrient ◽

Dietary Nutrient ◽

Metabolisable Energy ◽

High Nutrient Concentration

Hens of 2 laying strains were fed ad libitum from 20 to 72 weeks of age on 3 diets of different nutrient concentration. The start of lay coincided with the onset of the hot summer. During summer, birds on the diet with high nutrient concentration (HNC, 19% protein, 12.6 MJ metabolisable energy (ME)/kg) had significantly higher intakes of ME (3% higher) and other nutrients than did those on the diets of medium (MNC, 18% protein, 11.7 MJ ME/kg) and low (LNC, 16% protein, 11.4 MJ ME/kg) nutrient concentration. Egg weight. egg mass and feed efficiency were greater on the HNC diet than on the MNC and LNC diets. Birds on the HNC diet produced more eggs (10% more) than those on the LNC diet. Over the cooler periods, feed intakes were inversely related to energy level, with no dietary effects on egg production. It is concluded that grain- and meat meal-based diets of low nutrient concentrations are unlikely to support maximum performance in early lay in hot conditions and that increased dietary nutrient concentrations can improve performance via increased nutrient intake.

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Nutrient Concentration and Fruit Thinning Affect Shelf Life of Long English Cucumber

HortScience ◽

10.21273/hortsci.26.10.1299 ◽

1991 ◽

Vol 26 (10) ◽

pp. 1299-1300 ◽

Cited By ~ 11

Author(s):

W.C. Lin ◽

D.L. Ehret

Keyword(s):

Shelf Life ◽

Cucumis Sativus ◽

Nutrient Concentration ◽

Fruit Color ◽

Main Stem ◽

Nutrient Concentrations ◽

Fruit Thinning ◽

High Nutrient ◽

Marketable Fruit ◽

High Nutrient Concentration

Long English cucumber (Cucumis sativus L.) plants were treated with one of three nutrient concentrations in combination with two fruit thinning treatments forming a 3 × 2 factorial greenhouse experiment. High nutrient concentration enhanced fruit color at harvest and prolonged shelf life but reduced marketable fruit per plant. Thinning of one-third of the fruit from the main stem and laterals had a similar effect. Cucumbers harvested from the upper canopy generally had longer shelf life than those from the lower canopy. Shelf life was correlated with fruit color at harvest.

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High nutrient concentration and temperature alleviated formation of large colonies of Microcystis: Evidence from field investigations and laboratory experiments

Water Research ◽

10.1016/j.watres.2016.05.080 ◽

2016 ◽

Vol 101 ◽

pp. 167-175 ◽

Cited By ~ 35

Author(s):

Wei Zhu ◽

Xiaohua Zhou ◽

Huaimin Chen ◽

Li Gao ◽

Man Xiao ◽

...

Keyword(s):

Nutrient Concentration ◽

Laboratory Experiments ◽

Field Investigations ◽

High Nutrient ◽

High Nutrient Concentration

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The Source of Muddy Odor in Bream (Abramis brama) from the Porvoo Sea Area (Gulf of Finland)

Journal of the Fisheries Research Board of Canada ◽

10.1139/f79-126 ◽

1979 ◽

Vol 36 (8) ◽

pp. 883-890 ◽

Cited By ~ 18

Author(s):

Per-Edvin Persson

Keyword(s):

Abramis Brama ◽

Blue Green Alga ◽

Bream Abramis Brama ◽

High Nutrient ◽

Off Flavors ◽

Odor Compounds ◽

High Concentrations ◽

High Nutrient Concentration ◽

Oscillatoria Agardhii ◽

Sea Area

The study area was a shallow, extremely eutrophic, somewhat brackish water bay on the south coast of Finland. Muddy odor in bream (Abramis brama) was significantly correlated with the amount of the blue-green alga Oscillatoria agardhii occurring in the phytoplankton. Cultures dominated by this alga contained the muddy odor compound geosmin. The high concentrations of O. agardhii in the study area were caused by several interacting factors, of which the high nutrient concentration and the temperature of the water seemed to be especially important. Odoriferous actinomycetes isolated from the water produced the muddy odor compounds geosmin and 2-methylisoborneol, but there seemed to be a lag time of several weeks between maximal concentrations of actinomycetes and development of off-flavors in the fish. Key words: geosmin, 2-methylisoborneol, Oscillatoria agardhii, actinomycetes, flavor, fish, eutrophication

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Modulation of Virulence Factor Expression by Pathogen Target Cell Contact

Science ◽

10.1126/science.273.5279.1231 ◽

1996 ◽

Vol 273 (5279) ◽

pp. 1231-1233 ◽

Cited By ~ 288

Author(s):

J. Pettersson ◽

R. Nordfelth ◽

E. Dubinina ◽

T. Bergman ◽

M. Gustafsson ◽

...

Keyword(s):

Virulence Factor ◽

Target Cell ◽

Cell Contact ◽

Factor Expression

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EnterotoxigenicE. colivirulence gene regulation in human infections

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1808982115 ◽

2018 ◽

Vol 115 (38) ◽

pp. E8968-E8976 ◽

Cited By ~ 15

Author(s):

Alexander A. Crofts ◽

Simone M. Giovanetti ◽

Erica J. Rubin ◽

Frédéric M. Poly ◽

Ramiro L. Gutiérrez ◽

...

Keyword(s):

Gene Expression ◽

Virulence Factor ◽

Virulence Gene ◽

Human Infection ◽

Anaerobic Growth ◽

Infection Model ◽

Low Oxygen ◽

Virulence Gene Expression ◽

Factor Expression

EnterotoxigenicEscherichia coli(ETEC) is a global diarrheal pathogen that utilizes adhesins and secreted enterotoxins to cause disease in mammalian hosts. Decades of research on virulence factor regulation in ETEC has revealed a variety of environmental factors that influence gene expression, including bile, pH, bicarbonate, osmolarity, and glucose. However, other hallmarks of the intestinal tract, such as low oxygen availability, have not been examined. Further, determining how ETEC integrates these signals in the complex host environment is challenging. To address this, we characterized ETEC’s response to the human host using samples from a controlled human infection model. We found ETEC senses environmental oxygen to globally influence virulence factor expression via the oxygen-sensitive transcriptional regulator fumarate and nitrate reduction (FNR) regulator. In vitro anaerobic growth replicates the in vivo virulence factor expression profile, and deletion offnrin ETEC strain H10407 results in a significant increase in expression of all classical virulence factors, including the colonization factor antigen I (CFA/I) adhesin operon and both heat-stable and heat-labile enterotoxins. These data depict a model of ETEC infection where FNR activity can globally influence virulence gene expression, and therefore proximity to the oxygenated zone bordering intestinal epithelial cells likely influences ETEC virulence gene expression in vivo. Outside of the host, ETEC biofilms are associated with seasonal ETEC epidemics, and we find FNR is a regulator of biofilm production. Together these data suggest FNR-dependent oxygen sensing in ETEC has implications for human infection inside and outside of the host.

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RocA Regulates Phosphatase Activity of Virulence Sensor CovS of Group A Streptococcus in Growth Phase- and pH-Dependent Manners

mSphere ◽

10.1128/msphere.00361-20 ◽

2020 ◽

Vol 5 (3) ◽

Author(s):

Chuan Chiang-Ni ◽

He-Jing Chiou ◽

Huei-Chuan Tseng ◽

Chih-Yun Hsu ◽

Cheng-Hsun Chiu

Keyword(s):

Stationary Phase ◽

Phosphatase Activity ◽

Virulence Factor ◽

Growth Phase ◽

Exponential Phase ◽

Acidic Stress ◽

Phosphorylation Level ◽

Factor Expression ◽

Group A ◽

Ph Dependent

ABSTRACT The control of the virulence response regulator and sensor (CovR-CovS) two-component regulatory system in group A Streptococcus (GAS) strains regulates more than 15% of gene expression and has critical roles in invasive GAS infection. The membrane-embedded CovS has kinase and phosphatase activities, and both are required for modulating the phosphorylation level of CovR. Regulator of Cov (RocA) is a positive regulator of covR and also been shown to be a pseudokinase that interacts with CovS to enhance the phosphorylation level of CovR; however, how RocA modulates the activity of CovS has not been determined conclusively. Although the phosphorylation level of CovR was decreased in the rocA mutant in the exponential phase, the present study shows that phosphorylated CovR in the rocA mutant increased to levels similar to those in the wild-type strain in the stationary phase of growth. In addition, acidic stress, which is generally present in the stationary phase, enhanced the phosphorylation level of CovR in the rocA mutant. The phosphorylation levels of CovR in the CovS phosphatase-inactivated mutant and its rocA mutant were similar under acidic stress and Mg2+ (the signal that inhibits CovS phosphatase activity) treatments, suggesting that the phosphatase activity, but not the kinase activity, of CovS is required for RocA to modulate CovR phosphorylation. The phosphorylation level of CovR is crucial for GAS strains to regulate virulence factor expression; therefore, the growth phase- and pH-dependent RocA activity would contribute significantly to GAS pathogenesis. IMPORTANCE The emergence of invasive group A streptococcal infections has been reported worldwide. Clinical isolates that have spontaneous mutations or a truncated allele of the rocA gene (e.g., emm3-type isolates) are considered to be more virulent than isolates with the intact rocA gene (e.g., emm1-type isolates). RocA is a positive regulator of covR and has been shown to enhance the phosphorylation level of intracellular CovR regulator through the functional CovS protein. CovS is the membrane-embedded sensor and modulates the phosphorylation level of CovR by its kinase and phosphatase activities. The present study shows that the enhancement of CovR phosphorylation is mediated via the repression of CovS’s phosphatase activity by RocA. In addition, we found that RocA acts dominantly on modulating CovR phosphorylation under neutral pH conditions and in the exponential phase of growth. The phosphorylation level of CovR is crucial for group A Streptococcus species to regulate virulence factor expression and is highly related to bacterial invasiveness; therefore, growth phase- and pH-dependent RocA activity and the sequence polymorphisms of rocA gene would contribute significantly to bacterial phenotype variations and pathogenesis.

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