A new model for the anaerobic fermentation of glycerol in enteric bacteria: trunk and auxiliary pathways in Escherichia coli

Anaerobic fermentation of glycerol in the Enterobacteriaceae family has long been considered a unique property of species that synthesize 1,3-propanediol (1,3-PDO). However, we have discovered that Escherichia coli can ferment glycerol in a 1,3-PDO-independent manner. We identified 1,2-propanediol (1,2-PDO) as a fermentation product and established the pathway that mediates its synthesis as well as its role in the metabolism of glycerol. We also showed that the trunk pathway responsible for the conversion of glycerol into glycolytic intermediates is composed of two enzymes: a type II glycerol dehydrogenase (glyDH-II) and a dihydroxyacetone kinase (DHAK), the former of previously unknown physiological role. Based on our findings, we propose a new model for glycerol fermentation in enteric bacteria in which: (i) the production of 1,2-PDO provides a means to consume reducing equivalents generated in the synthesis of cell mass, thus facilitating redox balance, and (ii) the conversion of glycerol to ethanol, through a redox-balanced pathway, fulfills energy requirements by generating ATP via substrate-level phosphorylation. The activity of the formate hydrogen-lyase and F(0)F(1)-ATPase systems were also found to facilitate the fermentative metabolism of glycerol, and along with the ethanol and 1,2-PDO pathways, were considered auxiliary or enabling. We demonstrated that glycerol fermentation in E. coli was not previously observed due to the use of medium formulations and culture conditions that impair the aforementioned pathways. These include high concentrations of potassium and phosphate, low concentrations of glycerol, alkaline pH, and closed cultivation systems that promote the accumulation of hydrogen gas.     

Fermentation of glycerol and production of valuable chemical and biofuel molecules

Glycerol has attracted the attention of scientific and industrial communities due to its generation in bulk quantities as a byproduct of biofuel industries. With the rapid growth of these industries in recent years, glycerol is frequently treated as a very low-value byproduct or even a waste product with a disposal cost associated to it. Glycerol is not only abundant and inexpensive but also can generate more reducing equivalents than glucose or xylose. This unique characteristic of glycerol offers a tremendous opportunity for its biological conversion to valuable products at higher yield. This review focuses on research efforts to utilize glycerol as a carbon source for the production of a variety of fuels and chemicals by both native and metabolically engineered microorganisms.     

Functional analyses of recombinant mouse hepcidin-1 in cell culture and animal model

Hepcidin is a peptide hormone that plays an important role in iron metabolism. We have produced a recombinant mouse hepcidin-1 by using baculovirus expression system. Its expression yield was 25 μg/ml when cell culture media were supplemented with a protease inhibitor cocktail. The recombinant mouse hepcidin-1 and synthetic human hepcidin-25 had similar effects on reducing ferroportin expression in J774A cell line and in peritoneal macrophages. However, synthetic human hepcidin-25 was more efficient than recombinant mouse hepcidin-1 in reducing iron concentration in blood circulation (p < 0.01).     

Effects of Probiotic Yogurt on Serum Omentin-1, Adropin,and Nesfatin-1 Concentrations in Overweight and Obese Participants Under Low-Calorie Diet

Probiotics and Antimicrobial Proteins - Data on the effects of probiotics on adipokines such as omentin-1, nesfatin-1, and adropin are limited. The aim of this study was to evaluate the effects of...     

Quality control of the parasitoid wasp Trichogramma brassicae(Hymenoptera:Trichogrammatidae)over 45 generations of rearing on Sitotroga cerealella

Trichogramma brassicae(Bezdenko)is an important biological control agent that has been used widely against many lepidopteran pests.Commonly,colonies of Tri-chog...     

DPIV measurements of flow disturbances in stented artery models: adverse affects of compliance mismatch

Vascular stents influence the post-procedural hemodynamic environment in ways that may encourage restenosis. Understanding how stents influence flow patterns may lead to more hemodynamically compatible stent designs that alleviate thrombus formation and promote endothelialization. This study employed time-resolved Digital Particle Image Velocimetry (DPIV) to compare the hemodynamic performance of two stents in a compliant vessel. The first stent was a rigid insert, representing an extreme compliance mismatch. The second stent was a commercially available nitinol stent with some flexural characteristics. DPIV showed that compliance mismatch promotes the formation of a ring vortex in the vicinity of the stent. Larger compliance mismatch increased both the size and residence time of the ring vortex, and introduced in-flow stagnation points. These results provide detailed quantitative evidence of the hemodynamic effect of stent mechanical properties. Better understanding of these characteristics will provide valuable information for modifying stent design in order to promote long-term patency.     

A rapid and non leaky way for preparation of the sharp intracellular recording microelectrodes

To fill microelectrodes using backfilling method needs excessive time approximately 4–6  h. It is often difficult to fill microelectrodes without damage or leakage. A main problem is bubble formation in microelectrodes which has an impact on the electrical properties of the electrode and thus it influences the quality of the recording. Based on Archimede's principle there is a force within a solution which pushes insoluble material with a lower specific gravity upward and outside of the solution. Centrifugation can increase the force to eliminate the bubbles.

We designed a microelectrode holder to protect microelectrode sensitive tips from mechanical damage due to the gravity tensions; it can help to eliminate the bubbles easily and simultaneously in 10  min or less.

The tests were performed for 2000, 4000, and 8000  rpm centrifugation each one for 3, 6 and 12  min duration respectively, it was found that the bubbles were completely eliminated at 8000  rpm for 6–12  min and there were no significant differences for resistance, and the number of leaky or damaged electrodes between the two methods.

In the new design of devices, the materials used and the design of the holder are simple and the approach is applicable to many laboratories worldwide.     

Identification of cultivation condition to produce correctly folded form of a malaria vaccine based on Plasmodium falciparum merozoite surface protein-1 in Escherichia coli

The C-terminal, 19-kDa domain of Plasmodium falciparum merozoite surface protein-1 (PfMSP-1₁₉) is among the leading vaccine candidate for malaria due to its essential role in erythrocyte invasion by the parasite. We designed a synthetic gene for optimal expression of recombinant PfMSP-1₁₉ in Escherichia coli and developed a scalable process to obtain high-quality PfMSP-1₁₉. The synthetic gene construct yielded a fourfold higher expression level of PfMSP-1₁₉ in comparison to the native gene construct. Optimization of cultivation conditions in the bioreactor indicated important role of yeast extract and substrate feeding strategy for obtaining enhanced expression of soluble and correctly folded PfMSP-1₁₉. It was observed that the higher expression level of PfMSP-1₁₉ was essentially associated with the generation of higher level of incorrectly folded PfMSP-1₁₉. A simple purification procedure comprising metal affinity and ion exchange chromatography was developed to purify correctly folded form of PfMSP-1₁₉ from cell lysate. Biochemical and biophysical characterization of purified PfMSP-1₁₉ suggested that it was highly pure, homogeneous, and correctly folded.     

Immune response of macrophages from young and aged mice to the oral pathogenic bacterium <Emphasis Type="Italic">Porphyromonas gingivalis</Emphasis>

Periodontal disease is a chronic inflammatory gum disease that in severe cases leads to tooth loss. Porphyromonas gingivalis (Pg) is a bacterium closely associated with generalized forms of periodontal disease. Clinical onset of generalized periodontal disease commonly presents in individuals over the age of 40. Little is known regarding the effect of aging on inflammation associated with periodontal disease. In the present study we examined the immune response of bone marrow derived macrophages (BMM) from young (2-months) and aged (1-year and 2-years) mice to Pg strain 381. Pg induced robust expression of cytokines; tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10, chemokines; neutrophil chemoattractant protein (KC), macrophage colony stimulating factor (MCP)-1, macrophage inflammatory protein (MIP)-1α and regulated upon activation normal T cell expressed and secreted (RANTES), as well as nitric oxide (NO, measured as nitrite), and prostaglandin E2 (PGE2) from BMM of young mice. BMM from the 2-year age group produced significantly less TNF-α, IL-6 and NO in response to Pg as compared with BMM from 2-months and 1-year of age. We did not observe any difference in the levels of IL-1β, IL-10 and PGE2 produced by BMM in response to Pg. BMM from 2-months and 1-year of age produced similar levels of all chemokines measured with the exception of MCP-1, which was reduced in BMM from 1-year of age. BMM from the 2-year group produced significantly less MCP-1 and MIP-1α compared with 2-months and 1-year age groups. No difference in RANTES production was observed between age groups. Employing a Pg attenuated mutant, deficient in major fimbriae (Pg DPG3), we observed reduced ability of the mutant to stimulate inflammatory mediator expression from BMMs as compared to Pg 381, irrespective of age. Taken together these results support senescence as an important facet of the reduced immunological response observed by BMM of aged host to the periodontal pathogen Pg.     

Incomplete Restoration of Angiotensin II - Induced Renal Extracellular Matrix Deposition and Inflammation Despite Complete Functional Recovery in Rats

Some diseases associated with a temporary deterioration in kidney function and/or development of proteinuria show an apparently complete functional remission once the initiating trigger is removed. While it was earlier thought that a transient impairment of kidney function is harmless, accumulating evidence now suggests that these patients are more prone to developing renal failure later in life. We therefore sought to investigate to what extent renal functional changes, inflammation and collagen deposition are reversible after cessation of disease induction, potentially explaining residual sensitivity to damage. Using a rat model of Angiotensin II (Ang II)-induced hypertensive renal disease we show the development of severe hypertension (212 ± 10.43 vs. 146 ± 1.4 mmHg, p<0.001) and proteinuria (51.4 ± 6.3 vs. 14.7 ± 2.0 mg/24h, p<0.01) with declined creatinine clearance (2.0 ± 0.5 vs. 4.9 ± 0.6 mL/min, p<0.001) to occur after 3 weeks of Ang II infusion. At the structural level, Ang II infusion resulted in interstitial inflammation (18.8 ± 4.8 vs. 3.6 ± 0.5 number of macrophages, p<0.001), renal interstitial collagen deposition and lymphangiogenesis (4.1 ± 0.4 vs. 2.2 ± 0.4 number of lymph vessels, p<0.01). Eight weeks after cessation of Ang II, all clinical parameters, pre-fibrotic changes such as myofibroblast transformation and increase in lymph vessel number (lymphangiogenesis) returned to control values. However, glomerular desmin expression, glomerular and periglomerular macrophages and interstitial collagens remained elevated. These dormant abnormalities indicate that after transient renal function decline, inflammation and collagen deposition may persist despite normalization of the initiating pathophysiological stimulus perhaps rendering the kidney more vulnerable to further damage.