Oxidative phosphorylation supported by an alternative respiratory pathway in mitochondria from Euglena

AbstractThe effect of antimycin, myxothiazol, 2-heptyl-4-hydroxyquinoline-N-oxide, stigmatellin and cyanide on respiration, ATP synthesis, cytochrome c reductase, and membrane potential in mitochondria isolated from dark-grown Euglena cells was determined. With L-lactate as substrate, ATP synthesis was partially inhibited by antimycin, but the other four inhibitors completely abolished the process. Cyanide also inhibited the antimycin-resistant ATP synthesis. Membrane potential was collapsed (<60 mV) by cyanide and stigmatellin. However, in the presence of antimycin, a H+ gradient (>60 mV) that sufficed to drive ATP synthesis remained. Cytochrome c reductase, with L-lactate as donor, was diminished by antimycin and myxothiazol. Cytochrome bc1 complex activity was fully inhibited by antimycin, but it was resistant to myxothiazol. Stigmatellin inhibited both L-lactate-dependent cytochrome c reductase and cytochrome bc1 complex activities. Respiration was partially inhibited by the five inhibitors. The cyanide-resistant respiration was strongly inhibited by diphenylamine, n-propyl-gallate, salicylhydroxamic acid and disulfiram. Based on these results, a model of the respiratory chain of Euglena mitochondria is proposed, in which a quinol-cytochrome c oxidoreductase resistant to antimycin, and a quinol oxidase resistant to antimycin and cyanide are included

Probiotics and Prebiotics as a Therapeutic Strategy to Improve Memory in a Model of Middle-Aged Rats

Aging is associated with morphological, physiological and metabolic changes, leading to multiorgan degenerative pathologies, such as cognitive function decline. It has been suggested that memory loss also involves a decrease in neurotrophic factors, including brain-derived neurotrophic factor (BDNF). In recent years, microbiota has been proposed as an essential player in brain development, as it is believed to activate BDNF secretion through butyrate production. Thus, microbiota modulation by supplementation with probiotics and prebiotics may impact cognitive decline. This study aimed to evaluate the effects of probiotics and prebiotics supplementation on the memory of middle-aged rats. Sprague-Dawley male rats were randomized in four groups (n = 13 per group): control (water), probiotic (E. faecium), prebiotic (agave inulin), symbiotic (E. faecium + inulin), which were administered for 5 weeks by oral gavage. Spatial and associative memory was analyzed using the Morris Water Maze (MWM) and Pavlovian autoshaping tests, respectively. Hippocampus was obtained to analyze cytokines [interleukin (IL-1β) and tumor necrosis factor (TNF-α)], BDNF and γ-aminobutyric acid (GABA) by enzyme-linked immunosorbent assay (ELISA). Butyrate concentrations were also evaluated in feces. The symbiotic group showed a significantly better performance in MWM (p &lt; 0.01), but not in Pavlovian autoshaping test. It also showed significantly lower concentrations of pro-inflammatory cytokines (p &lt; 0.01) and the reduction in IL-1β correlated with a better performance of the symbiotic group in MWM (p &lt; 0.05). Symbiotic group also showed the highest BDNF and butyrate levels (p &lt; 0.0001). Finally, we compared the electrophysiological responses of control (n = 8) and symbiotic (n = 8) groups. Passive properties of CA1 pyramidal cells (PCs) exhibited changes in response to the symbiotic treatment. Likewise, this group showed an increase in the N-methyl-D-aspartate receptor (NMDA)/AMPA ratio and exhibited robust long-term potentiation (LTP; p &lt; 0.01). Integrated results suggest that symbiotics could improve age-related impaired memory

Activation of methane synthesis by cadmium.

<p>(A) 1, 10 and 100 µM of CdCl₂ were added and methane production was determined after 5 min in acetate-grown control cells. (B) Short-term methane synthesis in the absence (open symbols) or presence (filled symbols) of 10 µM CdCl₂ in methanol- (▪) and acetate-grown cells (•). These experiments were started after thoroughly purging the flasks and adding the indicated CdCl₂ concentrations (time-point equal to zero). (C) Activation of methane synthesis by other heavy metals. Acetate-grown cells cultures were incubated for 5 min in the absence or presence of 100 µM of the metals indicated. At t = 0 (before metal addition), the methane remaining in the bottle cultures was 8.8±1.2 µmol methane <i>per</i> culture. P<0.05 using the Student's t-test for non-paired samples for ^a<i>vs</i> control (without cadmium or other metal ion); ^b<i>vs</i> cells exposed to 1 µM cadmium; ^c<i>vs</i> methanol cultures exposed to cadmium.</p

Activation of Methanogenesis by Cadmium in the Marine Archaeon <em>Methanosarcina acetivorans</em>

<div><p><em>Methanosarcina acetivorans</em> was cultured in the presence of CdCl₂ to determine the metal effect on cell growth and biogas production. With methanol as substrate, cell growth and methane synthesis were not altered by cadmium, whereas with acetate, cadmium slightly increased both, growth and methane rate synthesis. In cultures metabolically active, incubations for short-term (minutes) with 10 µM total cadmium increased the methanogenesis rate by 6 and 9 folds in methanol- and acetate-grown cells, respectively. Cobalt and zinc but not copper or iron also activated the methane production rate. Methanogenic carbonic anhydrase and acetate kinase were directly activated by cadmium. Indeed, cells cultured in 100 µM total cadmium removed 41–69% of the heavy metal from the culture and accumulated 231–539 nmol Cd/mg cell protein. This is the first report showing that (i) Cd²⁺ has an activating effect on methanogenesis, a biotechnological relevant process in the bio-fuels field; and (ii) a methanogenic archaea is able to remove a heavy metal from aquatic environments.</p> </div

Methane production and cadmium accumulation in <i>M. acetivorans</i> cultured on acetate or methanol.

<p>Data shown were obtained from cell cultures at the end of the growth curve. Values are the mean ± SD of at least 4 cultures from different batches.</p>a<p>: P<0.05 <i>vs</i> acetate-grown cells at any other concentration of cadmium;</p>b<p>: P<0.05 <i>vs</i> methanol-grown cells at any other concentration of cadmium;</p>c<p>acetate-grown cells <i>vs</i> 25, 50 and 100 µM cadmium, using the Student's t-test.</p

Growth curves and methane synthesis of <i>M. acetivorans</i> cultured on methanol (A, C) or acetate (B, D), respectively, and in the absence (filled squares) or presence of 100 µM CdCl₂ (open squares).

<p>Values represent the mean ± SD of at least 4 different cell batches. ^a: P<0.05 <i>vs</i> control curve without cadmium using two way ANOVA. Inset; curves with 1 (filled circles), 10 (filled triangles), 25 (open squares) and 50 (open circles) µM CdCl₂.</p