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The six-component maintenance of lipid asymmetry (Mla) system is responsible for retrograde transport of phospholipids, ensuring the barrier function of the Gram-negative cell envelope. Located within the outer membrane, MlaA (VacJ) acts as a channel to shuttle phospholipids from the outer leaflet. We identified Neisseria gonorrhoeae MlaA (ngo2121) during high-throughput proteomic mining for potential therapeutic targets against this medically important human pathogen. Our follow-up phenotypic microarrays revealed that lack of MlaA results in a complex sensitivity phenome. Herein we focused on MlaA function in cell envelope biogenesis and pathogenesis. We demonstrate the existence of two MlaA classes among 21 bacterial species, characterized by the presence or lack of a lipoprotein signal peptide. Purified truncated N. gonorrhoeae MlaA elicited antibodies that cross-reacted with a panel of different Neisseria. Little is known about MlaA expression; we provide the first evidence that MlaA levels increase in stationary phase and under anaerobiosis but decrease during iron starvation. Lack of MlaA resulted in higher cell counts during conditions mimicking different host niches; however, it also significantly decreased colony size. Antimicrobial peptides such as polymyxin B exacerbated the size difference while human defensin was detrimental to mutant viability. Consistent with the proposed role of MlaA in vesicle biogenesis, the ΔmlaA mutant released 1.7-fold more membrane vesicles. Comparative proteomics of cell envelopes and native membrane vesicles derived from ΔmlaA and wild type bacteria revealed enrichment of TadA–which recodes proteins through mRNA editing–as well as increased levels of adhesins and virulence factors. MlaA-deficient gonococci significantly outcompeted (up to 16-fold) wild-type bacteria in the murine lower genital tract, suggesting the growth advantage or increased expression of virulence factors afforded by inactivation of mlaA is advantageous in vivo. Based on these results, we propose N. gonorrhoeae restricts MlaA levels to modulate cell envelope homeostasis and fine-tune virulence. [ABSTRACT FROM AUTHOR]

Background: Hepatic steatosis is a major risk factor for graft failure in liver transplantation. Hepatic steatosis shows a greater negative influence on graft function following prolonged cold ischaemia. As the impact of steatosis on hepatocyte metabolism during extended cold ischaemia is not well-described, we compared markers of metabolic capacity and mitochondrial function in steatotic and lean livers following clinically relevant durations of cold preservation. Methods: Livers from 10-week old leptin-deficient obese (ob/ob, n = 9) and lean C57 mice (n = 9) were preserved in ice-cold University of Wisconsin solution. Liver mitochondrial function was then assessed using high resolution respirometry after 1.5, 3, 5, 8, 12, 16 and 24 hours of storage. Metabolic marker enzymes for anaerobiosis and mitochondrial mass were also measured in conjunction with non-bicarbonate tissue pH buffering capacity. Results: Ob/ob and lean mice livers showed severe (>60%) macrovesicular and mild (<30%) microvesicular steatosis on Oil Red O staining, respectively. Ob/ob livers had lower baseline enzymatic complex I activity but similar adenosine triphosphate (ATP) levels compared to lean livers. During cold storage, the respiratory control ratio and complex I-fueled phosphorylation deteriorated approximately twice as fast in ob/ob livers compared to lean livers. Ob/ob livers also demonstrated decreased ATP production capacities at all time-points analyzed compared to lean livers. Ob/ob liver baseline lactate dehydrogenase activities and intrinsic non-bicarbonate buffering capacities were depressed by 60% and 40%, respectively compared to lean livers. Conclusions: Steatotic livers have impaired baseline aerobic and anaerobic capacities compared to lean livers, and mitochondrial function indices decrease particularly from after 5 hours of cold preservation. These data provide a mechanistic basis for the clinical recommendation of shorter cold storage durations in steatotic donor livers. [ABSTRACT FROM AUTHOR]

Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment. [ABSTRACT FROM AUTHOR]

Abstract: Microbial fermentation is a potentially important member of a diverse portfolio of methods available for renewable production of hydrogen using biomass as a substrate. A major factor currently limiting commercial viability of fermentative hydrogen production is poor stoichiometric yield per mole of sugar and end-product feedback inhibition. Although several approaches have been tried to enhance microbial hydrogen productivity, genetic engineering technologies for most promising microorganisms are either unavailable or severely limited. Further efforts to overcome existing issues will need to rely on the ability to analyze, predict and engineer microbial metabolism in native H2-producing strains as well as genetically engineerable strains with constructed H2-metabolism. A shift in the type of biomass substrate from starch-based food crops to ligno-cellulosic crops and wastes that are economically and environmentally less costly to produce, yet more difficult to chemically and biologically process, presents technical challenges that are shared by all emerging biofuel technologies. A brief overview of the current status of fermentative H2-production, including a discussion of directly and indirectly related emerging technologies, is presented. [Copyright &y& Elsevier]

We report the synthesis and X-ray crystal structures of a series of pyridyl ureas of the type currently topical in anion binding and supramolecular gelation applications, along with their anion-binding ability in solution. The structures of the simple pyridyl ureas are dominated by urea···N(pyridyl) hydrogen bonding, because of steric congestion of the urea carbonyl by intramolecular CH···O interations. However, introducing a further competing synthon in the form of alkenic or π-stacking interactions causes a gradual changeover, through a number of interesting intermediate hydrogen bonding motifs, to the urea α-tape arrangement. [ABSTRACT FROM AUTHOR]

Abstract: In fungi, the velvet gene, or veA, is involved in the regulation of diverse cellular processes, including control of asexual and sexual development as well as secondary metabolism. This global regulator is conserved in numerous fungal species. Interestingly, in Aspergilli, where most of the studies on veA have been carried out, this gene has been described to mediate development in response to light. In recent years the knowledge of this important regulatory system has expanded through the use of Aspergillus nidulans as a model organism, and through the study of veA orthologs across fungal genera. This review includes information on the current understanding of veA function and its mechanism of action. The fact that veA has only been found in fungi, together with advances in the elucidation of the veA mechanism, might be useful in designing future control strategies to decrease the detrimental effects of fungi while enhancing those qualities that are beneficial. [Copyright &y& Elsevier]

Abstract: The posterior cingulate cortex (PCC) is the brain region displaying the earliest sign of energy hypometabolism in patients with amnestic mild cognitive impairment (MCI) who develop Alzheimer’s disease (AD). In particular, the activity of the mitochondrial respiratory enzyme cytochrome oxidase (C.O.) is selectively inhibited within the PCC in AD. The present study is the first experimental analysis designed to model in animals the localized cortical C.O. inhibition found as the earliest metabolic sign of early-stage AD in human neuroimaging studies. Rats were used to model local inhibition of C.O. by direct injection of the C.O. inhibitor sodium azide into the PCC. Learning and memory were examined in a spatial holeboard task and brains were analyzed using quantitative histochemical, morphological and biochemical techniques. Behavioral results showed that sodium azide-treated rats were impaired in their memory of the baited pattern in probe trials as compared to their training scores before treatment, without non-specific behavioral differences. Brain analyses showed that C.O. inhibition was specific to the PCC, and sodium azide increased lipid peroxidation, gliosis and neuron loss, and lead to a network functional disconnection between the PCC and interconnected hippocampal regions. It was concluded that impaired memory by local C.O. inhibition in the PCC may serve to model in animals a metabolic lesion similar to that found in patients with amnestic MCI and early-stage AD. This model may be useful as an in vivo testing platform to investigate neuroprotective strategies to prevent or reduce the amnestic effects produced by posterior cingulate energy hypometabolism. [Copyright &y& Elsevier]

Abnormal neuronal signaling caused by metabolic changes characterizes several neurological disorders, and in some instances metabolic interventions provide therapeutic benefits. Indeed, altering metabolism either by fasting or by maintaining a low-carbohydrate (ketogenic) diet might reduce epileptic seizures and offer neuroprotection in part because the diet increases mitochondrial biogenesis and brain energy levels. Here we focus on a novel hypothesis that a ketogenic diet-induced change in energy metabolism increases levels of ATP and adenosine, purines that are critically involved in neuron–glia interactions, neuromodulation and synaptic plasticity. Enhancing brain bioenergetics (ATP) and increasing levels of adenosine, an endogenous anticonvulsant and neuroprotective molecule, might help with understanding and treating a variety of neurological disorders. [Copyright &y& Elsevier]

There are two distinctly different pathways for the catabolism ofl-rhamnose in microorganisms. One pathway with phosphorylated intermediates was described in bacteria; here the enzymes and the corresponding gene sequences are known. The other pathway has no phosphorylated intermediates and has only been described in eukaryotic microorganisms. For this pathway, the enzyme activities have been described but not the corresponding gene sequences. The first enzyme in this catabolic pathway is the NAD-utilizingl-rhamnose 1-dehydrogenase. The enzyme was purified from the yeast Pichia stipitis, and the mass of its tryptic peptides was determined using MALDI-TOF MS. This enabled the identification of the corresponding gene, RHA1. It codes for a protein with 258 amino acids belonging to the protein family of short-chain alcohol dehydrogenases. The ORF was expressed in Saccharomyces cerevisiae. As the gene contained a CUG codon that codes for serine in P. stipitis but for leucine in S. cerevisiae, this codon has changed so that the same amino acid was expressed in S. cerevisiae. The heterologous protein showed the highest activity and affinity withl-rhamnose and a lower activity and affinity withl-mannose andl-lyxose. The enzyme was specific for NAD. A northern blot analysis revealed that transcription in P. stipitis is induced during growth onl-rhamnose but not on other carbon sources. [ABSTRACT FROM AUTHOR]

Abstract: The carcinogen and mutagen, 1-aminoanthracene, was efficiently metabolized by the fungal strain Beauveria bassiana ATCC 7159 to yield three new metabolites identified as 1-acetamido-5-[(4′-O-methyl-β-d-glucopyranosyl)oxy]anthracene, 1-acetamido-8-[(4′-O-methyl-β-d-glucopyranosyl)oxy]anthraquinone, and 1-acetamido-6-[(4′-O-methyl-β-d-glucopyranosyl)oxy]anthraquinone, together with 1-acetamidoanthracene and 1-acetamidoanthraquinone. Formation of these metabolites suggests that the metabolic pathways of 1-aminoanthracene in B. bassiana ATCC 7159 involve acetylation, oxidation, hydroxylation, and O-methylglucosylation. [Copyright &y& Elsevier]

Abstract: Catalase (CAT; EC 1.11.1.6) isolated from leaves of the halophytic plant Mesembryanthemum crystallinum is characterized by a high apparent molecular mass of about 320kDa, and high resistance to denaturing agents (10% ME). SDS-treatment breaks active oligomeric CAT into the less active and putatively dimeric form of 160kDa apparent molecular mass. Three subunits are resolved after denaturing PAGE: 79, 74 and 62kDa. Higher molecular masses of subunits coincide with increased activity of CAT. M. crystallinum leaf CAT reveals a diel variation in the resistance to denaturing factors and the stability of CAT is increased in a light-dependent manner both in C3- and in CAM-induced plants. Unchanged level of leaf CAT transcripts is documented in the diurnal cycle of C3 plants and after salinity-induced crassulacean acid metabolism (CAM). [Copyright &y& Elsevier]

Abstract: Uridine, the major circulating pyrimidine nucleoside, participating in the regulation of a number of physiological processes, is readily uptaken into mammalian cells. The balance between anabolism and catabolism of intracellular uridine is maintained by uridine kinase, catalyzing the first step of UTP and CTP salvage synthesis, and uridine phosphorylase, catalyzing the first step of uridine degradation to β-alanine in liver. In the present study we report that the two enzymes have an additional role in the homeostatic regulation of purine and pyrimidine metabolism in brain, which relies on the salvage synthesis of nucleotides from preformed nucleosides and nucleobases, rather than on the de novo synthesis from simple precursors. The experiments were performed in rat brain extracts and cultured human astrocytoma cells. The rationale of the reciprocal regulation of purine and pyrimidine salvage synthesis in brain stands (i) on the inhibition exerted by UTP and CTP, the final products of the pyrimidine salvage pathway, on uridine kinase and (ii) on the widely accepted idea that pyrimidine salvage occurs at the nucleoside level (mostly uridine), while purine salvage is a 5-phosphoribosyl-1-pyrophosphate (PRPP)-mediated process, occurring at the nucleobase level. Thus, at relatively low UTP and CTP level, uptaken uridine is mainly anabolized to uridine nucleotides. On the contrary, at relatively high UTP and CTP levels the inhibition of uridine kinase channels uridine towards phosphorolysis. The ribose-1-phosphate is then transformed into PRPP, which is used for purine salvage synthesis. [Copyright &y& Elsevier]

To satisfy the minimal requirements for life, an information carrying molecular structure must be able to convert resources into building blocks and also be able to adapt to or modify its environment to enhance its own proliferation. Furthermore, new copies of itself must have variable fitness such that evolution is possible. In practical terms, a minimal protocell should be characterized by a strong coupling between its metabolism and genetic subsystem, which is made possible by the container. There is still no general agreement on how such a complex system might have been naturally selected for in a prebiotic environment. However, the historical details are not important for our investigations as they are related to assembling and evolution of protocells in the laboratory. Here, we study three different minimal protocell models of increasing complexity, all of them incorporating the coupling between a ‘genetic template’, a container and, eventually, a toy metabolism. We show that for any local growth law associated with template self-replication, the overall temporal evolution of all protocell's components follows an exponential growth (efficient or uninhibited autocatalysis). Thus, such a system attains exponential growth through coordinated catalytic growth of its component subsystems, independent of the replication efficiency of the involved subsystems. As exponential growth implies the survival of the fittest in a competitive environment, these results suggest that protocell assemblies could be efficient vehicles in terms of evolving through Darwinian selection. [ABSTRACT FROM AUTHOR]

Many regard metabolism as one of the central phenomena (or criteria) of life. Yet, the earliest infrabiological systems may have been devoid of metabolism: such systems would have been extreme heterotrophs. We do not know what level of complexity is attainable for chemical systems without enzymatic aid. Lack of template-instructed enzymatic catalysis may put a ceiling on complexity owing to inevitable spontaneous decay and wear and tear of chemodynamical machines. Views on the origin of metabolism critically depend on the assumptions concerning the sites of synthesis and consumption of organic compounds. If these sites are different, non-enzymatic origin of autotrophy is excluded. Whether autotrophy is secondary or not, it seems that protocell boundaries may have become more selective with time, concurrent with the enzymatization of the metabolic network. Primary heterotrophy and autotrophy imply pathway innovation and retention, respectively. The idea of metabolism–membrane coevolution leads to a scenario of progressive sequestration of the emerging living system from its exterior milieu. Comparative data on current protein enzymes may shed some light on such a primeval process by analogy, since two main ideas about enzymatization (the retroevolution and the patchwork scenarios) may not necessarily be mutually exclusive and the earliest enzymatic system may have used ribozymes rather than proteins. [ABSTRACT FROM AUTHOR]

Abstract: Studies have proposed the involvement of oxidative stress and neuronal energy dysfunctions in the pathophysiology of bipolar disorder (BD). This study evaluates plasma levels of the oxidative/energy metabolism markers, thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), and neuron-specific enolase (NSE) during initial episodes of mania compared to controls in 75 subjects. Two groups of manic subjects (unmedicated n =30, and lithium-treated n =15) were age/gender matched with healthy controls (n =30). TBARS and antioxidant enzymes activity (SOD and CAT) were increased in unmedicated manic patients compared to controls. Conversely, plasma NSE levels were lower during mania than in the controls. In contrast, acute treatment with lithium showed a significant reduction in both SOD/CAT ratio and TBARS levels. These results suggest that initial manic episodes are associated with both increased oxidative stress parameters and activated antioxidant defenses, which may be related to dysfunctions on energy metabolism and neuroplasticity pathways. Antioxidant effects using lithium in mania were shown, and further studies are necessary to evaluate the potential role of these effects in the pathophysiology and therapeutics of BD. [Copyright &y& Elsevier]

Abstract: Freshwater turtles of the Trachemys and Chrysemys genera are champion facultative anaerobes able to survive for several months without oxygen during winter hibernation in cold water. They have been widely used as models to identify and understand the molecular mechanisms of natural anoxia tolerance and the molecular basis of the hypoxic/ischemic injuries that occur in oxygen-sensitive systems and underlie medical problems such as heart attack and stroke. Peter L. Lutz spent much of his career investigating turtle anaerobiosis with a particular focus on the mechanisms of brain ion homeostasis and neurotransmitter responses to anoxia exposure and the mechanisms that suppress brain ion channel function and neuronal excitability during anaerobiosis. Our interests intersected over the mechanisms of metabolic rate depression which is key to long term anoxia survival. Studies in my lab have shown that a key mechanism of metabolic arrest is reversible protein phosphorylation which provides coordinated suppression of the rates of multiple ATP-producing, ATP-utilizing and related cellular processes to allow organisms to enter a stable hypometabolic state. Anoxia tolerance is also supported by selective gene expression as revealed by recent studies using cDNA library and DNA array screening. New studies with both adult T. scripta elegans and hatchling C. picta marginata have identified prominent groups of genes that are up-regulated under anoxia in turtle organs, in several cases suggesting aspects of cell function and metabolic regulation that have not previously been associated with anaerobiosis. These groups of anoxia-responsive genes include mitochondrially-encoded subunits of electron transport chain proteins, iron storage proteins, antioxidant enzymes, serine protease inhibitors, transmembrane solute carriers, neurotransmitter receptors and transporters, and shock proteins. [Copyright &y& Elsevier]

This review is a logical development of a previous publication, which summarized the main results of the early period of the systematic and active studying of hypoxic and anoxic stresses in plants. These studies laid a foundation for a new scientific discipline in biology, the investigation relevant to plant anaerobic stress. This review considers a further development of this trend when the investigations embraced a wider set of topics and the discipline acquired an international recognition. The results obtained during last decades by physiologists, biochemists, and molecular biologists engaged in the problem of plant anaerobic stress confirmed the correctness of a concept of the two principal strategies of plant adaptation to hypoxia and anoxia conditions. They are “true” tolerance manifesting at the molecular level under conditions of oxygen deficiency or its absence and “apparent” tolerance, which is realized by avoidance of anaerobiosis due to the long-distance oxygen transport. Therefore, experimental material available now is considered and discussed in this review mainly in the light of these principal notions. Especial attention is paid to the role of stress proteins, which synthesis is induced under hypoxia and anoxia. The results of these experiments confirmed earlier conclusions about the key role of energy (glycolysis and alcoholic fermentation) and carbohydrate (mobilization and utilization of reserved carbohydrates) metabolism in plant adaptation to oxygen deficiency or its absence from the environment. The phenomenon of hypoxic acclimation and its role in plant adaptation to anoxia are also considered. Along with these topics, a further development of pH-stat theory is discussed. A special attention is paid to plant strategy realized by the formation of the net of air-filled spaces (aerenchyma) and long-distance oxygen transport from aerated plant parts to those located in anaerobic environment (apparent tolerance). Among other important aspects, we consider (1) post-anaerobic plant injury by free oxygen radicals; (2) the physiological role of alternative pathways of plant adaptation (nitrate reduction and lipid synthesis); (3) the phenomenon of the adaptation syndrome in plants and possible molecular mechanisms of its realization; and (4) some biotechnological advances in the field of genetic and cell engineering used for the creation of plants more tolerant to anaerobic stress. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present work was to evaluate the effect of thermal and anaerobic treatments on physiological and biochemical parameters in a variety of tomatoes (Lycopersicon esculentum Mill. cv. Colt 45). Treatments applied to mature green tomatoes were: (A) heat treatments by water immersion at 42°C for 30min (HS30′) or for 60min (HS60′); or by air at 38°C for 72h (HS72h); and (B) anaerobic treatments carried out at 20°C under humidified nitrogen atmosphere for 3 days (ANA3d) or 6 days (ANA6d). After treatments, fruits were stored at 2 or 14°C. Parameters evaluated were: colour, total acidity, major organic acids, firmness, and ethanol and acetaldehyde concentration. Anaerobic and long-term heat shock treatments inhibited colour development irrespective of storage temperature. Air heat treatment reduced tritratable acidity by increasing malic acid metabolism. Anaerobic treatments induced ethanol accumulation, which could be reversed during storage for the short treatment (3 days), but not for the longer treatment (6 days). Acetaldehyde concentration was increased by anaerobic treatments, but also by immersion in hot water for 60min, which would produce a “low-aerobic” environment. [Copyright &y& Elsevier]

Abstract: Indoleamine 2,3-dioxygenase (EC 1.13.11.42) is a heme-containing dioxygenase which catalyzes the first and rate-limiting step in the major pathway of l-tryptophan catabolism in mammals. Much attention has recently been focused on the dioxygenase because this metabolic pathway is involved not only in a variety of physiological functions but also in many diseases. In this review, the discovery and unique catalytic properties of dioxygenase are described first, and then the recent findings regarding the dioxygenase-initiated tryptophan metabolism are summarized, with special emphasis on the detrimental role of dioxygenase in side effects of interferon-γ and interleukin-12 (by systemic tryptophan depletion), the escape of malignant tumors from immune surveillance (by immunosuppression caused by tryptophan depletion), several neurodegenerative disorders including Alzheimer’s disease (by an aberrant production of neurotoxin, quinolinic acid), and age-related cataract (due to “Kynurenilation,” a novel post-translational modification of lens proteins with tryptophan-derived UV filters). [Copyright &y& Elsevier]

Peter Hochachka was one of the most creative forces in the field of comparative physiology during the past half-century. His career was truly an exploratory adventure, in both intellectual and geographic senses. His broad comparative studies of metabolism in organisms as diverse as trout, tunas, oysters, squid, turtles, locusts, hummingbirds, seals, and humans revealed the adaptable features of enzymes and metabolic pathways that provide the biochemical bases for diverse lifestyles and environments. In its combined breadth and depth, no other corpus of work better illustrates the principle of "unity in diversity" that marks comparative physiology. Through his publications, his stimulating mentorship, his broad editorial services, and his continuous-and highly infectious-enthusiasm for his field, Peter Hochachka served as one of the most influential leaders in the transformation of comparative physiology. [ABSTRACT FROM AUTHOR]

The superoxide-producing phagocyte NADPH oxidase can be reconstituted in a cell-free system. The activity of NADPH oxidase is dependent on FAD, but the physiological status of FAD in the oxidase is not fully elucidated. To clarify the role of FAD in NADPH oxidase, FAD-free full-length recombinant p47phox, p67phox, p40phox, and Rac were prepared, and the activity was reconstituted with these proteins and purified cytochrome b55s (cyt b558) with different amounts of FAD. A remarkably high activity, over 100 μmol/s/μmol heme, was obtained in the oxidase with purified cyt b558, ternary complex (p47–p67-p40phox), and Rac. From titration with FAD of the activity of NADPH oxidase reconstituted with purified FAD-devoid cyt b558, the dissociation constant Kd of FAD in cyt b558 of reconstituted oxidase was estimated as nearly I nM. We also examined addition of FAD on the assembly process in reconstituted oxidase. The activity was remarkably enhanced when FAD was present during assembly process, and the efficacy of incorporating FAD into the vacant FAD site in purified cyt b55s increased, compared when FAD was added after assembly processes. The absorption spectra of reconstituted oxidase under anaerobiosis showed that incorporation of FAD into cyt b558 recovered electron flow from NADPH to heme. From both Kd values of FAD and the amount of incorporated FAD in cyt b558 of reconstituted oxidase, in combination with spectra, we propose the model in which the Kd values of FAD in cyt b558 is changeable after activation and FAD binding works as a switch to regulate electron transfer in NADPH oxidase. [ABSTRACT FROM AUTHOR]

The Norway lobster, Nephrops norvegicus, is moderately tolerant of sulphide [the lethal time to 50% mortality (LT50) was 22.5 h when exposed to 500 μM sulphide] but, whenever possible, it attempts to avoid the presence of sulphide in its immediate vicinity. Any sulphide entering the animal is oxidized to thiosulphate, which accumulates in the haemolymph and in the tissues. During exposure to low concentrations of sulphide, the rate of oxygen consumption is maintained or even enhanced even though the lobsters become quiescent. The apparent increase in oxygen consumption is probably due to the oxidation of sulphide to thiosulphate. At higher concentrations, oxygen consumption decreases, perhaps because of the inhibitory effect of sulphide on electron transport, and N. norvegicus resorts to anaerobic metabolism as indicated by the accumulation of lactate in the haemolymph and in the tissues. [ABSTRACT FROM AUTHOR]

Isoflavonoids found in legumes, such as soybeans, are converted by intestinal bacteria to metabolites that might have increased or decreased estrogenic activity. Variation in the effects of dietary isoflavonoids among individuals has been attributed to differences in their metabolism by intestinal bacteria. To investigate this variation, the metabolism of the isoflavonoid daidzein by bacteria from ten fecal samples, provided at different times by six individuals on soy-containing diets, was compared. After anaerobic incubation of bacteria with daidzein for 2 weeks, four samples had metabolized daidzein and six samples had not. Three of the positive samples were from individuals whose microflora had not metabolized daidzein in previous samples. Dihydrodaidzein was observed in one sample, dihydrodaidzein and equol in another sample, and equol and O-desmethylangolensin in two other samples. These results corroborate the hypothesis that the microflora of the gastrointestinal tract of an individual influences the particular isoflavone metabolites produced following consumption. [ABSTRACT FROM AUTHOR]

1. During aerobic cation uptake in liver mitochondria, the hydrophobic pH indicator bromothymol blue undergoes a multiphase response: phase 1 (rapid acidification), phase 2 (slow alkalinization), phase 3 (rapid alkalinization) and phase 4 (reacidification). 2. Titrations with ruthenium red and malonate indicate that the various phases depend on the relative rates of cation uptake and proton translocation: at high rates of cation uptake, phase 1 disappears and phases 2 and 3 are transformed in a monotonic process of alkalinization. 3. The comparison of the bromothymol blue response with the arsenazo III, 2',7'-bis(carboxyethyl)5(6)carboxyfluorescein (BCECF) and safranine responses indicates that: (a) phase 2 (slow alkalinization) corresponds to a slow rise of matrix pH and a parallel decline of membrane potential; (b) phase 3 (rapid alkalinization) corresponds to termination of proton translocation and initiation of the processes of cation elf lux and proton reuptake. All the above processes reach completion during phase 4. 4. Although bromothymol blue always behaves as a membrane-bound indicator, the extent to which it reflects the matrix or the cytosolic pH is a function of file membrane-potential-determined asymmetric distribution: in parallel with the lowering of the membrane potential, the dye chromophore is shifted from the cytosolic to the matrix side membrane layer. 5. A model is discussed which describes the behaviour of bromothymol blue as pH indicator recording the changes in membrane layers facing either the matrix or the cytosolic side. The complex response of the dye during cation uptake is due to two independent processes, one of pH change and another of dye intramembrane shift. Computer simulations of the dye response, based on the conversion of a kinetic model into an electrical network and closely reproducing the experimental observations, are reported. [ABSTRACT FROM AUTHOR]

1. The kinetics of acidification and realkalinization of the matrix after addition of nigericin to respiring and non-respiring mitochondria, recorded by intramitochondrial pH indicators such as neutral red and 2',7'bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF), is complementary to that recorded by extramitochondrial pH indicators. The extent of acidification decreases with the logarithm of thc KCl concentration and is inhibited by P1 and ammonium ions.2. Proton translocation during respiration has been compared with proton extraction from matrix bulk water. During oxygen pulses to EOTA-untreated rnitochondria, BCECF records an extraction of protons from matrix bulk water of about 2-3 nmol H+/mg, reduced to 1-2 nmol H+/mg in EGTA-treated mitochondria. Since the amount of proton translocation required to achieve steady state is of the order of 6-7 nmol H+/mg, it appears that 75-90% of the protons are not extracted from matrix bulk water. Only a slight response is recorded by neutral red.3. The effect of permeant cations and of uncouplers on the distribution of proton extraction between membrane and matrix bulk water has been studied in presteady state. During Sr2+ uptake, proton extrusion into cytosolic bulk water, as well as proton extraction from matrix bulk water, corresponds almost to 100% of the protons translocated by the redox proton pumps. In the absence of Sr2+, parallel to the disappearance of the proton extrusion in cytosolic bulk water, the proton extraction from matrix bulk water diminishes to about 20% of the proton translocation.4. The mechanism by which divalent cation uptake and protonophoric uncouplers affect thc distribution of proton extraction between matrix bulk water and membrane domains and the nature of the membrane domains are discussed. [ABSTRACT FROM AUTHOR]

Arthrobacter pyridinolis possesses alternative transport systems for D-fructose: a respiration-coupled transport system whereby D-fructose transport occurs with concomitant oxidation of L-malate, and a phosphoenolpyruvate:D-fructose phosphotransferase system. Studies of D-fructose uptake by whole cells in the presence and absence of cyanide demonstrate that respiration-coupled transport is used almost exclusively during the first half of logarithmic growth, after which it accounts for only 15-20% of D-fructose uptake. Phosphotransferase levels are low during log phase, peak during late log, and then slowly decline. In a mutant of A. pyridinolis which requires δ-aminolevulinic acid for growth, the growth rate, cell cytochrome content, and activity of the respiration-coupled transport system increased with increasing concentrations of δ-aminolevulinic acid up to 50 µg/ml. By contrast, phosphotransferase activity was highest in cells grown on limiting δ-aminolevulinic acid. L-Malate, which stimulates respiration-coupled transport, repressed the phosphotransferase system. The respiratory activity and the ability to release CO2 from internalized D-fructose was consistently low in D-fructose-grown cells. A cyanide-resistant cytochrome, tentatively identified as cytochrome d, appeared in the late exponential phase of growth. Isocitrate lyase activity, required for aerobic growth of this organism, declined markedly during the late exponential phase. Thus the phosphotransferase system is maximally induced, in this obligate aerobe, under conditions of relative anaerobiosis during which metabolism is primarily fermentative. [ABSTRACT FROM AUTHOR]

Mitochondria have been put forward as the saviours of anaerobes when their environment became oxygenated. However, despite oxygenic photosynthesis evolving around 2.7 billion years ago (Ga), followed by the ' Great Oxidation' of the atmosphere ~ 2.4 Ga, the deep oceans remained largely anoxic and either iron-enriched or sulphidic until 580 million years ago, when the eukaryotic radiation was well underway. Atmospheric oxygen probably remained at an intermediate concentration (1-10% of the present level) from ~ 2.4 until ~ 0.8 Ga when a 'lesser oxidation' began. This drastically changes the textbook view of the ecological conditions under which the mitochondrial endosymbiont established itself. It could explain the widespread distribution of anaerobic biochemistry in every eukaryotic supergroup: anaerobic biochemistry is hard-wired into the eukaryotes. [ABSTRACT FROM AUTHOR]

Abstract: We describe the application and evaluation of a widely available commercial jar as an anaerobic container suitable for the growth of a wide variety of anaerobes. A system for generating stable anaerobiosis was developed by combining standard anaerobic environment generators with Click-Clack jars produced by Click-Clack Ltd. (http://www.clickclack.com). This system was simple, reliable, and reduced capital outlay on anaerobic jars by at least an order of magnitude. [Copyright &y& Elsevier]