Studies on the physiology and ecology of black-pigmented Gram-negative anaerobes which may be important in disease development (original) (raw)
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Metabolism and energy generation in homoacetogenic clostridia
FEMS Microbiology Letters, 1990
Clostridium thermoautotrophicum and C. thermoaceticum contain an anaerobic electron transport chain. It involves hydrogen and carbon monoxide as electron donors and, presumably, methylenetetrahydrofolate as physiological electron acceptor. Cytochrome bss4, cytochrome bssg, menaquinone, a flavoprotein, ferredoxin and rubredoxin are parts of the electron transport chain. The electron transport results in the generation of a proton motive force which drives the synthesis of ATP or the uptake of amino acids.
FEMS Microbiology Reviews, 1995
The metabolism of Clostridium acetobutylicum was manipulated, at neutral pH and in chemostat culture, by the addition of Neutral red, a molecule that can replace ferredoxin in the oxido-reduction reactions catalysed by the enzymes involved in the distribution of the electron flow. Cultures grown on glucose alone produced mainly acids while cultures grown on glucose plus Neutral red produced mainly alcohols and butyrate and low levels of hydrogen. We demonstrated that just after addition of Neutral red to an acidogenic culture, the simultaneous utilizations of ferredoxin and dye deviate electron flow from hydrogen to NADH production initially by the enzymatic regulation of in vivo hydrogenase and ferredoxin NAD reductase activities. The higher NAD(P)H pool generated might, thereafter, be the signal for the setting up of a new metabolism. In the resulting steady-state, the NAD(P)H 'pressure' is maintained by high ferredoxin NAD and NADP reductases level associated to a low NADH ferredoxin reductase level. The regeneration of NAD is mainly achieved via the induced or increased NADH-dependent aldehyde and alcohol dehydrogenase activities.
MCB 303) MICROBIAL PHYSIOLOGY AND METABOLISM {Dr. Chy. Ezemba
Since we are familiar with the structure of prokaryotic cells, we can discuss the activities that enable these microbes to thrive. The life-support processes of even the most structurally simple organism involve a large number of complex biochemical reactions. Most, although not all, of the biochemical processes of bacteria also occur in eukaryotic microbes and in the cells of multicellular organisms, including humans. However, the reactions that are unique to bacteria are fascinating because they allow microorganisms to do things we cannot do. For example, some bacteria can live on cellulose, whereas others can live on petroleum. Through their metabolism, bacteria recycle elements after other organisms have used them. Still other bacteria can live on diets of inorganic substances such as carbon dioxide, iron, sulfur, hydrogen gas, and ammonia. Microbial metabolism allows some microorganisms to grow in or on the human body as shown in dental plaque. 1.0 Concept: Physiology is the study of the processes which go no in living organisms. While on the other hand the term Metabolism to refer to the sum of all chemical reactions within the cells of a living organism. Because chemical reactions and the processes involve building up (Anabolism) while breaking down of nutrients within a cell is termed (Catabolism). Metabolism can be viewed as an energy-balancing act and this balanced flow of chemicals and energy maintains the life of a cell. These chemical reactions provide energy and create substances that sustain life. So Pathways can be categorized into two general types— catabolic and anabolic.
Journal of Bacteriology, 1994
Glycerol-glucose-fed (molar ratio of 2) chemostat cultures of Clostridium acetobutylicum were glucose limited but glycerol sufficient and had a high intracellular NADH/NAD ratio (I. Vasconcelos, L. Girbal, and P. Soucaille, J. Bacteriol. 176:1443-1450, 1994). We report here that the glyceraldehyde-3-phosphate dehydrogenase, one of the key enzymes of the glycolytic pathway, is inhibited by high NADH/NAD ratios. Partial substitution of glucose by pyruvate while maintaining glycerol concentration at a constant level allowed a higher consumption of glycerol in steady-state continuous cultures. However, glycerol-sufficient cultures had a constant flux through the glyceraldehyde-3-phosphate dehydrogenase and a constant NADH/NAD ratio. A high substitution of glucose by pyruvate [P/(G+P) value of 0.67 g/g] provided a carbon-limited culture with butanol and butyrate as the major end products. In this alcohologenic culture, the induction of the NADH-dependent butyraldehyde and the ferredoxin-...
Applied Microbiology and Biotechnology, 2002
The anaerobic metabolism of Enterobacter aerogenes was studied in batch culture at increasing initial glucose levels (9.0<S o <72 g l-1). The ultimate concentrations of fermentation products were utilized to check a metabolic flux analysis based on simple carbon mass and energy balances that promise to be suitable for the study of different fermentation processes, either under aerobic or anaerobic conditions. The stoichiometric coefficients of products collected at increasing starting glucose concentrations under anaerobic conditions suggest: (a) little influence of starting glucose level on the formation of the main fermentation products (2,3-butanediol and ethanol); (b) possible inhibition of 2,3-butanediol and lactate formations by increased ethanol concentration; (c) consequent increase in carbon flux through the remaining metabolic pathways with increased molar productions of succinate, acetate and hydrogen; (d) relative constancy of the molar production of ATP and CO 2 .
1999
Overall metabolic behaviour of a gram positive, anaerobic, spore forming, thermophilic bacteria C. therrn o eel/urn DSM 2360 during different stages of cellular differentiation and development from vegetative cells to spores has been studied. Changes were observed in the cellular contents of reducing sugars, inorganic, TCA-soluble and TCA-insoluble phosphorus, total , phospho- and glycolipids, proteins, DNA and RNA at different stages of devel opment and differentiation . Inhibitor studies on macromolecules revealed interesting differences in protein, DNA and RNA at different stages. The growth and development of all higher animals and plants involves the growth and division of their component cells and may be accompanied by progressive cellular differentiation , as the initial cell line develops into the various tissues that comprise the whole organism. Nevertheless, sin ce the growth and division of single cell is a common denominator, it is appropriate to include studies of cel...
Influence of substrate carbon on the metabolism of Clostridium thermohydrosulfuricum
FEMS Microbiology Letters, 1989
The concentration of carbon sources has a significant influence on the growth, carbohydrate uptake and metabolite distribution in Clostridium thermohydrosulfuricum. The growing concentrations of glucose or starch increase the production of ethanol and lactate, the intracellular fructose-1,6-diphosphate (FDP) and the specific activity of lactate dehydrogenase (LDH), but decrease the ethanol/lactate ratio.
Applied and Environmental Microbiology, 2004
Acetate threshold concentrations were determined under chlororespiring and Fe(III)-reducing conditions for Anaeromyxobacter dehalogenans strain 2CP-C. The acetate threshold concentrations measured were 69 ± 4, 19 ± 8, and <1 nM for chlororespiration, amorphous Fe(III) reduction, and Fe(III) citrate reduction, respectively. Residual Δ G values of −75.4 kJ/mol of electrons for chlororespiration and −41.5 kJ/mol of electrons for amorphous Fe(III) reduction were calculated at the acetate threshold concentration. By comparing threshold concentrations for different metabolisms in a single organism, this study provides insight into the metabolic use of energy under different growth conditions.