EnviroRegulationofMicrobialMetabolism-rev

EnviroRegulationofMicrobialMetabolism-rev - Environmental...

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Unformatted text preview: Environmental & Pollution Microbiology Spring 2010 Environmental Regulation of Microbial Metabolism Organized as follows: (I.) Metabolism and Energy Transduction: How bacteria gain fuel (catabolism), and how they make more cells (biosynthesis) and the link between fueling reactions (catabolism) and the generation of cellular energy to keep the bacterial machine working (II.) Enzymes: the catalysts that do all of the work (III.) Transcriptional organization and control: How the metabolic machine is regulated (IV.) Catabolic pathways: Diverse strategies bacteria use to occupy almost every conceivable niche I. Metabolism (1.) Anabolism (= biosynthesis) (A.) metabolism = anabolism + catabolism (B.) anabolism = biosynthetic pathways that lead from the 12 precursor intermediates to cellular building blocks (C.) catabolism = fueling reactions that lead from ingredients of the external medium to the metabolic needs (precursor metabolites , reduced pyridine nucleotides , energy , nitrogen , sulfur ) of the biosynthetic pathways (2.) How do we make sense out of biochemical complexity? (A.) Employ a unit process approach (B.) All of the 75-100 known building blocks, coenzymes, and prosthetic groups are synthesized from only 12 precursor metabolites by reactions that employ energy (high energy phosphate bonds from ATP), reducing power , and sources of nitrogen , sulfur , and single carbon units . (C.) 12 precursor metabolites (D.) Role of the 12 precursors as a pool linking catabolism and anabolism. ATP, reduced pyridine nucleotide, and C1 units are also provided from catabolism to build the precursor pool (3.) intermediates formed during catabolism are used for biosynthesis during anabolism by heterotrophs as well as autotrophs (A.) Consider the resources needed to produce the building blocks to make 1 gram of cells. Treat each pathway as a unit function. Make a list of components (number of enzymes) and metabolic costs (consumption of energy [as high energy phosphate bonds from ATP], reducing power, nitrogen sulfur, and one-carbon units) (B.) Detailed material balance sheet approach to biosynthesis. (4.) Nitrogen assimilation (A.) Precursor metabolites do not contain nitrogen. What is its source? (i.) Entry into cell (ii.) organic forms in soil and sediment habitats are often complexed with polyphenols and tannins (iii.) Always enters biosynthetic pathways in inorganic form, as ammonium ion [NH 4 + ] (B.) Common inorganic sources (C.) Assimilative uptake of nitrate -- Importance of ammonia repression. (D.) Ammonia ultimately is taken into biosynthetic pathways via 2 key enzymatic reactions: glutamine synthetase and glutamate synthase (5.) Nitrogen fixation (A.) only found in bacteria and archaea (B.) mediated by nitrogenase (C.) sequential electron transfer (D.) 6 electron needed to convert nitrogen to ammonia, but 8 electrons are actually transferred (6.) Precursor metabolites do not contain sulfur. What is its source?...
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EnviroRegulationofMicrobialMetabolism-rev - Environmental...

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