BIOLOGY 2A03 Lecture Notes - Lecture 15: Auxotrophy, Ammonium Chloride, Isoleucine
12 Dec 2018
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Outline: nutritional requirements of microorganisms, factors affecting microbial growth, growing microorganisms in the laboratory, measuring microbial population growth, eliminating microbes and preventing their growth. What is the composition of microbes: macromolecules: dry weight of the cell, polypeptides 50-55, nucleic acids (dna, rna) 2-5, lipids 10, polysaccharides 6-7, microorganisms must obtain these elements from their environment. Source of energy: chemotrophs, energy from oxidation of reduced organic or inorganic compounds, phototrophs, energy from light. Electron sources: organotrophs: electron from organic molecules (glucose, lithotrophs (rock-eaters): electrons from inorganic sources (h2 gas, nh4, h2s) Source of carbon: autotrophs assimilate carbon from inorganic sources, heterotrophs assimilate carbon in pre-existing organic form. Ammonia assimilation: two different systems incorporate ammonia into amino acids, gs-gogat works best at low ammonium concentrations, gdh (glutamate dehydrogenase) works best at high ammonium concentrations. Biosynthesis of cellular components: amino acid synthesis, main pathway gives the initial carbon skeleton of amino acids, glutamine/glutamate donate amino groups for other amino acids.
