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BACTERIAL NUTRITION, The nutrition is, "the series of, processes by which, assimilates food for growth and, "., , MICROB, , TOLOGY, , organism, repair, Every, must, find, organism, in its, environment all of the substances, for, required, energy generation and, cellular biosynthesis. Substances taken, a cell, an, , from its environment and, by, anabolic reactions is called as nutrients., Microorganisms very greatly in their nutritional requirements. Thousands, of different media have been, developed for cultivation of bacteria. Culture, media are designed to, provide all essential nutrients in aqueous phase for, bacterial growth., , their, , in, , use, , catabolic, , or, , NUTRITIONAL REQUIREMENTS, The chemical, , composition, , of cells is more or less constant, throughout the living world. The chemical composition of an organism, gives rough idea of nutritional requirements. In other words an organism, requires those elements which form part of cell material. The general, nutritional requirements are given below., WATER, , In quantitative terms, water is a major essential nutrient. It accounts, , for about 80 to 90 % of the total weight of the cell. All nutrients must be in an, aqueous solution before they can enter the cell. The biochemical reactions, that occur in cells require an aqueous environment. Water is also a chemical, reactant, being required for many hydrolytic reactions that occur in a cell., MACROELEMENTS, , The major elemental requirements of a bacterium such as E. coli, consists of carbon, oxygen, nitrogen, hydrogen, phosphorus, sulfur,, potassium, magnesIum, calcium and iron. These elements are required in, , relatively high concentration (0.1mM) and are called macronutrientsor, macroelements (table 6.1). These elements occur in water, inorganic ions, , small molecules, and macromolecules. Carbohydrates, proteins, lipids and, nucleic acids contain first six (CONHPS) elements. Other four elements are, cations and play a number of roles., MICROELEMENTS, , All, , microorganisms, , require, , certain, , elements, , in, , very, , low, , concentration (1000 to 100000 mM), such elements are called trace, elements or micronutrients. The micronutrient requirements of most, , microorganisms, molybdenum., , consists of manganese, zinc, cobalt, copper, nicke! and
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Micsbal nul ulion, , macroelements, their, Table 6.1: The, MACROE, , DRY, , LEMENT, , WT, , sources, , PHYSIOLOGICAL FUNCTION, , 50 %, , Main, , compounds, Organic compounds., H,0. CO, and O, , 20 %, , 14 %, , Nitrogen, , N2. NH3. NO, and, organic compounds, , H2. HO and organic, 8%, , Hydrogen, , and in aerobic respiration, , water, , final e-accepter, acid. purines., Constituent of amino, pyrimidines and coenzymes, , cell, of celi material and, , Constituent, , Constituen!, , Phosphorus, , phospholipids., , (PO4), , teichoic acids, , 1, , Sulfur, , %, , S. SO4. H2S, , organic, , sulfur compounds, , acids., , nucleic, , of, , Inorganic phosphate, , and, , cell, , material., , of cell, , water, , compounds, , 3 %, , of cell material, , constituent, , Constituent, , Oxygen, , bacteria, , SOURCE, , CO or organic, , Carbon, , and functions in, , cysteine., , of, , Constituent, , and, , ATP, , LPS., , B, , glutathione., , methionine, , vitamins and several coenzymes, , cofactor, Main cellular cation and, , 1%, , Potassium, , Salts of potassium, , for, , enzymes, , some, , cytochrome, , such,, , oxidase and, , as, , pyruvate., , kinase, , of chlorophyll and, , constituent, , Magnesium, , 0.5%, , Salts of magnesium., , such, cofactor for certain enzymea, as kinases and ATPase, , Important, Calcium, , 0.5 %, , Salts of calcium, , cofactor, as, , Salts of iron, , 0.2 %, , cation,, , cellular, , for, , lipase and, , Constituent, , Iron, , cation., , cellular, , Important, , and, , certain enzymes such, lecithinase, , of cytochrome, , and, , and, ceTtain nonheme iron-proteins, cofactor for certain enzymes such, , as catalase and peroxidases, , It is, , media as, micronutrients to culture, not necessary to add, , present as contaminanty, , t . ' e r or, , media components., , They, element and vice, element may be another's required, trace, One organism's, in microorganisms are given, , nutrients., , are, , functions, The micronutrients and their, in table 6.2, , versa., , CARBON,, , ENERGY, , AND, , ELECTRON, , production, some form for energy, in, All organisms require, source ot, as sole, CO,, require, for cell synthesis. Some organisms, self; t r e * e, autos, carbon, , and, , abon, Such organisms, , =, , are, , termed autotrophs (Gr., , nourisning). Other organisms, , require organic carbe, , =, , ca, , as
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80, , Miorobial nuulnilion, , sole source ofcarbon, such organisms are termed heterotrophs (Gr. hetero=, , difterent)., Table .2: The microelenments and theirfunctions in microbial cells, MICROELE, MENT, , Manganese, , FUNCTION, , Cofactor, , for. phosphoenol, , cartoxykinase,, , pyruvate, , superoxide dismutase, , Zinc, , Cofactor for alcohol dehydrogenase, aldolase, RNA and, , Cobalt, , DNA polymerase, Constituent of vitamin Bi2, Cofactor for cytochrome oxidase and oxygenases, , Copper, Nickel, , Cofactor for urease, , Molybdenum, , Cofactor for nitrogenase, , All organisms require a utilizable source of energy for growth and, , activity. Some organisms use chemical compounds (organic or inorganic), as source of energy and are called chemotrophs. Others use light as source, , ofenergy and are called phototrophs., All organisms require a source of electrons for metabolism. Some, are, use reduced inorganic substances as source of electrons and, , organisms, , called lithotrophs (i.., rock-eaters). Others use organic compounds as, , source of electrons and are called organotrophs. The table 6.3 gives groups, oforganisms and their source of carbon,electron and energy., , Table 6.3: Groups of organisms and their source ofcarbon ,clectron and energy, GROUP, , SOURCE, , CO2, , Autotrophs, , Organic compounds, , Heterotrophs, , Light, , Phototrophs, , Organic or inorganic compounds, , Chemotrophs, , Reduced inorganic compounds, , Lithotropis, , Organic compounds, , Organotropl1s, , Carbon source, , Energy source, , Electron source, , =, , oXYGENAND HYDROGEN, Oxygen and hydrogen are constituents of celi material and cell, water. The compounds serving as carbon source also provide oxvgen and, hydrogen atoms. These elements as water ere used as solutioa and n, hydrolysis, ionization, osmosis, etc. Molecular O, is used as final electron
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81, , Micabial nudrilion, , accepter, , in, , respiration. f/ydrogenomonas species, , aerobie, , use, , molecular, , H,, , as sourceofenergy., AND, NITROGEN, U L F U R, , PHIISPHORU1S, , nitrogen,, serving as carbon source also provide, constituent of amino acid, purines,, sulfur and phosphorus. Nitrogen is a, nitrogen in some form., pyrimidines and coenzymes. All organisms require, and Rhizobium species require, Some bacteria such as Azolobacter, compounds such as, molecular nitrogen. Others require inorganic nitrogen, The compounds, , nitrates, nitrites, , or, , compounds such, , as, , Still others require organic nitrogen, nitrate for, amino acids. Same organisms require, ammonia., , anaerobic respiration., methionine, glutathione, B, Sulfur is constituent of cysteine,, several coenzymes. All organisms require, vitamins(biotin and thiamin) and, as Thiobacillus species require, sulfur in some form. Some bacteria such, sulfur compounds such as salts of, , require inorganic, such as cysteine,, sulfates. Still others require organic sulfur compounds, sulphate for, methionine, glutathione, B vitamins. Some organisms require, elemental sulfur. Others, , anaerobic respiration., , LPS,, Phosphorous is constituent of nucleic acids, phospholipids,, in some form of, ATP and teichoic acids. All organisms require phosphorus, include phosphate as buffering, phosphate. Synthetic media often, media e.g., nutrient, substances (K,HPO, and KH,PO,). M senmi synthetic, in the constituents of, broth, phosphate arise from nucleid acids present, media (meat extract),, GROWTH FACTÓRS, , Some microorganisms require small amounts of certain organic, compounds for growth because they are essential substances that the, , organism is unable to synthesize from available nutrients. Such organic, , compounds, , are, , called, , growth, , factors., , Following compounds, , serve as, , growth factors (table 6.4)., , 1.Purinesand pyrimidines, They serve as precursors for synthesis of nucleic acids., 2. Amino acids, They serve as precursors for the synthesis of proteins., , 3.Vitamins, They serve as coenzymes and functional groups of certain, , enzymes., An organism that requires one or more growth factors is called, , auxotropn, and the organism that requires no growth factors is called, prototroph (or organism with same nutritional reirements as s, , ancestors).
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83, , Micrebial nuleiion, , sulfur, exceptions. For example, Hydrogenonmonas species; the purple non, bacteria such as Rhodospirillum, Rhodomicrobium and Rhodopseudomonas, green nonsulfur bacteria and Beggiatoa species are capable of growWIng, , either autotrophically or heterotrophically. Çertain common intestinal, , bacilli can grow well in a simple and compktely inorganic medium with, sodium citrate as carbon source. In addition to organic carbon compounds,, , most heterotrophs require traces of C0, To overcome these difficulties microorganisms are classified based, , on carbon and energy source. This is most useful, relatively simple, nutritional classif+cation (fig. 6.1)., are classified as, Based on nature of energy source microorganisms, "phototrophs" and "chemotrophs"., PHOTOTROPHS, , The, , organisms which,, , utilize radient energy, , (light), , as a source, , of, , energy are called phototroplhs., CHEMOTROPHS, , The, , organisms which, obtain, , energy, , by oxidation, , compounds are called chemotrophs., Based on carbon and energy source microorganisms, , of chemical, are, , classified, , into four groups:, T. Photoautotrophs, , 2. Chemoautotrophs, 3. Photoheterotrophs, 4. Chemoheterotroph, , 1.PHOTOAUTOTROPHS, as, that utilize radient energy, the, organisms, Photoautotrophs, source., and CO, as principal carbon, source ofenergy, sulfur bacteria,, include, are, , purple, organisms, Thiosarcina, species); green, Thiocystis, and, Thiospirillum,, (Chromatium,, cyanobacteria (Oscillatoria,, bacteria (Chlorobium species);, Photoautotrophic, , sulfur, , algae and plants., donor in the, water as electron, use, cyanobacteria, Algae, plants and, , Anabaena species);, , photosynthetic reduction of C0, , (CHO), , Light, , +H.O O., , CO.+2H,O, Ihe purple, , sulfur and, , donor in the photosynthetic, , bacteria use, green sulfur, , reduction, Light, , CO,2HS, , of CO,, (CHO), , HS, , as, , electron
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Mcobial nutilion, , 85, , PHOTOHETEROTROPHS, Photoheterotrophs are the organisms that utilize radiant energy as, source of energy and organic compounds as princinal carbon source., , Photoheterotrophic organisms include purple nonsulfur bacteria,, (Rhodospirillum, Rhodomicrobium and Rhodopseudomonas species) and, green nonsulfur bacteria (Chloroflexus species)., , These bacteria use organic compounds such as fatty acids, organic, , acid. primary and secondary alcohols, carbohydrates and even aromatic, compounds as electron donor. For example, Rhodospirillum rubrun use, , succinate as electron donor., CO, , + Succinate, , Laght, , (CH,O) + H,O + Fumarate, , The purple nonsulfur bacteria and green nonsulfur bacteria can also, grow photoautotrophically using H,S as an electron donor in photosynthetic, , CO,reduction., Certain photoheterotrophs can grow as chemohetrerotrophs, for, , example, Rhodospirillum rubrum under anaerobic condition use light as, energy source and grows as photoheterotroph; whereas, under aerobic, , condition it grows in dark as chemoheterotroph. Such organisms are called, , mixotrophs., CHEMOHETEROTROPHs, Chemoheterotrophs are the organisms that obtain energy by, Oxidation of organic compounds and use organic compounds as principal, carbon source., , Chemoheterotrophs include animals, many bacteria and most, fungi. The source of carobon (e.g. glucose) is also functions as source of, energy. Many chemoheterotrophs also require small amount of C0, in the, intracellular synthesis., Certain bacteria can grow either as chemoheterotrophs or, chemohetrerotrophs, for example, pseudomonas pseudoflava can use, either organic compounds glucose or the inorganic compound H, as its, source of electrons., , CH,O, + 6H,0, , 6CO, +24H +24e, 2H +2e, , Microorganisms are nutritionally versatile. This versatility makes, nutritional categories arbitrary to some extent., , For example, many
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Microbal nulilion, , 86, , photoautotrophic organisms can grow in dark as chemoautotrophs. Certain, photoautotrophs and chemoautotrophs can grow as chemoheterotroplhs. To, indicate presence or absence of, nutritional versatility the terms obligate and, facultative are often used. Thus, an obligate, photoautotroph solely use light, as, energy source and CO, as principal carbon source whereas, facultative, photoautotrophs is not., A summary of nutritional, categories of microorganisms is given in, the table 6.6., , Table 6.6: Nutritional categories of, NUTRIT1O, , CARBON, , ENERGY, , NAL TYPE, , SOURCE, , SOURCE, , CO, , autotrophs, , heterotrophs, , EXAMPLES, , Purple, , Photo, Photo, , microorganisns, , Light, , sulfur, , sulfur, , bacteria,, , green, , bacteria,, , algae., , cyanobacteria and plants, , Organic, compounds, , Light, , CO2, , Inorganic, compounds, , Chemo-, , autotrophs, Chemo-, , Organic, , Organic, , heterotrophs, , Compounds, , compounds, , =, , nonsulfur bacteria and, green nonsulfur bacteria,, , Purple, , Nitrobucter, Nitrosomonas, , species, , species, , and, , Thiobacillus species, Most bacteria, fungi and animals
