Microbial Nutrition

NUTRITIONAL REQUIREMENT • To obtain energy and construct new cellular components, organisms must have a supply of raw materials or nutrients. • Nutrients are substances used in biosynthesis and energy production and therefore are required for microbial growth

The Common Nutrient Requirements • Analysis of microbial cell composition shows that over 95% • Macro elements Or Macronutrients -carbon, oxygen, hydrogen, nitrogen, sulphur, phosphorus, potassium, calcium, magnesium, and iron-required in relatively large amounts. • The first six (C, O, H, N, S, and P) are components of carbohydrates, lipids, proteins, and nucleic acids

• potassium (K) is required for activity by a number of enzymes, including some of those involved in protein synthesis. • Calcium (Ca2), among other functions, contributes to the heat resistance of bacterial endospores. • Magnesium (Mg2) serves as a cofactor for many enzymes, complexes with ATP, and stabilizes ribosomes and cell membranes. • Iron (Fe2+ and Fe3+) is a part of cytochromes and a cofactor for enzymes and electron-carrying proteins • Molybdenum (Mo2) is required for nitrogen fixation,

• The micronutrients,manganese, zinc, cobalt, molybdenum, nickel, and copper are needed by most cells. • Micronutrients are normally a part of enzymes and cofactors, and they aid in the catalysis of reactions and maintenance of protein structure. • zinc (Zn2+) is present at the active site of some enzyme • Manganese(Mn2+) aids many enzymes catalyzing the transfer of phosphate groups

REQUIREMENTS FOR CARBON,HYDROGEN,AND OXYGEN

• Carbon --skeleton or backbone of all organic molecules, and molecules serving as carbon sources normally also contribute both oxygen and hydrogen atoms • only autotrophs can use CO2 as their sole or principal source of carbon • carry out photosynthesis and use light as their energy source.

• The reduction of CO2 is a very energy-expensive process. • But must rely on the presence of more reduced, complex molecules such as glucose for a supply of carbon • Organisms-reduced, preformed organic molecules as carbon sources are heterotrophs • No Naturally occurring organic molecule that cannot be used by some microorganism. • For ex- Actinomycetes will degrade amyl alcohol, paraffin, and even

• Cultures of methylotrophic bacteria metabolize methane, methanol, carbon monoxide, formic acid. • Leptospira use only long-chain fatty acids as their major source of carbon and energy.

Nutritional Types of Microorganisms • There are only two sources of energy available to organisms: (1) light energy,(Phototrophs) (2) the energy derived from oxidizing organic or inorganic molecules(chemotrophs) • Lithotrophs (i.e., “rock-eaters”) use reduced inorganic substances as their electron source, whereas organotrophs extract electrons

• Photolithotrophic autotrophs (often called photoautotroph or photolithoautotrophs) use light energy and have CO2 as their carbon source. • Eukaryotic algae and cyanobacteria employ water as the electron donor and release oxygen. • The (chemolithoautotrophs), oxidizes reduced inorganic compounds such as iron, nitrogen, or sulfur molecules to derive both energy and electrons for biosynthesis. Carbon dioxide is the carbon source. • A few chemolithotrophs can derive their carbon from organic sources and thus are heterotrophic. Chemolithotrophs contribute greatly to the chemical transformations of elements (e.g., the conversion of ammonia to nitrate or sulfur to sulfate) that continually occur in the ecosystem.

NITROGEN • All organisms need N to synthesise enzymes, other proteins & nucleic acid • Some organisms obtain N from inorganic sources; a few obtain energy from metabolising inorganic N containing substances • Many micro-organisms reduce nitrate (NO3 -) to amino groups (NH2) and use the amino groups to make amino acids. • Many micro-organisms can utilise ammonia as the sole N source • Nitrogen fixing bacteria can take up nitrogen directly from the atmosphere( Rhizobium spp)

PHOSPHOROUS & SULFUR • present in nucleic acids, phospholipids, nucleotides like ATP, several cofactors, some proteins, and other cell components. • Sulfur is needed for the synthesis of substances like the amino acids cysteine and methionine, some carbohydrates, biotin, and thiamine.

OTHER MACRONUTRIENTS • Potassium – required for enzymes especially those involved in protein synthesis. • Magnesium – stabilises ribosome, cell membranes & nucleic acids; also required for the activity of many enzymes. • Calcium – not essential for the growth of many organisms but helps stabilise the bacterial cell wall & plays a key role in the heat

Micronutrients (trace elements) • Critical to cell function even if only required in small amounts. • Micronutrients are metals – structural role in many enzymes • Examples include cobalt, manganese, molybdenum nickel selenium zinc.

Growth factors • Organic compounds required because they are essential cell components or precursors of such components and cannot be synthesized by the organism are called growth factors. • (1) Aminoacids, • (2) Purines And Pyrimidines, • (3) Vitamins