Microbial cells are structurally complex. Organisms need nutrients & a source of energy, also known as ‘MICROBIAL NUTRITION’ to carry out numerous functions. NUTRIENTS are substances used in biosynthesis of bacteria. So that microbial nutrition is directly proportional to the microbial growth. Therefore Growth is impossible without nutrition.

THESE NUTRIENTS ARE CATEGORISED AS:- 1. MACRO-NUTRIENTS OR MACRO-ELEMENTS 2. OTHER MACRO-NUTRIENTS 3. MICRO-NUTIENTS OR TRACE EEMENTS 4. ORGANIC GROWTH FACTORS 5. LIGHT 6. WATER 1. THE MACRO-NUTRIENTS OR MACRO-ELEMENTS:- o carbon, hydrogen, oxygen, nitrogen, phosphorus and sulphur. o They are essential elements because they required in large amounts. o They contain 95% of dry weight of the microbial cells.

MACRO- NUTRIENTS FUNCTIONS CARBONNeeded for the skeletons & backbones of all the organisms, molecules from which organisms are built. OXYGEN & HYDROGEN Available from water added to culture media for growth and found in organic molecules NITROGENNature component of protein & nucleic acid. Sources are organic & inorganic nitrgeneous compound. PHOSPHORU S needed as a part of nucleic acid, co-enzyme NAD & FLAVIN & ATP. SULPHURIt forms apart from the structure of several co-enzyme. They all are components of carbohydrates, lipids, proteins, nucleic acids.

NUTRIENTSFUNCTIONS POTASSIUMHelps in activity by a no. of enzymes that is including some involved in protein synthesis. CALCIUMContributes to the heat resistance of bacterial endo-spores. MAGNESIUMServes as a co-factor for many enzymes, complexes with ATP, & stablize ribo-somes & cell membrane. IRONIt is part of cyto-chromes & a co-factor for enzymes & electron carrying protein.

Micro-nutrients are needed in small amounts. These nutrients are:- Magnese, zinc, cobalt, nickel & copper. Cells require such small amounts that contaminates from water, regular media components often are adequate for the growth. They are normally a part of enzymes & co-factors. They aid in the catalysis of reactions & maintainence of protein structure.

Organic compounds that are essential cell compounds or precursors of such components are called ‘Growth factors’. The major classes of growth factors are:- 1. AMINO ACIDS:- Needed for protein synthesis. 2. PURINE & PYRIMIDINE:- Helps in nucleic acid synthesis.

VITAMINS:- They are small organic molecules that usually make up all or part of enzyme, co-factor & are needed in only very small amounts to sustain growth, also known as ‘bacterial vitamins’. Some bacteria’s synthesis their own vitamins & while other need to take them from outside. This varies from bacteria to bacteria.

Micro-organisms need light ( nm) for the photosynthesis of vitamins & minerals & for pigments. 6. WATER Water is important, because all nutrients should be in solution form before they can enter in organisms. ENVIRONMENT FACTORS:- There are some environment factors which also influenced to microbial growth. These factors are like:- Air, Temperature, pH, Radiations, Osmotic pressure etc.

INTRODUCTION:- A Nutrient material prepared for the growth of micro- organisms in a lab. Is called a ‘culture medium’. Some bacteria can grow well on just about any culture medium. Others require special media & still others cannot grow on any non-living medium yet developed. When microbes are introduces into a culture medium to initiate growth, they are called an ‘inoculum’. The microbes that grow & multiply in or on a culture medium, are referred to as ‘culture’.

CULTURE MEDIA can be constructed completely from chemically defined components (defined media or synthetic media) or constituents like peptones & yeast extract(complex media). Culture media can be solidifying by the addition of agar, a complex polysaccharide from red algae.

Culture media is needed to grow the organisms & the constituents are:- 1. Water:- i.e. source of hydrogen & oxygen. 2. Electrolytes:- i.e. sodium chloride. 3. Peptone:- it is a complex mixture of partially digest protein. 4. Meat extract 5. Blood or serum 6. Agar:- which is used in 2-3% constituent. A small amount of protein & many inorganic compounds.

S. NO BASED ON PHYSICAL NATURE BASED ON PRESENCE ON OXYGEN & NITROGEN BASED ON CHEMICAL COMPOSITION BASED ON FUNCTIONAL TYPE & SPECIAL MEDIA 1LIQUID MEDIA e.g. nutrient broth AEROBICSIMPLE MEDIA:- W/c is routinely applied on the lab., To see motile bac., E.g. soft agar ENRICHED:- when basal medium add with other medium, like blood serum, agar. E.g. for growing streptococus 2SEMI-SOLID MEDIA e.g. soft agar ANAEROBICCOMPLEX MEDIA :- contain some ingredients of unknown composition. Needed for growth of bacteria. E.g. nutrient broth etc. ENRICHMENT: - it has stimulating effect of a bac. To grow or inhibit its compe-tatives. TYPES OF MEDIA

3)SOLID MEDIA e.g. nutrient agar SYNTHETIC MEDIA:- Prepared from pure chemicals, & used to study metabolic requirement. SELECTIVE:- help in the isolation of a particular species e.g. DCA agar colony gives deoxycholate 4)DIFFRENTIAL:-it diffrentiate b/w 2 bac’s. e.g. Mackonkey’s agar diffrentiate b/w lactose & non-lactose fermenting. 5)INDICATORS:- It s colour change when a specific bac. Grows on it. E.g salmoneela. 6)TRANSPORT:- For delicate org. for transferring them. 7)SUGAR:- Helps in identification of bac..e.g. glucose et. Are needed in fermentation testhelps in identifying.