Question

3. What are the major elements required for microbial growth, and how are they used by the cell?

Answer 1

Nutrients are required for microbial growth, and play a vital role in proper laboratory cultivation of microorganisms and proper growth in their natural environments. The types of nutrients needed include those that supply the necessary energy, carbon and additional materials. The nutrients used to promote growth are unique to organisms, based on their cellular and metabolism.

Common nutrients found to be important in all living things include carbon, nitrogen, sulphur, phosphorus, potassium, magnesium, calcium, oxygen, iron and other trace elements. Important nutrients are nutrients which an organism completely requires. Macro-and Micro-nutrients are two types of important nutrients.

Mechanism of use by cell :-

Passive Diffusion– Also referred to as simple diffusion, is a mechanism in which molecules from a higher concentration region to a lower concentration area. Through passive diffusion, only very small molecules, such as H2O and CO2 (non-polar) can travel through.

Facillited diffusion- diffusion involving proteins from carriers (permeases). With the concentration gradient the rate of diffusion increases. Major intrinsic proteins (MIPs) facilitate the spread of minor polar molecules. Glycerol is transmitted in bacteria by assisted diffusion.

Osmosis – Movement of solvent molecules through a selectively permeable membrane from a region of higher to lower concentration.

Active Transport– Transport of solute molecules with the input of metabolic energy to higher concentrations. Features: Involves the use of permeases Against concentration gradient Metabolic energy is needed Shows saturation Permeases shows Irreversible movement specificity.

Group translocation –A process in which a molecule is chemically altered when it is introduced into the cell. This is an active form of transport because this uses metabolic energy during molecule uptake. One well-known example is the Phosphoenolpyruvate: sugar phosphotransferase system (PTS) system.

Iron Uptake– Iron for use in cytochromes and many enzymes serves as a very important micronutrient for microbes. The absorption of iron is extremely difficult because of its insoluble properties which leaves little free iron for use. Siderophores are therefore secreted by several bacteria and fungi.