Saran's Learn Microbiology

IRON UPTAKE BY MICROORGANISMS Almost all microorganisms require iron for use in Cytochromes and many enzymes. Iron uptake is made difficult by the extreme insolubility of ferric iron (Fe 3+ ) and its derivatives, which leaves little free iron available for transport. Many bacteria and fungi have overcome this difficulty by secreting Siderophores. Siderophores are low molecular weight organic molecules that are able to complex with ferric iron and supply it to the cell. These iron-transport molecules are normally either Hydroxamates or Phenolates - catecholates. Ferrichrome is a hydroxamate produced by many fungi; Enterobactin is the Catecholate formed by Escherichia coli . It appears that three siderophore groups complex with iron to form a six-coordinate, octahedral complex. Microorganisms secrete siderophores when iron is scarce in the medium. Once the iron-siderophore complex has reached the cell surface, it binds to a siderophore-receptor protein. Then the iron is either released ...

  Difference between Passive Transport and Active Transport S. No Features Passive Transport Active Transport 1 Transport of nutrients or molecules High concentration of the solute to low concentration of the solute. Low concentration of the solute to high concentration of the solute. 2 ATP requirement ATP is not required ATP is required 3 Movement of molecules Molecules move downwards Uses ATP to pump molecules upwards 4 Types (or) Examples Simple Diffusion, Facilitated Diffusion and Osmosis. Endocytosis, Ectocytosis, Phagocytosis, Pinocytosis and Sodium – potassium pump. 5 Types of particles transported Proteins, Ions, Large cells and Complex sugars. Anything soluble (meaning able to dissolve) in Lipids, Small mon...

  ACTIVE TRANSPORT In Active processes, the cell must use energy (ATP) to move substances from areas of low concentration to areas of high concentration across the Plasma membrane. The substances Actively transported are Ions (Na + , K + , H + , Ca 2 + and CI - ), Amino acids and Simple sugars. Although these substances can also be moved into cells by passive processes, their movement by active processes can go against the concentration gradient, allowing a cell to accumulate needed materials. (i) ATP - BINDING CASSETTE TRANSPORTERS (ABC transporters) ATP - binding cassette transporters (ABC transporters) are important examples of active transport systems. They are observed in Bacteria (most common in Gram negative bacteria) , Archaea and Eukaryotes. 1)     The solute binding protein (Periplasmic binding protein) binds the substrate to be transported and approaches the ABC transporter complex. 2)    The solute binding protein attaches to the trans...

PASSIVE TRANSPORT In Passive processes, substances cross the membrane from an area of high concentration to an area of low concentration (move with the concentration gradient, or difference), without any expenditure of energy (ATP) by the cell. Passive process or Passive transport includes (i) Simple Diffusion, (ii) Facilitated Diffusion and (iii) Osmosis. (i) SIMPLE DIFFUSION Simple diffusion is the net (overall) movement of molecules or ions from an area of high concentration to an area of low concentration. For Example - After a dye pellet is put into a beaker of water, the molecules of dye in the pellet diffuse into the water from an area of high dye concentration to areas of low dye concentration. The movement continues until the molecules or ions are evenly distributed. The point of even distribution is called Equilibrium. Cells rely on simple diffusion to transport certain small molecules, such as Water, Oxygen and Carbon-di-oxide across their cell membranes. (ii) FACILITATE...

 NUTRITIONAL GROUPS OF MICROORGANISMS  1. Classification of Microbial Nutrition based on Carbon sources  a) Autotrophs  Autotrophs are any organisms that are capable of producing their own food. For most, this is achieved by using light energy, water and carbon dioxide (Example – Algae and Cyanobacteria).  All autotrophs use non-living material (inorganic sources) to make their own food.  b) Heterotrophs  Heterotrophs are organisms that obtain their energy (nutrition) from Organic compounds.  2. Classification of Microbial Nutrition based on Energy sources  a) Phototrophs Phototrophs are organisms that use light as their source of energy to produce ATP and carry out various cellular processes. Phototrophs capture light energy and convert it into chemical energy inside their cells. Common examples include Green plants, Algae, Cyanobacteria, Purple non-sulphur bacteria and Heliobacteria.  b) Chemotrophs   Chemotrophs obtain energy...

GROWTH FACTORS  Growth factors are required in small amounts by bacterial cells to fulfill specific roles in biosynthesis.  Growth factors are Organic compounds (Purines, Pyrimidines, Amino acids and Vitamins) that a cell must have for growth but cannot synthesize itself.  Growth factors are organized into three categories. 1) Purines and Pyrimidines - Required for synthesis of Nucleic acids (DNA and RNA) 2) Amino acids - Required for the synthesis of Proteins 3) Vitamins - Needed as Coenzymes and functional groups of certain Enzymes  Some bacteria (e.g. Escherichia coli ) do not require any Growth factors. They can synthesize all essential Purines, Pyrimidines, Amino acids and Vitamins, starting with their Carbon source, as part of their own intermediary metabolism.  Certain other bacteria (e.g. Lactobacillus ) require Purines, Pyrimidines, Vitamins and several Amino acids in order to grow. These compounds must be added in advance to Culture media that are...

  CHEMICAL NUTRIENT REQUIREMENTS ·       Microbial nutrients are the substances that are acquired from the environment and used for growth and metabolism of microorganisms. ·       Microbial cell composition shows that 95 % of cell Dry weight is made up of a few major elements: ü   Carbon ü   Oxygen ü   Hydrogen ü   Nitrogen ü   Sulfur ü   Phosphorous ü   Potassium ü   Calcium ü   Magnesium ü   Iron 1) Macronutrients or Macroelements ·      Macronutrients or Macroelements are required by microorganisms in relatively large amounts. ·        Macronutrients usually help to maintain the Cell structure and Metabolism. ·        Macronutrients exist in the cell as Cations. ·        Four Macronutrients or Macroelements required for Microbial growth are a)...