Bacterial Growth Requirements Lecture Notes PDF

Your Midterm (20 points) - Tuesday, November 5th PLEASE ATTEND IN YOUR TIME SLOT Lectures 1 to 4 (T/F, MCQ, Scientific Term)  Lecture # 5: Requirements for bacterial growth Objectives By the end of this lecture, you should be familiar with: Requir...

Your Midterm (20 points) - Tuesday, November 5th PLEASE ATTEND IN YOUR TIME SLOT Lectures 1 to 4 (T/F, MCQ, Scientific Term)  Lecture # 5: Requirements for bacterial growth Objectives By the end of this lecture, you should be familiar with: Requirements for bacterial growth 1. Source of elements. 2. Source of energy. 3. Suitable environmental conditions. (Temperature, pH, Solutes, Oxygen)  1- Source of elements The nutrients required by a microbial cells are : A. Major elements or macronutrients: C, N, O, H, P, S, Na, K, Cl, Mg, Ca, Fe B. Minor (trace) elements or micronutrients: e.g.: Co, Cu, Mn, Mo, Ni, Se, Zn C. Growth factors: (vitamins, amino acids, purines, and pyrimidines) are organic nitrogenous compounds needed by most cells in very small amounts.  Source of carbon Autotrophic Heterotrophic able to utilize carbon dioxide most bacteria require (inorganic carbon) as the carbon as organic sole source of carbon like compounds. plants, they comprise few (sugars, lipids, proteins). number of bacteria.  Source of Nitrogen All bacteria can utilize ammonia (inorganic N2). Most bacteria require one or more organic N2 compounds (as animals) which they cannot synthesize and so must be supplied preformed in food, such compounds are called “growth factors” e.g., vitamin or amino acid. Few bacteria are able to fix atmospheric N2 e.g.: Nitrogen fixing bacteria that grow in symbiosis with roots of legumes.  2- Source of Energy Photosynthetic Chemosynthetic Utilize photons from Utilize energy produced the sun like plants from the oxidation of e.g., Cyanobacteria organic or inorganic and Sulfur bacteria compounds like animals (most bacteria).  3- Suitable Environmental Conditions 1. Effect of temperature. 2. Effect of pH. 3. Effect of water and solutes. 4. The effect of Oxygen.  Effect of Temperature 1) Mesophiles are organisms with an optimum temperature near 37⁰C (the body temperature of warm-blooded animals). 2) Thermophiles are organisms with an optimum temperature between 45⁰C and 70⁰C (moderate thermophiles). Some can grow at 80 degrees or hand higher are now referred to as extreme thermophiles or hyperthermophiles. 3) Psychrophiles are cold-loving organisms defined by their ability to grow at 0 degrees. (has an optimum temperature of 10-15⁰C)  Effect of PH The range of pH over which an organism grows is defined by three points: -Minimum pH, below which the organism cannot grow -Maximum pH, above which the organism cannot grow, -Optimum pH, at which the organism grows best. 1) Acidophiles are microorganisms that grow at an optimum pH well below neutrality (7.0). e.g., Lactobacillus 2) Neutrophiles are microorganisms that grow best at neutral PH 3) Alkaliphiles are those that grow best under alkaline conditions.  Effect of water and solutes Osmophilic : Organisms that require solutions with high solute concentration (sugars or any other solutes). Halophilic : Organisms that require high NaCl concentration e.g. Halobacterium and bacteria that live in the dead sea. Xerophiles: Organisms that live in dry environments.  The Effect of Molecular Oxygen (O2) Obligate Facultative Obligate Aerotolerant Microaero- aerobic anaerobic anaerobic anaerobes philes Effect of Only aerobic Aerobic& Only Only anaerobic Only aerobic growth; anaerobic anaerobic. but growth growth; oxygen on oxygen Growth continues in oxygen growth growth. required Greater growth ceases (stops) presence of required in low in oxygen. in presence of oxygen concentration oxygen Explanation Growth occurs Growth is best Growth Growth occurs Growth occurs in areas where where oxygen occurs only evenly; oxygen only where of growth high conc. Of is present, but where there is has no effect low conc. of pattern oxygen could occurs no oxygen oxygen have diffuse throughout the diffused tube Explanation Bacteria contain enzymes to Bacteria lack Bacteria have only some enzymes neutralize the toxic forms of the enzymes (not all) so the toxic forms of of oxygen's oxygen that neutralize oxygen are partially neutralized effect oxygen , so it becomes harmful How can oxygen be toxic to some bacteria? - Oxygen can accept electrons and form:. superoxide radicle O , hydrogen peroxide (H O ) and hydroxy 2 2 2. radical( OH ). - These radicals are toxic to the cells because they are powerful oxidizing agents and rapidly destroy cellular constituents. - They are detoxified by enzymes (superoxide dismutase, catalase and peroxidase). - If the enzymes are not present, the cells cannot tolerate oxygen (Obligate Anaerobic do not have them at all). (Microaerophilic and Aerotolerant have only one type)  Summary Requirements for bacterial growth 1. Source of elements.√ 2. Source of energy. √ 3. Suitable environmental conditions. √ (Temperature, pH, Solutes, Oxygen)  Your Midterm (20 points) - Tuesday, November 5th PLEASE ATTEND IN YOUR TIME SLOT Lectures 1 to 4 (T/F, MCQ, Scientific Term)