Lec 14 Bacterial Physiology Growth and Nutrition, 2007 PDF

Bacterial Physiology (Growth and Nutrition) SCI08 2007 Medical Microbiology and Parasitology Theeraya Simawaranon, Ph.D., AFHEA. School of Pathology, Institute of Medicine, Suranaree University of Technology  Requirements for bacterial growth Carbon and N...

Bacterial Physiology (Growth and Nutrition) SCI08 2007 Medical Microbiology and Parasitology Theeraya Simawaranon, Ph.D., AFHEA. School of Pathology, Institute of Medicine, Suranaree University of Technology  Requirements for bacterial growth Carbon and Nitrogen Source Energy Source Heterotrophs: carbon from Chemoorganotrophs: from the breakdown organic compounds such as of organic molecules by fermentation or respiration. Chemolithotrophs oxidize inorganic ions such as polysaccharides, carbohydrates, nitrate or iron to obtain energy to fix carbon amino acids, peptides, and dioxide. proteins. Photoautotrophs contain photosynthetic pigments such as chlorophyll for photosynthesis. Autotrophs: from fixing carbon Photoheterotrophs: from photosynthesis, but their dioxide. carbon needs come from growth on organic molecules such as succinate or glutamate  Major nutritional requirements for bacterial growth Most bacteria of medical importance require carbon, nitrogen, water, inorganic salts and a source of energy for growth.  Bacterial Metabolism Pathogenic bacteria exhibit heterotrophic metabolism. All bacteria obtain energy by oxidizing preformed organic molecules (carbohydrates, lipids and proteins) from their environment. Metabolism of these molecules yields ATP as an energy source. - Aerobic, the final electron acceptor is oxygen. - Anaerobic, the final acceptor may be an organic or inorganic molecule.  Anabolic processes (synthesis of cellular constituents requiring energy). Itwescus= now Catabolic processes (breakdown of cellular constituents with concomitant release of waste products and energy-rich compounds). Elements and Water Nucleic Acids Lipids, Sugars, Carbohydrates, Amino acid  Metabolism 3 stages Intermediary metabolism: the utilisation of a carbon source, e.g. glucose, to provide energy and small molecules such as pyruvate. N Biosynthetic pathways: to build these small molecules with nitrogen, S sulphur and other minerals into amino acids, purines, pyrimidines, polysaccharides and lipids. Genetic instructions: to build these into macromolecules and bacterial organelles ready for cell division.  EMP Intermediary metabolism Embden-Meyerhof-Parnas glycolytic pathway (EMP) - which converts glucose to pyruvate with the formation of ATP as an energy source. Tricarboxylic acid (Krebs) cycle - pyruvate and ATP both to provide further energy and to form intermediate substances for amino acid and fatty acid biosynthesis. knof Biosynthetic pathways Purine synthesis, Pyrimidine synthesis, Amino acid synthesis  Catabolic pathways Breakdown of large molecules in a series of sequential steps coupled to reactions that store energy in small energy carriers such as ATP and NADH. + AT + -AD + fi ATP stores energy in the bonds formed by condensation of ADP with inorganic phosphate (Pi). Hydrolysis of these bonds yields energy. NADH stores energy associated with a pair of electrons that can reduce a substrate, such as a protein of the electron transport system (ETS). Oxidizing NADH to NAD+ yields energy and transfers two electrons (2e–) to a substrate molecule. Pathways of Catabolism  Schemes for producing energy In bacteria: EMP (glycolysis), the tricarboxylic acid cycle, and oxidative phosphorylation. Facultative organisms can live under aerobic or anaerobic conditions. Obligate aerobes are restricted to the use of oxygen as the final electron acceptor, is called “respiration”. wor Anaerobes (growing in the absence of molecular O2) use the process of “fermentation”. pyruvate to form waste products that are excreted from the cell. Sugar fermentation and organic acid respiration are used as tools in diagnostic media to identify pathogens.  wine Many end products use for food or = industry. O E Cdi. Electron transport system (ETS), which ultimately transfers electron to O2 The final electron transfer, and energy capture for ATP, occurs through the ETS and the membrane-embedded ATPase. To build something complex requires spending energy (ATP). The cell membrane is the site of oxidative phosphorylation (or respiration)  The Growth Cycle Cell Division Binary fission, one parent cell splits into - multiply by binary fission two equal daughter cells. 2- 4-8 Budding, one end to produce small, unstalked cells that then break off from the parent cell.  Binary Fission and Cell Cycle 1. A parent cell at the beginning of the cell cycle 2. Chromosome replication and cell enlargement 3. Chromosome division and septation 4. Chromosome of cell compartment 5. End of cell division cycle --  Common Cell Arrangements Chains Packets Clusters T and 857276 ↓ panel Generation Time: the rate of bacterial growth - E. coli in nutrient broth will replicate in 20 minutes. - Mycobacterium tuberculosis has a doubling time of 14 hours. If a bacterium has a generation time of 20 minutes, and you start with 100 cells at time 0, how many cells will you have in 4 hours? For the calculation, simply multiply the number present initially × 2n, with “n” being the number of generations at that point. [ 100 x 29 (1 generations), 100 x 21 (2 generations), 100 x 22 (12 generations), 100 x 212 (3 generations), 100 x 23 = 409,600 (4 generations), 100 x 24  acumnividon y Bacterial Growth Curves - In the laboratory, many microorganisms are grown either on agar plates or in tubes or flasks of broth. These are considered closed systems, or batch cultures, ·bin Ju Agas N A Ste Lost 9 T & Die gocW jor] Loc ~ prepare t  ↳ unneede C - - E - C C In80 40 win zomin 60 20 time - lig ⑫ 2 x 24 = 32 : Bacterial growth correlates to disease Relationship between environmental factors and growth rate ~ esord - - -  Temperature - Most pathogenic bacteria grow best at 37 ◦C - C. jejuni, it is 42 ◦C. - Listeria monocytogenes, a cause of food poisoning, will grow slowly at 4 ◦C. The Effects of Sodium Chloride on Microbial Growth in More Osmolarity Oxygen requirements C Mycobacteria, Enterobacteriaceae Clostridium spp., Campylobacter spp. Pseudomonas spp. family, Streptococci, Bacteroides spp. Helicobacter pylori and some fungi. Staphylococci spp., (normalgastrointe Lactobacillus Bacillus anthracis spp. stinal flora).  Environmental Limits on Microbial Growth Temperature affects the average rate of molecular motion, changes in temperature impact every aspect of microbial physiology, including membrane fluidity, nutrient transport, DNA stability, RNA stability, and enzyme structure and function. Variations in pressure, high pressure can kill these bacteria, many food processes are carried out at high pressure to minimize bacterial contamination. Water availability and salt concentration, the more solutes in a solution (for example, the higher the salt concentration), the less water is available for microbes to use for growth.  Bacterial cultivation The propagation of bacteria based on their specific pH oxygen requirements temperature preferences. It is performed in either liquid (broth) or solid (agar) growth medium and requires an environment that contains (1) Carbon source (4) Inorganic salts (2) Nitrogen source (5) Growth factors (3) Energy source (6) Electron donors and acceptors  Growth media 1. Minimal essential growth medium This medium contains only the primary precursor compounds essential for growth. A bacterium grown in this medium must synthesize most of the organic compounds required for its growth. Nutrient broth/nutrient agar that contains ‘peptone’ (polypeptides and amino acids from the enzymatic digestion of meat) and Generation time is relatively slow. ‘meat extract’ (water-soluble components of meat containing mineral salts and vitamins).  Growth media anzi othtrokoz - - 2. Complex growth medium (Enriched) This medium contains most of the organic compound building blocks (e.g., sugars, amino acids, nucleotides) necessary for growth. Generation time for a bacterium is faster relative to its generation time in minimal essential medium. Fastidious bacteria are grown in this medium. agar containing whole blood (blood agar) or agar containing lysed blood (chocolate agar).  Growth media -is lactose jalia" 3. Differential growth medium ~ This medium contains a combination of nutrients and pH indicators to allow the visual distinction of bacteria that grow on or in it. have a distinctive color. / Colonies of particular bacterial species fermentation lactaser i  gastute's Growth media aureus 1 Birius Eu miniscen 4. Selective growth medium This medium contains compounds that prevent the growth of some bacteria while allowing the growth of other bacteria. Dyes or sugars, antibiotics, high salt concentration, or pH are Mannitol salt agar which contains increased NaCl used to achieve selectivity. (salt) concentration for the recovery of staphylococci Differential and Selective Growth Medias  Physiological Characteristics: Oxidation and Fermentation Tests Knowledge of enzymatic reactions, substrates, and end products. Determine if your unknown is metabolically oxidative or fermentative by performing the appropriate diagnostic tests.  251 Oxidation and Fermentation Tests Durham tubes: (a) uninoculated control; (b) alkaline; (c) acid, no gas; (d) acid, gas. Determining an organism’s ability to catabolize various substrates. Clinical Tests based on fermentation. Biochemical Tests (organism produces enzymes in response to the presence of certain substrates) such as Oxidase, Coagulase, Catalase, Hemolysin. Categories of culture media include enrichment media, enriched media, selective media, and differential media. Some bacteria produce enzymes called hemolysins that damage or destroy red blood cells. Separation outline for gram-positive rods and cocci Separation outline for gram-negative rods and cocci Separation outline for facultatively anaerobic gram-negative rods  Effects of Osmotic Pressure on Bacterial Growth into y ~ When the diffusion of water molecules occurs across a semipermeable membrane, such as a cell membrane, the process is called osmosis, and the pressure created by the flow of water into the cell is known as osmotic pressure. Osmosis and Water Balance Hypotonic environment (lower concentration of solutes outside the cell), the cell swells with water, and the cell components are diluted. The cell is destroyed by lysis. Hypertonic (higher concentration of solutes outside the cell), causes net loss of water from a cell. The cell shrinks, and the concentration of cell solutes (inorganic ions as well as organic molecules) increases.  Bacterial Membranes and Transport Bacterial Membrane Proteins - Structural support - Detecting environmental signals sett - Secreting virulence factors and Communication signals - Transport across the cell membrane such as transport proteins for sugars and amino acids. - Energy storage and transfer  Membranes and Transport Membranes are selectively permeable, they are permeable to some substances but not to others. Diffusion across the membrane also depends on the size of the molecule, is the movement of molecules from an area of high concentration to one of low concentration. Osmosis is the diffusion of water across a selectively permeable membrane from regions of high water concentration (low solute) to regions of low water concentration (high solute).  Passive Transport e substand Active transport  nairo-it 1. Explain how nutrition and the environment can impact microbial growth and differentiation. 2. Discuss microbial classifications based on nutritional needs and environmental limits. importin intussul 3. Describe how understanding Isone microbial growth helps identify Isab disease-causing pathogens. [email protected] O  Elements, Bonding, and Water 1. Which atom is not an essential 2. Which compound would C part of most living cells? dissolve poorly in water, A. Carbon - compared => with lipids? ~ B. Hydrogen - A. Butane (CH3CH2CH2CH3) C C. Oxygen - B. NaCl - iron - D. Nitrogen C. Glycine E. Helium L D. CO2 C 3. Which compound would dissolve in water by forming ions? O A. NaCl 2n B. O2 C. Glycine D. CO2  Lipids and Sugars 4. Which part of a lipid is the most 5. A simple sugar contains all of these types & hydrophobic? of chemical structures, except for _____. 9 ↑ - A. Glycerol A. a carbonyl group B. Hydrocarbon chain H e => B. a hydroxyl group C. Carboxyl group C. an amino group C D. Ester linkage of a triglyceride D. a carbon-carbon bond 6. Which molecule contains sugar components? A. Fatty acid B. Methane C. Glycine D. Glycoprotein G  Nucleic Acids 7. A nucleotide contains all of these 8. Which molecule is usually a chemical structures, except for _____. component of RNA but not DNA? 0- A. a thiol (–SH) - C A. Uracil B. a phosphoryl groupV B. Cytosine A+ C C. a nucleobase C. Guanine D. a pentose sugar ~ D. Adenine  Biochemical Reactions 9. Which process does not yield 10. For an intestinal bacterium, which factor energy for a cell? I c'd mos sic is most likely to increase the rate of a A. DNA synthesis - - C reaction catalyzed by an enzyme? B. Oxidation of sugar - A. Decreasing concentration of the substrate C. Oxidation of lipids - B. pH increase from pH 8 to pH 9 D. Breakdown of carbohydrates C. Salt saturation into smaller molecules C D. Increase in temperature - = from 25°C to 35°C - 11. Which molecule from glucose catabolism directly enters the TCA cycle? O A. Acetyl-CoA B. Fructose 1,6-bisphosphate C. Glyceraldehyde 3-phosphate D. Glucose  Membranes and Transport 12. Which molecule requires a 13. Which process& -- involves osmosis? transport protein in order to A. A transport protein carries a nutrient cross a membrane? across a membrane. A. H2O B. CO2 crosses a membrane. B. O2 & C. A cell placed in distilled water takes up - O C. Alanine water - and expands. D. Ethanol D. A protein is synthesized in the cytoplasm.