Microbial Growth And Nutrition - Lecture 6 PDF

6/16/24 Lecture 6 Microbial Growth and Nutrition Introduction to Metabolism Reading: Chapter 7 Section 5 Chapter 3, Pages 50-54 Chapter...

6/16/24 Lecture 6 Microbial Growth and Nutrition Introduction to Metabolism Reading: Chapter 7 Section 5 Chapter 3, Pages 50-54 Chapter 10 Sections 1-6 Environmental Factors Influence Microbial Growth. Let’s consider a few. Oxygen Concentration Temperature Solutes and Water Activity Microbes that grow in extreme environments are called extremophiles Copyright © McGraw-Hill Companies, Inc. Permission required for reproduction or display. Microbes Can Grow Under a Wide Range of Oxygen Concentrations need prefer ignore oxygen is oxygen oxygen oxygen toxic more O2 2-10% Obligate less O2 anaerobe 3 Figure 7.20 1  6/16/24 Copyright © McGraw-Hill Companies, Inc. Permission required for reproduction or display. What is the basis of different oxygen sensitivities? oxygen can be reduced to toxic products called Reactive Oxygen Species. Examples include superoxide radical (O2-) and hydrogen peroxide (H2O2). Microbes that live in the presence of oxygen need enzymes to detoxify. · Enzymes = S Catalase positive - Superoxide dismutase (SOD) 02 H202 02 * + 02 + 2H > - + - Catalase H2O2 + HzO2 > - 2H20 + O2 4 Catalase negative Microbes can grow under a wide range Copyright © McGraw-Hill Companies, Inc. Permission required for reproduction or display. of temperatures Hyperthermophiles grow between 85 and 113oC Pink Snow Thermophiles between 45-85oC Ex Thermus aquaticus (bacterium) Source of Taq Polymerase Mesophiles % · 20-45 C Ex : Escherichia coli Snow Algae Genus: - % 0-20 C · Psychrophiles 2 Chlamydomonas - 5 EX: High temperature disrupts membranes, denatures proteins and DNA. How do thermophiles adapt? Proteins stabilized – increased hydrogen and covalent bonds – molecular chaperones – bind, refold damaged proteins DNA stabilized – synthesize proteins to coat DNA Membrane stabilized, how? lipids 6 with ether instead of ester linkage 2  6/16/24 Copyright © McGraw-Hill Companies, Inc. Permission required for reproduction or display. Microbes can grow under a wide range of solute concentrations ~ - solutes such as salts and sugars decrease the availability of water to microbes availability of water affects growth of all cells expressed as: water activity (aw) higher [solute] ---> lower aw 7 Movement of water in and out of bacterial cells by osmosis ⑧ Low extracellular solute con. = hypotonic. ⑧ Fresh water lake or stream ⑳ Same solute con. in and out = Isotonic ⑧ Hypertonic = high extracellular solute con.. · Low a y Dead Sea, great salt Lake, peanut 8 ⑧ butter 0:00 Solute Concentration and Water Activity Halophile – require high [salt] to grow Osmotolerant – grow over wide range of aw Ex: – Staphylococcus – salt tolerant commensal of human skin – Mannitol Salt Agar to select Xerophile - grow best at low a W -Cronobacter - dry conditions - How do microbes survive in highly concentrated environments? -> Use Compatible Solutes Ex: potassium chloride, betaken, some amino acids (proline) 9 3  6/16/24 Phone record at 11:00 Microbial Nutrition microbese to obtain energy and construct new cellular components, microbes must have a supply of raw materials and nutrients nutrients - substances used in biosynthesis and energy release - required for growth 10 12:36. 95% of the microbial cell dry weight is made up of a few major elements ! Macronutrients (or macroelements) ⑳ I Required in large amountsY - EX C, O, H, N, S, P, Fe : Micronutrients (or trace elements) · ES 7 Required in small amounts = Ex cobalt, copper, zinc, manganese : Cobalt 11 C Zu Mr Lets look at nitrogen. What sources can microbes use? Root nodules formed Microbes can use Ammonia by Rhizobium (NH3) or Nitrate (NO3) Explain the use of A fee use nitrogen gas (N2) - 79% nitrogen fix ~18:00 of earth's atmosphere 9 ↑ Nitrogen fixation - N2 reduced to ammonia. Rhizobium - in symbiosis with plants Azotobacter - free living in soil 12 4  6/16/24 20:00.~ Obtain Acquiring Nutrients Rapid growth of microbes presents challenges in acquiring nutrients Food must enter: – at high rates – across membranes – selective fashion – often against concentration gradient Passive and Active transport systems used 13 25:00 ~ Passive Transport Facilitated Diffusion No energy required Fig. 3.11 Requires gradient from [higher] to [lower] H - H -> L Passive Diffusion – only small molecules and certain gases ⑳ Facilitated Diffusion – Uses membrane carrier proteins ↑ 14 Active transport Energy - dependent Moves nutrients against gradient PMF ATP or proton motive force used such as proton something 2 types- primary and secondary 15 5  6/16/24 32:00 ATP binding Cassette Primary Active Transport: ABC Transporters stay here , nutrient nutrient b ↳ more only > - transfer against the gradient Fig. 3.13 16 ABC Transporters are found in all domains of life and can move substances in or out of cells. Uptake ABC – move nutrients in Export ABC – also called Multidrug Efflux Pumps, move substances out In bacterial cells - move antibiotics out, bacteria become resistant to antibiotic Good In cancer cells - move anticancer drugs out, tumor becomes resistant Bad Survive 17 Secondary Active Transport Uses potential energy Example: Lac Permease of ion gradients Membrane protein, moves lactose in powered by Electron transport proton also moving in across membrane generates proton (H+) gradient – Can use gradient to do work! Fig. 3.12 6  6/16/24 43:12 Active Transport: Group Translocation Don't memorize Example: Phosphotransferase X system in bacteria Nutrient chemically altered Energy from phosphoenolpyruvate attaches · P to sugars Phosphoenolpyruvate - key Fig. 3.14 intermediate in Glycolysis Metabolic pathway that convert glucose to pyruvate 19 47:15 Iron Uptake Fig. 3.15 Problem: All microbes require iron (Fe), but there is little free Fe available, often insoluble form (ferric iron, Fe3+) Solution: microbes release siderophores to acquire Fe Siderophore - Fe complex then Enterobactin: An Escherichia transported into cell often using coli siderophore ABC Transporters 20 Siderophore- iron complex transport into a gram- negative bacterial cell End at 49:28 7  6/16/24 Introduction to Metabolism Metabolism - all chemical reactions in a cell Catabolism - breakdown of complex molecules into smaller ones with release of energy for Anabolism – reactions that build cells 22 Metabolism requires a flow of energy (capacity to do work) and the participation of enzymes. ATP is the energy currency of cells. 23 Adenosine Triphosphate (Fig. 10.2) P removal - large negative standard Adenosine free energy change Sugar 24 8  6/16/24 The Cell s Energy Cycle Energy ATP by Oxidative Phosphorylation Generating Systems ~ - - ATP by Substrate-Level ATP by Phosphorylation Photophosphorylation 25 Fig. 10.4 Metabolism Requires Enzymes Proteins (often) that catalyze reactions – Ribozymes are catalytic RNAs Act on substrates, convert to products Activation energy – energy required to bring reacting molecules together Enzymes increase reaction rates by lowering activation energy Often named for reactions they catalyze – Phosphatase, Kinase, Cellulase 26 06:27 How do enzymes lower the energy of Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. activation? Increase local concentrations of substrate orient substrates properly for reactions to proceed 27 9  6/16/24 Metabolism Involves Oxidation-Reduction (Redox) Reactions and Electron Carriers electrons move from donor to acceptor utilize carriers redox reactions can result in energy release, which can be used to form ATP 28 Oxidation-Reduction Reactions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oxidation - removal of electrons Reduction- addition of electrons Substance oxidized is donor, substance reduced is acceptor (pair = redox couple) oxidation-reductions often involve not just the transfer of electrons but both an electron + proton (H atom, example: NAD+/NADH) 29 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Reduction Potential (E0) equilibrium constant for redox reactions measures tendency of donor to lose electrons More negative E better donor O more positive E better acceptor 8 30 10  6/16/24 Half reactions are written as: Acceptor + #e -> Donor Redox couple (or pair) Couples with more negative Eo will donate e- to couples with more positive Eo 31 17:40. The Electron Tower Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oxidation Greater the difference z The more energy released! 32 Figure 10.5 Reduction 21:40 Electron Carriers in Redox Reactions Can be Divided into Two Classes Freely diffusible (in cytoplasm) – Examples: NAD+ and NADP+ – Reduced forms (NADH, NADPH) are the Reducing Power of the cell Membrane-bound – Examples: flavoproteins, cytochromes, quinones – Important components of Electron Transport Chains 33 11  6/16/24 Half reactions are written as: Acceptor + #e -> Donor Redox couple (or pair) 31 The Electron Tower Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 32 Figure 10.5 Electron Carriers in Redox Reactions Can be Divided into Two Classes Freely diffusible (in cytoplasm) – Examples: NAD+ and NADP+ – Reduced forms (NADH, NADPH) are the Reducing Power of the cell Membrane-bound – Examples: flavoproteins, cytochromes, quinones – Important components of Electron Transport Chains 33 11