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Oxygen not required or may even be toxic to microbeMICROBIOLOGY OUTLINE:Exam 2CHAPTER SEVEN (all): Microbial Nutrition and Growth I. Microbial Nutrition- Elements- Major bioelements= C, H, N, O, P, S- Minor bioelements= Ca, Na, K, Cl, Fe- Micronutrients= Mn, Zn, Cu, others (metals) used for a few types ofchemical reactions; too much of these can be toxic- Molecules- Organic Biomolecules Types1.) Proteins2.) Carbohydrates3.) Lipids4.) Nucleic Acids Many are macromolecules Synthesized from smaller inorganic or small organic molecules Growth Factors organic molecule that cannot be synthesized andmust be taken into the cell from the environment**Vitamins are growth factors- Vitamin A you can’t synthesize; must get it from dietII. How do Microbes Acquire Nutrients?- Transport across cell membrane- Small inorganic and organic molecules Salt (ions), simple sugars, amino acids (Ca, Na, K) Carbon dioxide- Most bacteria and Fungi, many protozoa transport across cell membrane- Acquiring Nutrients from large Molecules- Bacteria and Fungi, and some protozoa secrete enzyme outside of cell (degredative enzyme) enzyme breaks down large molecule into smaller molecules of nutrients that can be transported across membrane- Phagocytosis and Injection- Some Protozoa** Particle or liquid sits in vesicle until digested once degraded into smaller particles vesicle releases the particles Pinocytosis= engulfing liquid Phagocytosis= engulfing particlesIII. Metabolic Categories- Autotroph = a microorganism that requires only inorganic nutrients and whose sole source of carbon is carbon dioxide- “Self-feeder”- Use CO2- Heterotroph = an organism that relies upon organic compounds for its carbon and energy needs- “Other feeder”- Use organic materials to get CO2- Photoautotroph = an organism that utilizes light for its energy and carbon dioxide chiefly for its carbon needs- Chemoautotroph = an organism that relies upon inorganic chemicals for its energy and carbon dioxide for its carbon (also called a chemolithotroph)- Chemoheterotroph = Microorganisms that derive their nutritional needs from organic compoundsIV. Types of Chemoautotrophs1.) Predators actively capture food- some protozoa, few bacteria and fungi; usually takes place in soil2.) Saprobes decomposers; grow on dead material- (saphoritic)3.) Commensals use living organisms to get food cell- bacteria, protozoa, fungi4.) Parasites harms organisms they are growing on or in ( pathogens)- bacteria, fungi, protozoa, virusesV. Bacterial Growth- Microbiologists measure the growth of a population- Types of growth:1.) Open system : system where some microbe has unlimited space to grow, unlimited nutrients, no build up of waste products2.) Closed system : limited space, limited nutrients, waste product build upVI. Method of Reproduction- Binary Fission bacteria splits to reproduceVII. Growth in Open System- Doubling or exponential growth- 1-2-4-8-16-32- Doubling time (generation time)= time required for the population to double in sizeVIII. Growth in Closed System- standard/normal growth curve1.) Lag phase = “gearing up” phase2.) Exponential Growth Phase = doubling growth3.) Stationary Phase = where cells start to die4.) Death Phase = more cells dyingIX. Methods of Enumeration1.) Standard Plate Count - Colony forming units2.) Turbidity - way of estimating growth in a liquid- the more bacteria there are in a flask, the cloudier the water is (more turbid)- Spectroturtometer= instrument that measures the turbidity of liquids3.) Direct Count Microscopy - look under microscope- count number of cells on grid4.) Flow Cytometry - look at how many cells by way of an electric detector hooked up to a computer; used a lot in hospitals (can count blood cells)X. Factors Influencing Growth- Nutrient limitation, waste accumulation, physical space- Other physical and chemical forces- temperature- oxygen levels- hydrogen ions (pH)- Osmotic Forces (salt concentration)- growth response- microbes grow best (optimum growth) at one point of an environmental factorXI. Temperatures Effects on Growth- Enzymes chemical reactions in body- effects rate of catalysis higher temperature  higher rate (twice as fast per 10 degrees C) - high temperatures will eventually degrade proteins and enzymesXII. Membrane Fluidity: how easily molecules move around in membrane- The higher the temperature the lower the fluidity- High temperatures melt/disintegrate membraneXIII. Temperature Ranges for Microbial Growth- 0 degrees C= freezing point of water; 100 degrees C= boiling point of water- Categories of Microbial Growth1.) Psychrophile  “cold loving” have optimum growth at very cold levelso Best around 4 degrees C2.) Mesophile  “mid-temperature loving” have optimum growth at mid temperatureso Best around 37 degrees C= human body temp3.) Thermophile  “hot loving”o Best around 65-70 degrees C4.) Hypothermophile  “extreme heat loving” optimum growth at very hot temperatureso Best around the boiling point of water; 100 degrees C- Chlamydomonas nivalis= a Eukaryotic psychrophile; protozoaXIV. Oxygen’s Effects of Microbial Growth- Oxygen is needed for energy metabolism (cellular respiration) by some microbes- Must be able to deal with toxic 02 derivatives Super oxides, peroxides, others- Have enzymes to remove toxic derivatives Superoxide dismutase Catalae and peroxidase- Other microbes use alternate energy pathways that do not require oxygen (fermentation and anaerobic respiration)- Oxygen not required or may even be toxic to microbe- Lack of dismutase and catalase enzymesXV. Determining Oxygen Requirement- High 02 at the top of tube and no 02 at the bottom of the tube see where bacteria growth occurs in the liquid= oxygen preference- Study FIGURE1.) Obligate Aerobe  likes high 02 levels; atmospheric levels2.) Faculative Anaerobe  can grown without 02 but grows very well with high 023.) Aerotolerant Anaerobe  can grown without 02 but no preference for particular level4.) Strict Anaerobe  needs reduced to no 02 to growXVI. Other Environmental Factors Influencing Growth- Hydrogen ion concentration (pH)1.) Alkaphile alkaline or basic conditions2.) Acidophiles acidic conditions- Salts- Halophiles grow at 15-22% salt concentration- Normal salt concentration = 0.9% concentration for microbial growth- Pressure- Barophile


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KSU BSCI 20021 - Exam 2

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