Chapter 4: Dynamics of Prokaryotic Growth
Chapter 4: Dynamics of Prokaryotic Growth MICRBIO 4000 - 0110
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This 11 page Class Notes was uploaded by Victoria Gonzalez on Sunday September 27, 2015. The Class Notes belongs to MICRBIO 4000 - 0110 at Ohio State University taught by Madhura Pradhan,Tammy Bullwinkle in Fall 2015. Since its upload, it has received 21 views. For similar materials see Basic and Practical Microbiology in Microbiology at Ohio State University.
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Date Created: 09/27/15
Chapter 4 Dynamics of Prokaryotic Growth Victoria Gonzalez Key concepts Binary ssion Exponential growth how to calculate doubling time 5 phases of bacteria culture growth What pure cultures are and how they re obtained Environmental conditions that will affect microbial growth and how organisms are categorized based on their tolerances of these conditions Nutritional requirements for microbes and how microbes are categorized based on carbon and energy sources Complex vs chemically de ned media Selective vs differential medias some medias are both Different methods we use to detect and measure growth of bacteria in the laboratory Terms Exponential log phase in a bacteria growth curve stage in which cells multiply exponentially Generation time time it takes for the number of cells in a population to double doubling time Bio lm polymer encased community of microorganisms Chemically de ned medium a culture medium composed of exact quantities of pure chemicals generally used for speci c experiments when nutrients must be precisely controlled Complex medium a culture medium that contains protein digests extracts or other ingredients that vary in their chemical composition Differential medium a culture medium with an ingredient that certain microorganisms change in a recognizable way used to differentiate microbes based on their metabolite traits Selective medium a culture medium with an ingredient that inhibits the growth of microbes other than the one being sought Facultative anaerobe organism that grows best if oxygen is available but can also grow without it Obligate aerobe organism that requires molecular oxygen Obligate anaerobe organism that cannot multiply and is often killed in the presence of oxygen Microaerophile organisms that require small amounts of oxygen for growth and are inhibited by higher concentrations Aerotolerate anaerobe organism that can grow in the presence of oxygen but never uses it as a terminal electron acceptor an obligate fermenter Plate count method to measure the concentration of viable cells by determining the number of colonies that develop from a sample added to an agar plate Pure culture a population of organisms descended from a single cell Autotroph organisms that uses carbon dioxide as its main carbon source Hetertroph organisms that obtains carbon from an organic compound such as glucose Phototroph organisms that use light as a source of energy Chemotroph organisms that obtain energy by oxidizing chemical compounds 1 Binary ssion how bacteria divides Chromosome begins to replicate Chromosomes move to opposite ends a b c d e Cell doubles all components Plasma membrane pinches inward with the help of FtsZ Cytoplasm is split new cell membrane is synthesized 1 Two daughter cells result exponential growth 2 Timing is regulated a Generation Time the time it takes for a population to double b 1 No X 2quot N number of cells in a population at a given time No original number of cells in population N number of doublings in that time c Measured during exponential growth log phase d In a closed system growth begins exponentially but then resources run out the growth plateaus and then bacteria begin to die Lag phase cells begin making enzymes needed for growth Log phase cells are dividing constantly exponential primary and secondary metabolites are made Stationary phase nutrient levels become low rate of death and division are the same some cells use nutrients released by other dead cells in order to multiply Death phase cells are dying off at a constant rate exponenUaD Prolonged decline phase some cells are able to adapt or tolerate the worsened conditions may give rise to a tter population e Batch culture formed in a closed system f Continuous culture formed in an open system 3 Growth in nature a Cooperative interactions Growth of species otherwise unable to survive Strict anaerobes can grow in the mouth if others consume oxygen Metabolic waste of one nutrient for another b Competitive interactions Synthesize toxic compounds to inhibit competitors Some gramnegatives use the needle like type Vl secretion system to inject toxic compounds directly c Bio lms working together Polysaccharideencased communities 1 Slippery rocks in rivers 2 Scum in toilets 3 Dental plaque ii Secretion is tightly regulated cells sense other cells through signaling chemicals iii More resistant to disinfectants iv Can pass nutrients through channels between cells v Bio lm formation 1 Bacteria move on surface and adhere 2 Bacteria multiply and produce extracellular polymeric substances EPS 3 Other bacteria may attach to EPS and grow 4 Cells communicate and create channels in EPS that allow nutrients and waste products to pass 5 Some ces detach and move creating additional bio lms d Pure culture in lab population descended from a single cell therefore separated from other species or strains i A single cell can multiply and form a visible colony ii Growth in petri dish allows air excludes contaminants iii Agar is used to solidify can be sterilized few microbes can degrade agar iv Many microbes don t grow well in lab conditions v Lab conditions are likely not good mimics of the environment vi Stock cultures 1 Refrigerator as agar slant 2 Frozen at 70C 3 Freeze dried 4 Factors that affect growth a Temperature i From coldest to hottest Psychrophile coldest arctic and antarctic Psychrotroph spoilage in refrigerated foods Mesophile most human pathogens Thermophile hot springs and compost heaps Hyperthermophile hottest usually archaea U39lbUUNl l e agi atn afmji39sj 14 ENE i Ili39IEth iEZvu39iijiiiiv quot Em imnmental Fathers That 39cruhiv 39 raw39th 7 j Influence 7 its 1 19 339 7 7 7 L HfVa if ii i i g iji titlt r f appears ta be due ta wrotein Mh mpliie p mum and zar f39 uFtF quot Fewhrh ptimum be eern and but em 39 W z A 77503 9351339 7 7 HamelNile mum nudism WEAIBFJF I I 39 p mttm temperature an 113 1589 Hype he m hil e pt imum temperature at nr39 Enzymes must be adapted to live in this temperature jii iieuzmttr a TABLE 133 b Atmosphere oxygen content I ii iii iv v Aerobic respiration oxygen is an electron acceptor Anaerobic respiration doesn t use oxygen Obligate necessary Facultative exible Almost all organisms that grow in the presence of oxygen produce 1 Superoxide dismutase converts superoxide into oxygen and hydrogen peroxide 2 Catalase converts hydrogen peroxide into oxygen and water Obligate aerobe 1 Grows only when oxygen is available Facultative anaerobe 1 Grows best With oxygen can grow without it Obligate anaerobe 1 Cannot grow in the presence of oxygen 2 Often dies when exposed to oxygen 3 Does not produce superoxide dismutase or catalase Microaerophile 1 Require small amounts of oxygen 2 Too much oxygen inhibits growth Aerotolerant anaerobe 1 Grows well with or without oxygen 2 Doesn t use the oxygen for growth 3 Produces superoxide dismutase but not catalase i Enzymes must be able to function ii Acidophiles pH below 55 iii Neutrophiles pH 5 pH 8 most microbes 1 Pickling inhibits bacteria growth by making more acidic iv Alkaliphiles pH above 85 v Extremeophile organism in pH that would kill most others 1 Usually archaea e Water content salt concentration i All microorganisms need water for growth ii Plasmolysis when solute concentration in the medium is higher than in the cell water rushes out of the cell The cytoplasm detaches and shrinks away from the cell wall 1 Adding high levels of salt or sugar is used for food preservation ex bacon anchovies iii quotHaloquot salt iv Halotolerant can grow in relatively high salt solutions 1 Staphylococcus and Listeria Monocytogenes live on dry salty skin v Halophile requires high levels of sodium chloride f Nutritional factors i Microbes require nutrients to synthesize cell components 1 Lipid membranes cell walls proteins and nucleic acids are made from lipids sugars amino acids nucleotides ii Major elements carbon hydrogen oxygen nitrogen sulfur phosphorous potassium magnesium calcium iron 1 Essential components of proteins lipids carbohydrates and nucleic acids ThEILE 4 I Representa I Majnr Elem iii Nitrogen xation converting nitrogen gas into ammonia which can be incorporated into cellular material 1 Unique to prokaryotes 2 Essential to life because nitrogen is a component of amino acids and nucleic acids iv Phosphorous and Iron are often limiting nutrients available at the lowest concentration one needs v Trace elements required in a very small amount 1 Cobalt zinc copper manganese g Energy source sunlight i Heterotroph use organic carbon 1 Pathogenic bacteria are heterotrophic they cannot produce their own energy and therefore use the carbon found in human cells ii Autotroph use inorganic carbon in the form of carbon dioxide photosynthesis 1 They convert inorganic carbon into an organic form through carbon xation Without it the earth would run out of organic carbon essential to life iii Phototrophs obtain energy from sunlight iv Chemotrophs extract energy from chemical compounds v Types to know 1 Photoautotroph a Obtains energy from sun photo b Gets carbon from inorganic C02 auto 2 Photoheterotroph a Obtains energy from sun photo b Gets carbon from organic compounds hetero 3 Chemolithoautotroph a Obtains energy from inorganic chemicals such as H2 NH3 chemo b Gets carbon from inorganic C02 auto 4 Chemoorganoheterotroph a Obtains energy from organic compounds such as sugars and amino acids chemo b Gets carbon from organic compounds hetero 5 Media in the laboratory a Complex media contains nutrient rich ingredients like meat juices and digested protein exact chemical compositions are variable 10 b Chemically de ned media contains exact amounts of pure chemicals Useful in research because nutrients can be accurately controlled c Selective media inhibits growth of certain species making it easier to isolate a colony or species of interest i Ex Antibiotic media will only allow the growth of bacteria that is resistant to speci c antibiotic d Differential media changes certain species of microbes in a recognizable way i Ex Blood agar allows to identify bacteria that can lyse red blood cells 6 Growth in the laboratory a Growth factor molecule available in an organism s surroundings that allows it to grow b Fastidious organism with complicated nutritional requirements c Atmospheric conditions can be controlled i Atmospheric chambers for agar plates ii Glove box that removes oxygen d Enrichment culture i Medium and incubation conditions that favour growth of one species over another Helps narrow down a species if it isn t present in high numbers in a mix population 7 Detecting and measuring growth a Direct cell counts most cases includes all cells living and dead i Direct microscope count ii Cell counting instruments b Viable cell counts count living cells or those capable of multiplying plate counting units cfu colony forming units c Membrane ltration for liquids with few cells Cells are concentrated by ltration before moved to a plate i Water purifying plants use this method d Measuring biomass turbidity or weight is measured using a spectrophotometer See how much light goes through cuvette e Detecting cell products i Acid and gas production indicators of metabolism living cells Can use pH indicators or durham tubes to trap gas bubbles in tube cultures ii ATP measuring catabolism can be detected using re y enzyme luciferase in living cells 1 Luciferace uses ATP to catalyze light producing reaction 11