Slide 1Chapter 5 SummaryWhy is this important?Growth RequirementsSources of Carbon, Energy, and ElectronsSources of Carbon, Energy, and ElectronsOxygen RequirementsOxygen RequirementsOxygen RequirementsOxygen RequirementsOxygen RequirementsNitrogen RequirementsOther Chemical RequirementsOther Chemical RequirementsPhysical RequirementsTemperatureTemperatureTemperaturepHPhysical Effects of WaterOsmotic PressureHydrostatic PressureAssociations and BiofilmsAssociations and BiofilmsBiofilmsGrowth of Microbial PopulationsGrowth of Microbial PopulationsGrowth of Microbial PopulationsMathematical Considerations in Population GrowthGeneration TimePhases of Microbial Population GrowthPhases of Microbial Population GrowthLag PhaseLog PhaseStationary PhaseDeath PhaseM I C R O B I O L O G YWITH DISEASES BY BODY SYSTEM SECOND EDITIONChapter 6Microbial Nutrition and GrowthTHIRDChapter 5 Summary•Metabolism – the set of controlled chemical reactions within cells•The ultimate outcome of metabolic activity is reproduction–Reproduction is an increase in the number of individual cells or organisms•Growth refers to an increase in the size of a population of microbes rather than to an increase in the size of an individual–Result is a discrete colony (an aggregation of cells arising from a single parent cell) or a biofilm (a collection of microbes living on a surface in a complex community)Why is this important?•Microbial growth is a result of microbial metabolism.•Different organisms require different nutrients for growth•Different organisms also require different growth conditions for growth (applications to human health)•Knowing what a microbe requires for growth allows us to grow them in the labGrowth Requirements•Organisms use a variety of nutrients for their energy needs and to build organic molecules and cellular structures•Most common nutrients – those containing necessary elements such as carbon, oxygen, nitrogen, and hydrogen•Microbes obtain nutrients from variety of sources and they must bring nutrients into their cells by the passive and active transport processes discussed in Chapter 3Sources of Carbon, Energy, and Electrons•Two groups of organisms based on source of carbon–Autotrophs – inorganic source of carbon (carbon dioxide) –Make organic compounds from carbon dioxide–Not nutritionally dependent on other living things–Heterotrophs – catabolize reduced organic molecules (proteins, carbohydrates, amino acids, and fatty acids)–Dependent upon other life forms•Two groups of organisms based on use of chemicals or light as source of energy–Chemotrophs acquire energy from redox reactions involving inorganic and organic chemicals–Phototrophs use light as their energy sourceSources of Carbon, Energy, and ElectronsOxygen Requirements•Oxygen is essential for obligate aerobes (final electron acceptor in ETC), but deadly for obligate anaerobes•How can this be true when neither gaseous oxygen nor oxygen covalently bound in compounds is poisonous?–The forms of oxygen that are toxic are highly reactive and also excellent oxidizing agents–Resulting chain of oxidations causes irreparable damage to cells by oxidizing compounds such as proteins and lipidsOxygen Requirements•Four toxic forms of oxygen1. Singlet oxygen – molecular oxygen with electrons boosted to higher energy state–Phagocytic cells (certain WBC) use it to oxidize pathogens–Occurs during photosynthesis so phototropic organisms have carotenoids that remove the excess energy of singlet oxygen2. Superoxide radicals – some form during aerobic respiration and anaerobic metabolism occurring in the presence of oxygen–So reactive that aerobes must produce superoxide dismutases to detoxify them–Anaerobes lack superoxide dismutase and die as a result of oxidizing reactions of superoxide radicals formed in presence of oxygenOxygen Requirements•Four toxic forms of oxygen3. Peroxide anion – formed during reactions catalyzed by superoxide dismutase and other reactions–Aerobes contain either catalase or peroxidase to detoxify peroxide anion–Obligate anaerobes either lack both enzymes or have only a small amount of each4. Hydroxyl radical – results from ionizing radiation and from incomplete reduction of hydrogen peroxide–The most reactive of the four toxic forms of oxygen–Not a threat to aerobes due to action of catalase and peroxidaseOxygen Requirements•Aerobes – undergo aerobic respiration•Anaerobes – do not use aerobic metabolism•Facultative anaerobes – can maintain life via fermentation or anaerobic respiration or by aerobic respiration•Aerotolerant anaerobes – do not use aerobic metabolism but have some enzymes that detoxify oxygen’s poisonous forms•Microaerophiles – aerobes that require oxygen levels from 2 to 10% and have a limited ability to detoxify hydrogen peroxide and superoxide radicalsOxygen RequirementsNitrogen Requirements•Anabolism often ceases due to insufficient nitrogen needed for proteins and nucleotides•Nitrogen acquired from organic and inorganic nutrients, plus all cells recycle nitrogen from amino acids and nucleotides•The reduction of nitrogen gas to ammonia (nitrogen fixation) by certain bacteria is essential to life on Earth because nitrogen is made available in a usable form•Nitrogen is required for proteins, DNA, RNA, and ATPOther Chemical Requirements•Phosphorus is a component of phospholipid membranes, DNA, RNA, ATP, and some proteins•Sulfur is a component of sulfur-containing amino acids (cysteine and methionine), disulfide bonds critical to tertiary structure of proteins, and in vitamins (thiamin and biotin)•Trace elements – only required in small amounts; usually found in sufficient quantities in tap water (cobalt, copper, manganese, molybdenum, nickel, selenium, silicon, tungsten, vanadium, and zinc)•Growth factors – necessary organic chemicals that cannot be synthesized by certain organisms (vitamins, certain amino acids, purines, pyrimidines, cholesterol, NADH, and heme)Other Chemical RequirementsPhysical Requirements•Adaptation is a complex adjustment in biochemistry or genetics that enables long-term survival and growth•For most microbes, environmental factors fundamentally affect the function of metabolic enzymes•Thus, survival in a changing environment is largely a matter of whether the enzyme systems of microorganisms can adapt to alterations in their