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Chapter 7: Growth Study Guide

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1
Why cultures are important? Physiological Studies
Metabolism, morpholgy, reaction to stimuli
2
Why are cultures important? Genetic Studies
Genome sequencing, knockouts, and mutants to understand gene functions
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Why are cultures important? Taxonomy
Microscopic characters, phylogenetics, culture required for naming
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Why are cultures important? Future Research
Type specimens used for naming new species and making comparisons, preserved strains can be used multiple times
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Phototroph
Organisms that can synthesize all nutrients that the cell needs from a single carbon source
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Auxotroph
Organisms that cannot synthesize all the nutrients they need to grow so they have to pull them from the environment
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Symbiosis
  • Close association of 2 or more microbes
  • Two organisms start living together and depend on one another in order to stay alive
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Alternative culture-free methods: Fluorescent staining (FISH)
Design probes that specifically match a gene region in the organism you're interested in; Able to use microscope to visualize targeted gene regions
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Alternative, culture-free methods: Metagenomics
  • Does not use PCR
  • Uses all DNA available and tries to sequence as much DNA as possible
  • Results in sequences from many different genes across the genome from different species
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Alternative, culture-free methods: Amplicon sequencing
  • Reliant on PCR
  • Targets one gene region that is going to be amplified among samples
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Types of media: Specialized + example(s)
  • Media recipe that is modified to grow something specific for axenic cultures
  • Example: Brilliant green agar, eosin methylene blue agar
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Types of media: Selective + example(s)
  • Designed to grow only certain types of target organisms
  • Example: MacConkey Agar
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Types of media: Differential + example(s)
  • Example: MacConkey Agar, Triple Sugar Ion (TSI) Agar
  • Can distinguish between closely related species by using a color change
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Types of media: Weak + example(s)
Low in nutrients
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Types of media: Rich + example(s)
  • High in nutrients
  • Example: Yeast
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Colony morphology: Bacteria
  • Compact circular
  • Variations in form, texture, elevation, and color
  • Smooth, gelatinous
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Colony morphology: Fungi & Filamentous bacteria
  • Variations in form, texture, elevation, and color
  • Fuzzy
  • Irregular colonies
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Growth curve: Lag Phase
  • Start of experiment a.k.a. inoculation
  • Organism has to change gene regulation to adapt to new environment
  • Only starting with few cells
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Growth curve: Exponential (log) Phase
Rapid expansion in population of cells
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Growth curve: Stationary Phase
Growth rate decreases resulting in nutrients being used up and waste accumulating
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Growth curve: Death Phase
Exponential decline of population
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Chemostat
Continuous culture where nutrients are always being added and waste is removed
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Measuring population growth: CFUs
Live cell counting with serial dilutions
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Measuring population growth: Spectrophotometer
  • Measures how much light passes through broth
  • Low transmittance/high absorbancy of light = too many cells
  • High transmittance/low absorbancy of light = little to no cells
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Measuring population growth: Direct Counts
Use of a microscope slide with counting chamber and grid
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Factors affecting growth: Nutrients
  • Metabolic diversity
  • Growth rate depends on the amount of nutrients in the environment and which nutrients the organisms can use
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Factors affecting growth: pH
  • Some bacteria can alter the pH of their surroundings by producing basic or acidic byproducts
  • Affects macromolecule structures and PMF
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Acideophiles grow at what pH level?
1-6
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Neutrophiles grow at what pH level?
6-8.5
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Alkalophiles grow at what pH level?
8.5-13.5
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Factors affecting growth: Temperature
  • Thermophiles: 55-80ºC
  • Psychrophiles: 10ºC
  • Hyperthermophiles: 80-120ºC
  • Mesophiles (includes OPHs): 10-55ºC
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Factors affecting growth: Osmotic pressure
Osmotic pressure balance is needed to prevent water flowing in and out of cells
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Factors affecting growth: O2, Why is it toxic?
O2 is the only electron acceptor that can be used by respiratory ETS, but byproducts are toxic to the cell
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Factors affecting growth: O2, Different Tolerances (Aerobic)
  • Obligate aerobes: require oxygen, has toxic oxygen defenses
  • Microaerophiles: prefer reduced oxygen levels, has weak toxic oxygen defenses
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Factors affecting growth: O2, Different Tolerances (Anaerobic)
  • Obligate anaerobes: oxygen is toxic, has no toxic oxygen defenses
  • Aerotolerant anaerobes: oxygen isn't toxic but it does not require it either, has toxic oxygen defenses
  • Facultative anaerobes: prefer aerobic respiration but can grow anaerobically, has toxic oxygen defenses
36
Overview of eliminating microbes
  • Heat: denatures proteins and nucleic acids via autoclaving and pasteurization
  • Freezing: candamage cells with ice, used for preservation
  • Radiation: UV 260-280nm wavelengths can damage DNA
  • Chemicals: to kill or inhibit, antiseptics = living tissue, disinfectants = nonliving surfaces
37
What are the macronutrients that are used to make up the macromolecules in a cell?
Carbohydrates, proteins, lipids
38
The enzyme catalase is used to detoxify which harmful oxygen species?
Hydrogen peroxide (H2O2)
39
What is generation time?
The time required for microbial cells to double in number
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