Microbiology Chapter 4
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How do prokaryotes divide?
At what rate do prokaryotic cells divide?
What is Generation Time?
The time it takes for the population to double
What is the growth calculation?
Nt = No x 2^n
What does Nt represent?
number of cells in a population at a time
What does No represent?
The original number of cells in a population
What does 2n represent?
2 to the number of divisions in x time
What is a biofilm?
a community of microbes
Name a beneficial biofilm and a hazardous one
- Beneficial: Waste Treatment Plants
- Hazardous: Dental Plaque
What is a medical issue associated with biofilms?
The can be antibiotic resistant
Name two types of diseases effected by biofilms
- Chronic ear infections
- cystic fibrosis
Why can biofilms be cooperative?
Microbes help one another grow
Why can biofilms be competitive?
Some bacteria make toxic compounds
What is a pure culture?
The growth bacteria of one species only
What is needed for a culture medium?
- Contains nutrients dissolved in water
- may be liquid (broth) or a solid medium
What are the benefits of using agar?
- Not destroyed at high temperatures
- liquifies above 95
- solidifies below 45
- few microbes can degrade it
What is a stock culture?
What are the two systems used to grow bacteria?
What is a closed system?
- A Batch Culture
- Gives characteristic growth curve
- Nutrients are not renewed; wastes are not removed
What is an open system?
- A Continuous culture
- Nutrients are added; wastes are removed
What are the phases of a growth curve?
- Lag Phase
- Log Phase
- Stationary Phase
- Death phase
- Prolonged decline phase
What are the axises on a growth curve?
- X- Time
- Y- Number of cells on a logarithmic scale
What occurs during the lag phase
- cell numbers do not increase
- Cells begin to sythesize enzymes
What occurs during the Exponential (log) phase
- cells divide at a constant rate
- cells are sensitive to antibiotics
- cells produce metabolites
Why are cells susceptible to antibiotics during the Log phase?
Most antibiotics target cells during growth
What is a primary metabolite?
- Created during initial Log phase
- important commercially
What is a secondary metabolite?
- Created during later Log phase
What occurs during the Stationary phase?
- Nutrients are too low to sustain growth
- total number of cells remain constant
What occurs during the Death Phase?
Total number of viable (living) cells decrease at a constant rate
What occurs during the Phase of prolonged decline
- some fraction of bacteria survive
- They've adapted to conditions
What is the difference of growing microbes in a solid medium vs. a broth medium?
- Solid medium: center depleted nutrients more quickly, edge has plenty of O2 and nutrients
- Broth: Nutrients occur evenly throughout medium
What are the 4 major conditions that influence growth?
- Atmosphere (O2)
- Water Availability
What is a psychrophile?
- -5 - 15
- Found in Arctic and Antarctic region
What is a psychrotroph?
- 20 - 30
- Important in food spoilage
What is a Thermophile?
- Common in hot springs
What is hyperthermophile
- Usually archaea
- Found in hydrothermal vents
What do biofilms consist of?
microbes that secrete polysaccharides that other microbes attach to
What is a batch culture
Bacteria grown in a lab where nutrients are not replenished and wastes are not removed
What is a continuous culture?
When bacteria are grown in a lab where nutrients are added and wastes removed
- A cell's place within a solid medium can effect it's survival
- Outer edge- more nutrients
- center- less
How does refrigeration help with bacterial growth?
inhibits mesophiles, but not psychotrophs or psychorphiles
What is an obligate aerobe?
A microbe that cannot grow without O2
What is a Facultative Anaerobe?
A microbe that grows better with O2, but can grow without it
What is a Microaerophile?
- A microbe that requires small amounts of O2
- ex. Helicobacter pylori-causes ulcers
What is an aerotolerant Anaerobe?
- Isn't affected by O2
- ex. Streptococcus pyogen- strep throat
What is a reactive Oxygen Species (ROS)
- Harmful derivates that are formed as by-products of aerobic respiration
- ex. O2- (superoxide) H2O2 (hydrogen peroxide)
What is superoxide dismutase?
Created by aerobic microbes to inactivate O2- and convert it to O2 and H2O2
What is Catalase?
Created by aerobic microbes to convert H2O2 into O2 and H2O
How do aerobic respiration molecules defend against by products?
Creating Superoxide Dismutase and Catalase
What are the 3 different pH tolerant microbes?
- Neutrophiles: pH 5-8
- Acidophile: pH < 5.5
- Alkaliphile: pH >8.5
What is plasmolysis?
When the solute concentration outside the cell is higher, water diffuses out via osmosis. This causes the cytoplasm to shrink away from the cell wall due to dehydration
What are the two types of water availability microbes?
- Halotolerant: tolerate Na concentrations up to 10%
- Halphile: require high levels of Na
- Extreme Halophile: require extremely high levels of Na
What are the Major Elements?
C, O, H, N, S, P, K, Mg, Ca, Fe
What do the major elements do?
Chemical elements that make up cell parts
What are heterotrophs?
Microbes that use Organic Carbon
What are Autotrophs?
Microbes that use inorganic Carbon
What is Carbon Fixation?
Converting inorganic Carbon to Organic Carbon
What is Nitrogen Fixation?
- Conversion of N2 (g) into Ammonia
- Unique to prokaryotes
What are limiting nutrients?
- limits growth because it's the lowest concentration relative to need
- ex. Ph and Fe
What are Trace Elements?
- needed in small amounts
- ex. Cobalt, Zinc, Copper, Molybdenum and manganese
What are growth factors?
Compounds required for growth that the bacteria cannot sythesis itself
What are phototrophs?
Obtain energy from sunlight
What are Chemotrophs?
Obtain energy from chemical compounds
What are Photoautotrophs?
use light and CO2, Carbon Fixation
What are Photoheterotrophs?
Use light and Organic Carbon
What are Chemolithautotrophs?
Use inorganic compounds and CO2
What are Chemoorganoheterotrophs?
Use organic compounds and Organic Compounds
What is a complex Media?
- Contains a variety of ingredients
- highly variable composition
What is a Chemically Defined Media
- composed of exact amounts of chemicals
- used for fastidious compounds
What is selective media?
inhibit growth of species to easier isolate the one being sought
What is differential media?
Contains substances that change the microbes in a recognizable way
What is a single cell multiplied to form a visible mass of cells?
Name 4 reason Agar is useful
- Few microbes degrade agar
- Not destroyed at high temps
- Easy to add nutrients into
- remains solid over the temperature range in which bacteria grow
What occurs after cytoplasm shrinks and the cell dies from osmosis out of the cell?
What is Plasmolysis?
When the cytoplasm shrinks away from the cell way from dehydration
What is Carbon used for in microbes?
a componenet of amino acids, lipids, nucleic acids and sugars
What is a Heterotroph?
uses Organic Carbon
What is an Autotroph?
Uses inorganic carbon
What is Nitrogen used for in cells
to make amino acids and nucleic acids
what is sulfur used for in cells?
Creating some amino acids
What is phosphorous used for in cells?
Creating nucleic acids, membrane lipids and ATP
What are Trace elements needed for?
supporting microbial growth
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