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Microbiology: A human perspective - Chapter 4
How do procaryotic cells divide?
What is generation time?
Time it takes for population to double
What is a pure culture?
Population of cells derived from a single cell - all genetically identical.
How do you obtain a pure culture?
Isolation of cells
What is AGAR?
Gelatinous medium derived from red-algae.
What is the streak plate method?
Most common way of isolating bacteria.
Bacteria streaked on a plate in different directions
What are the growth phases of bacteria?
Lag Phase - preparation for growth.
Log Phase - Period of exponential growth
Stationary Phase - Population growth remains stable; growth = death
Death Phase - Number of viable cells decrease at a constant rate.
Phase of Prolonged Decline - Very gradual decrease in population; may last days or years.
What is a continuous culture?
Bacterial growth can be maintained exponentially.
What are the major conditions that influence bacterial growth?
What 5 categories are procaryotes divided into?
Psychrophiles - freezing temps
Psychrotrophs - cold temps
Mesophiles - comfortable temperatures; disease causing
Thermophiles - hot springs
Hyperthermophiles - hydrothermal vents, volcanoes, usually archae
What does aerobic and anaerobic mean?
aerobic - oxygen
anaerboic - no oxygen
What is an obligate aerobe?
Must have oxygen to grow.
What is an obligate anaerobe?
Can't have oxygen to grow
What is a facultative anaerobe?
Grows better with oxygen.
What is a microaerophile?
Must have very little oxygen to grow.
What is an aerotolerant anaerobe?
Indifferent to oxygen - can grow with or without
What is a heterotroph?
Human - uses organismal carbon as a nutirent source
What is an autotroph?
Plants - uses inorganic carbon
What is a phototroph?
Derives energy from sunlight.
What is a chemotroph?
Derives energy from chemical compounds
What is a complex media?
Contains a variety of ingredients, with no exact formula.
: Nurtient broth, Blood agar, Chocolate agar
What is Differential media?
Allows you to distinguish between different organisms.
What is selective media?
Only allows one selected organisms to grow.
What is a direct cell count?
A direct count of cells usually using a microscope
Doesn't distinguish between living and dead cells.
What is a direct microscopic count?
Counted over a grid
Quickest manual method
What is a viable cell count?
Used to count living cells
What is a plate count?
Measures viable cells growing on solid culture
Based on assumption that one cell gives rise to one colony
Ideal to count between 30 and 300 colonies