Lecture 9 Flashcards
What does growth refer to?
increase in cell number and NOT an increase in cell size
How does growth work? (4)
1) Cells grow to a critical mass
2) Divide
3) Repeat
4) Growth is exponential 2^n
What factors regulate growth? (3)
1) nutrient availability
2) environmental conditions
3) generation time
What are the chemical requirements for growth? (3)
1) water
2) elements: carbon, hydrogen, oxygen, nitrogen, sulfur, etc
3) organic for heterotrophs: glucose
What are psychrophiles?
microbes that love the cold
What are mesophiles?
microbes that love moderate temperatures
What are thermophiles?
heat loving microbes
What does facultative?
has a range
What is obilgate?
needs a specific condition
What is death above the maximum temp due to?
enzyme inactivation
Which is the most common temperatures for microbes?
mesophiles
At what temperature do most microbes stop growing?
40 F or 5 C
What are obligate aerobes?
require oxygen
What are facultative anaerobes?
use oxygen but can also grow without it
What are obligate anaerobes?
die in the presence of oxygen
What pH do most bacteria grow between?
6.5 pH and 7.5 pH
What is considered an acid? what benefits do acids have?
below 4, can preserve food bc prevents bacterial growth
What are acidophiles?
live at low pH
What are the phases of microbial growth?
1) lag phase
2) log phase
3) stationary phase
4) death phase
What happens in the lag phase?
making new enzymes in response to new medium (aka “LOOK! FOOD!”)