Microbial Growth and Nutrition Flashcards
How do we define bacterial growth?
Orderly increase in numbers
What are the B,C,D periods of binary fission?
B: Cell increases in mass and size
C: DNA replicates and the 2 strands separate
D: Synthesis of a septum forms 2 identical cells
Do all cells replicate at the same rate?
No, depending on the species they all have an optimal replication rate
What is the regeneration time of E. coli?
15 mins
How do bacterial and archaea cells reproduce?
Asexually
-generation time is the interval between successive binary fissions
What are the 4 phases of the microbial growth process?
- Lag phase
- Logarithmic phase
- Stationary phase
- Decline phase
What happens during the lag phase?
No cell division occurs while bacteria adapt to their new environment
What happens during the logarithmic phase?
Exponential growth of the population occurs, human disease symptoms usually develop
What happens during the stationary phase?
When reproductive and death rates are equalized
What happens in the decline phase?
Accumulation of waste products and decline of resources causes the population to die
What state can bacteria exist in and why?
Metabolically inactive states which can be a response to potential or actual environmental change
Why are endospores important for cell growth?
They are a response to nutrient limitations
-have thick walls to survive harsh conditions
What is a psychophile?
Can grown between -10 and 20
What is a psychotrops?
Can grow between 0-30
What is a mesotroph?
Can grow between 10-58
What is a thermophile?
Can grow between 40-73
What is a hyperthrermophile?
Can grow between 76- 110
What are obligate aerobes?
They require O2 to grow
What is a microaerophile?
Live in low O2 environments
What are facultative anaerobes?
Grow either with O2 or in reduced O2 environments
What is a capnophilic bacteria (microaerophils)?
Require an atmosphere low in O2 and rich in CO2
At what pH do majority of species grow at?
~7.0
What are barophiles?
Withstand really high hydrostatic pressure
What is media?
What ever we make to grow bacteria on
-most require special growth factors or nutrients
What is agar?
Complex polysaccharide from cell walls of red algae
Why do we use agar as a medium?
- Most microbes can not digest it
- Dissolves in water at 100
- Solidifies below 40
- can culture hyperthermophiles
In a test tube with agar, why do you slant it?
Gives more area for you to put bacteria on the grow
What is nutrient broth?
Powdered beef extract
- AA mix from digested proteins
- 1.5% agar if you need to solidify
What us a defined media?
Synthetic media for something specific you want to grow
-exact chemical composition is known
What are culture media used for?
growing microbes and to measure their growth
What are the 2 basic types of culture media?
Complex medium is chemically undefined or complex medium such as nutrient broth or nutrient agar
What is a complex media
?
Contains nutrients released from partial hydrolysis of yeast, beef, soy or proteins
- chemical comp is not known
- can support wide variety of microbes
What does a a selective medium contain?
Ingredients to inhibit growth of certain species and allow the broth of others
What are differential mediums?
Differential medium contains specific chemicals to indicate species that possess or lack a biochemical process
What are fastidious organisms?
Require an enriched medium containing specific nutrients
What is a selective media?
Contains substances that either favour or inhibit certain microbes from growing
How do you measure population?
Measurements are made using pure cultures
What is a pure culture?
Population consisting of only one species of prokaryotes
What are the 2 forms of isolation?
Pour-plate: allows separation of species through dilution of sample
Streak-plate: Spreads individual cells to form discrete colonies of species
How do you measure population growth?
Turbidity: cloudiness with spectrophotometer
Microscopic count: Count bacteria in the squares
Visually: Counting them
