R1 - Microbial growth Lectures Ch. 6 & 5 , Bacterial Diseases of the Respiratory system, Biofilms (ch.4 & 6) Flashcards
Generation Time
The time it takes for one cell to 2 into two cell wall.
Equation for calculating number of bacteria
N = No2^n
Terms for the growth curve/logarithmic growth in order.
- Lag phase
- log/exponential phase
- Stationary phase
- Death phase
Lag Phase
Cells do not immediately reproduce in new medium. So the number of cell changes very little. Microbial population undergoes a period of intense metabolic activity involving synthesis of enzymes and various molecules to start growth.
Log / exponential phase
Cells begin to divide and enter period of growth/logarithmic increase. Cell reproduction is most active by being metabolically active because bacteria cells need to be produced. Binary fission.
Binary fission
prokaryotic cell preproduction by division into two daughter cells.
Stationary phase
Growth rate slow’s, the # of microbial deaths balance number of new cells and population stabilizes. Stabilizes because exhaustion of nutrients and accumulation of waste products and harmful changes in pH play a role.
Death Phase
Number of deaths exceed number of new cells formed.
Direct Methods definition
get an exact cell number
List Direct Methods
- Direct microscopic count,
2. standard plate count
Indirect Methods definition
get a relative number of cels (not exact count)
List of indirect methods
- turbidity
2. dry weight or mass
Direct microscopic count
Direct Measurement.
A measurement volume of a bacterial suspension is placed within a defined area on a microscope. Counting cell under marked square centimeter of slide.
Turbidity
Indirect Method
Fast.
Use spectrophometer, instrument used to measure turbidity (the cloudiness of a suspension)
measures light absorbance of test tube with bacteria
measurements are in O.D. (optical density)
Measurements count live cells and dead cells.
Dry Weight Mass
Indirect method
Fast.
Takes bacteria from growth medium, filters to remove extraneous material, and dried in a desiccator. It is then weighed.
Also measures dead and living cells.
Standard Plate count
Direct Method
1.A series of dilutions of growing bacteria.
Dilutions of 1ml from previous tube is added to 9ml of broth.
2.Grow bacteria on media in petri plates
3.count colonies and calculate cfu/ml
method counts only viable cells
Advantages and Disadvantages of Standard Plate count
Advantages:
Counts only viable cells
can be correlated with turbidity measurement
Disadvantages:
slow
overnight process
Advantages and disadvantages of Direct microscopic count
Advantage:
Quick
Disadvantage:
counts dead cells as well as viable cells
Viable - alive , able to reproduce
What is Binomial Nomenclature?
the system of having two names (genus and specific ) for each organism
e.g. Staphylococcus Aureus (should be italicized or underlined)
Lysosome
Contains Digestive Enzymes that break down various molecules and (some) bacteria
Advantages and disadvantages of Turbidity
Advantages:
Fast
Can correlate to standard plate count but is faster than that.
Disadvantages:
measures viable and dead cells (still absorb light)
Advantages and Disadvantages of Dry Weight or mass
Advantages:
Fast
good for organisms that are clumped together
Disadvantages:
measure living and dead cells
Organisms that obtain carbon source are called?
Autotroph
Heterotroph
Autotroph
Uses inorganic source of carbon such as CO2 e.g.plants
Chemotroph
gets energy from chemicals
- chemolithotroph - chemoorganotroph
Organisms that obtain Energy source are called?
Phototroph
Chemotroph
Phototroph
Light as primary energy source
e.g, plants
Heterotroph
uses an organic source of carbon such as glucose (C6H12O6)
e.g. animals
Chemolithotroph
Chemotroph
- gets electrons and energy from inorganic compounds
e. g. some prokaryotes
Chemoorganotroph
Chemotroph
gets electrons and energy from organic compounds. e.g. animals
Aerobe
Microbes that use molecular oxygen