4) Bacterial metabolism, growth and reproduction Flashcards
various biological processes that convert food and other substances into energy and other metabolic byproducts
Metabolism
Biodegradation of large organic molecules into simple molecules
Catabolism
Assimilation of nutrients to form new
and functional units (biosynthesis)
Anabolism
To be able to grow and multiply, every microorganism must have a source of
carbon (to build up their structural and functional molecules)
nitrogen (for vital nitrogenous molecules e.g. amino acids, proteins, DNA, and RNA)
energy (to drive both anabolic - building- or catabolic –degrading- reaction)
In addition to suitable environmental conditions such as;
Temperature,
pH,
Oxygen concentration,
moisture and salt concentrations
A growth environment can be;
Natural: the microorganism’s natural habitat (also called niche)
Artificial: culture media of natural or synthetic component.
catabolic
energy releasin
anabolic:
energy requiring
macronutrients include :
C, N, P, S, K, Ca, Mg, Fe
micronutrients include =
trace elements, growth factors
Bacterial metabolism:
- Glycolysis: 2. Kerb’s cycle: 3. Electron transport chain
Energy Source= Light
Carbon Source= CO2
Nutritional Type ?
Examples?
Photoautotrophs
…….
Cyanobacteria,
some Purple
and Green Bacteria
Energy Source = light
Carbon Source = Organic compounds
Nutritional Type ?
Examples ?
Photoheterotrophs
…
Some Purple and Green Bacteria
Energy Source = Inorganic compounds, e.g. H2, NH3, NO2, H2S
Carbon Source = CO2
Nutritional Type ?
Examples ?
Chemoautotrophs
….
A few Bacteria and many Archaea
Energy Source = Oxidation of organic compounds
Carbon Source = Organic compounds
Nutritional Type ?
Examples ?
Chemoheterotrophs
…..
Most Bacteria, some Archaea
cold-loving organisms able to grow at temp as low as zero °C.
Psychrophiles
psychrophiles that have an optimum temp of 10-20 °C.
Psychrotrophs
organisms with an optimum temp around 37°C.
Mesophiles
organisms with an optimum temp of 45-70 °C
Thermophiles
some archaea with optimum temp of 90 °C and a maximum of 110 °C.
Extreme thermophiles
grow at optimum pH below 7 e.g. (Lactobacillus acidophilus)
(Moulds ) prefer a pH of 5.5 while (yeasts ) prefer a pH of 4.5.
Acidophiles
grow best at neutral pH e.g. most bacteria. .
Neutrophiles
grow best under alkaline conditions e.g. (Streptococcus pneumoniae.)
Alkaliphiles
The pH varies from 0.5 in the ………..
to 10 in the ……….
1) most acidic soil
2) most alkaline lakes
The pH of the human body ranges from 1 (………….) to 8 (……..)
- in the stomach
- in the intestine
Fungi prefer …………..
while bacteria grow well (……..)
- slightly acidic medium
- around neutrality (pH7)
each organism has
-
pH values as described above.
minimum
optimum
maximum
Microorganisms are named according to their response to salt (NaCl) into :
Mild halophiles =
Moderate halophiles=
Extreme halophiles=
require 1-6% salt
require 6-15% salt
require 15-30% salt.
is an organism that grows best at salt concentrations where most microorganisms are inhibited
A true halophile
The term ……….. refer to microorganisms that are able to live in environments with high sugar concentrations
Osmophiles
The concept of lowering water activity in order to prevent microbial growth is the basis for
preservation of foods by drying (using sunlight or evaporation)
Or
by addition of high concentrations of salts or sugars
Reproduction
Cell Division
Binary fission
Vegetative bacterial -> Binary
fission
(=asexual reproduction)
Generation time
time for duplication of bacteria.
•17 min in E. coli
•up to 900 min in Mycobacterium
tuberculosis
Colonies
seen <24H (E. coli) for
up to 3 weeks (M. tuberculosis)
Colonies
Bacterial Growth Curve =
- Lag phase
- Log phase
- Stationary phase
- Death phase
- adapt to new environment
* high biosynthesis
1-Lag phase
- Rapid exponential growth
* Maximum nutrients metabolism
2.Log phase
• caused by depletion nutrients • ↓ metabolic activity and consume non- essential cellular proteins • ↑expression of genes of repair, antioxidant metabolism and nutrient transport
3.Stationary phase
• There is decrease in number (not a growth phase(
- Death phase
a dormant, tough, non-reproductive
structure to resist environmental stress
Spore
Or
spores
Corynebacterium
No spores
Bacillus
Clostridium
Spores
Resistance of spores due to:
- Low water content.
- Low permeability of spore wall.
- Dipicolinic acid + Ca2+.
- Low metabolic activity.
Measurements of bacterial growth :
1- Turbidity
2- Direct microscopic count
3- Standard plate count
The turbidity of a broth culture is determined using a
spectrophotometer
The instrument detects the (............) by a (..............)
amount of light scattered
bacterial suspension of cells.
The amount of light scattered (……….)
is a function of the cell number (…………)
- the optical density
- (the more cells present , the more light is scattered).
A standard curve can be generated (………..) in other situations.
to measure the cell number
Direct microscopic count using =
specially designed slide and
a known sample of the culture.
Turbidity and Direct microscopic count =
Both methods will count both dead and live cells.
gives an indication of cell mass
Dry weight
indication of metabolic activity and therefore cell number
Oxygen uptake
Standard plate count:
Bacterial culture is (diluted )
And
samples of dilutions are placed in (agar plates)
Each cell will undergo multiple rounds of binary fission to =
Then
each cell is called (………)
produce a separate colony on the plate consequently
……….
colony forming unit.
Standard plate count as it measures (………..);
Because this it is another name is (………)
the living cells only (which can divide)
it is known as “Viable count” technique.
