L2: Bacterial products & growth curve Flashcards
What are the characters of bacterial endospores?
- Forming endospores under certain unfavorable conditions as starvation, desiccation, heat, and chemical agents in vitro (outside the body).
- Sporulation occurs outside the body Spore has no metabolic activity & can remain dormant for many years.
What are examples of bacterial endospores?
ο Clostridium (aerobic)
ο Bacillus (anerobic)
What are the types of bacterial endospores?
- According to: ο² Site: -central -subterminal -terminal
ο² Shape: -
rounded
oval
ο² Size:
- bulging
- not bulging
What are the functions of bacterial endospores?
Resting cells, highly resistant to desiccation, heat, and chemical agents.
What is the mechanism of bacterial endospores?
1) The nuclear material in the cell moves to one pole.
2) Cytoplasmic membrane invaginates to form the forespore.
3) Cytoplasmic membrane grows & engulfs forespore within a second membrane.
4) Cortex formation by deposition of Dipicolinic acid and
calcium.
5) Formation of spore coat.
6) Release of endospores.
7) Rest of bacterial cells undergoes autolysis.
Germination of bacterial endospores
- The spore has no metabolic activity and can remain dormant for many years.
- When exposed to water and appropriate nutrients:
β’ Specific enzymes degrade the coat.
β’ Water and nutrients enter.
β’ Germination into a metabolizing, reproducing bacterial cell occurs.
What is the spore structure?
ο Bacterial DNA. ο A small amount of cytoplasm. ο A very little amount of water. ο Cell membrane. ο Peptidoglycan. ο Thick keratin coat with Ca+.
What are the growth requirements of bacteria?
(1) Bacteria nutrition.
(2) Gases.
(3) Moisture.
(4) Temperature.
(5) Hydrogen ion concentration (pH).
(6) Other factorsβ¦
What are bacteria classified into according to nutrition?
- Autotrophic bacteria
- Heterotrophic bacteria
Compare between autotrophic and heterotrophic bacteria
Carbon source
Examples
- Autotrophic (environmental) bacteria:
Inorganic chemicals(CO2). Saprophytic bacteria.
- Heterotrophic bacteria:
Organic sources
Pathogenic bacteria.
What are the nutrients needed by bacteria?
-Basic elements
ο Needed in larger amounts.
ο For structure as basic components.
-Essential metabolites and growth factors
ο Needed in very minute amounts.
ο Used as a catalytic for growth.
What are examples of basic elements needed by the bacteria?
Major:
ο Carbon
ο Nitrogen
οwater
Minor: βΨ³Ψ¨ΩΩ + phosphorusβ
ο Phosphorous ο Calcium ο Sulpher ο Magnesium ο Potassium
What are the examples of essential metabolites and growth factors?
Nucleotides, vitamins
What are bacteria classified into according to the need for oxygen?
- Obligatory aerobes
- Facultative anaerobes
- Obligatory anaerobes
- Microaerophilic
What are obligatory aerobes?
- Grow only in presence of free O2.
Example: TB
What are facultative anaerobes?
- Grow well in the presence or absence of O2.
- They have two systems of respiration.
Examples: pathogenic bacteria.
What are obligatory aneorobic bacteria?
- Grow in absence of O2 and cannot grow in the presence of oxygen (why):
β’ Due to lack of peroxidase enzyme or catalase enzyme so in presence of O2, peroxides will be formed which is very toxic to the organism.
2O2 + 2H ββsuperoxide dismutase ββ> O2 + H2O2
2H2O2 β-Catalaseβ-> 2H2O + O2
Example: Clostridium
What are microaerophilic bacteria?
Grow best in the presence of a minimal amount of oxygen.
Example: Propionibacterium acne.
Is carbon dioxide essential for the growth of bacteria?
Yes
Is the amount of CO2 in the atmosphere sufficient?
β’ The normal atmospheric CO2 content is usually sufficient.
β’ Some organisms require higher concentrations of CO2 (5-10%) to be provided in the culture media for:
- Stimulation of growth (capnophilic) as in Neisseria & Brucella abortus.
- Formation of capsule as in Pasteurella pestis & Bacillus anthrax.
- Enterotoxin production as in Staph aureus.
What is a good amount of the body of bacteria made of?
Water
Is water essential for bacterial cultivation?
Yes
Which type of bacteria needs high conc. Of moisture?
TB
What is the optimum temperature for the growth of bacteria?
37
What is the range of bacteria in which the bacteria can live?
(10-42)
What are psychophilic bacteria?
Growth below the minimum temperature.
What are thermophilic bacteria?
growth above the maximum temperature.
What is the optimum Ph of the pathogenic bacteria?
Most of the pathogenic bacteria grow at optimum pH of 7.5 (neutral).
What are the bacteria that tolerate alkaline media?
alkalophilic bacteria as Vibrio cholera.
What are the bacteria that tolerate acidic media?
acidophilic bacteria as Lactobacillus.
What are other needs for bacteria?
LOM
As:
β’ Light.
β’ Osmotic pressure.
β’ Mechanical factors.
What are the bacterial products?
1) Enzymes
2) Toxins
3) Pigments
4) Other products
What are the enzymes of bacteria?
β’ The enzymes may act on:
ο² Protein β proteolytic enzymes.
ο² CHO β saccharolytic enzymes.
ο² lipids β lipolytic enzymes.
β’ Bacteria also have respiratory enzymes as dehydrogenases and oxidases.
What do enzymes need for their work?
optimum temperature and pH for its action
What are the characters of endopigment bacteria?
ο Remains bound to the body of the organism.
ο Do not diffuse into the surrounding medium.
ο They are demonstrated on solid media.
ο Only colonies are colored.
What are the characters of the exopigment?
ο Diffuses into the surrounding medium.
ο Both colony and medium are colored.
What are examples of endopigment?
ο Red pigment: Serratiamarcescens.
ο Golden yellow: Staphylococcus
aureus.
What are examples of exopigment?
ο Pseudomonas aeruginosa produces:
β’ Blue pigment called pyocyanin.
β’ Yellow pigment called fluorescens
What is the function of endopigment and exopigment?
Play a role in bacterial respiration and also have antibacterial action.
Compare between exo and endo toxins Acc to:
AGD PS ASS EFFECT
ACTION GENE THAT CODES IT DIFFUISBILITY PREPARATION SOURCE ANTIGENICITY AND TOXICITY STRUCTURE SPECIFICITY EFFECT OF HEAT (60-80) EFFECT OF 0.3% formaline
Diffusibility:
ο Diffusible toxins, which diffuse into the surrounding medium.
ο Non-Diffusible toxins, remain bound to the body of the organism and are released only when the organism disintegrates.
Action:
ο On specific organs according to their types.
ο On Interleukin 1 & Tumor necrosis factor.
Antigenicity & toxicity;
ο Highly
ο Less
Gene code it:
ο On plasmid or transferred by Bacteriophage.
ο On chromosome.
Source
ο G + ve mainly & G-ve
ο G β ve
Preparation
ο Growing the organism in fluid media, Then filtrated through a bacterial filter, The filtrate contains the toxin.
ο The disintegration of the organism.
Structure
ο Protein.
ο Lipopolysaccharides
Specificity
ο Specific in action.
ο Nonspecific.
Effect of heat (60-80C)
ο Thermolabile ο Destroyed.
ο Thermostable.
Effect of 0.3%formaline
ο Detoxicated.
ο Not detoxicated.
what are other products of bacteria?οΏΌ
1 Lysin - 1 Cidin - 6 ase
β’ Haemolysin: Produced by many bacteria like Staphylococcus aureus.
β’ Leucocidins: Produced by Staphylococci and Streptococci and kill leucocytes.
β’ Hyaluronidase: Dissolving hyaluronic acid (Cement substances between cells).
β’ Coagulase: Produced by Staphylococcus aureus and causes clotting of plasma.
β’ Protease
β’ DNAse
β’ Staphylokinase: lysis of fibrin
β’ Lipase: the destruction of lipids
How do bacteria reproduce?
β’ Bacteria multiply by simple binary fission which includes:
1) Growth in size (elongation) of the bacterium.
2) Division of the nuclear bodies.
3) Constriction originating from cell wall inwards.
4) Then the bacterium divides into two daughter cells.
β’ Growth on solid media produce:
β’ Colonies that are specific for each bacterial species.
β’ Growth on fluid media may give:
β’ Uniform turbidity (facultative anaerobic bacteria).
β’ Surface pellicle (aerobic bacteria).
β’ Sediment leaving relatively clear medium (anaerobic bacteria).
What is the definition of a growth curve?
Curve demonstrates the relationship between the logarithmic number of living bacteria against the time
What are the procedures done to obtain the growth curve?
Bacteria is cultured on a fluid medium & samples are taken at regular intervals to count the number of living bacteria
Lag phase
ο No multiplication (Constant number).
ο Bacteria increase in size and prepare for reproduction.
ο Correlate with incubation period in vivo.
ο Duration depends on: 1) Nature of organism: E.coliβshort. TBβlong. 2) Type of the media: The more suitable the shorter the lag phase.
3) size of inoculum:
The bigger the shorter the lag phase.
4) Stage from which bacteria is taken:
E.g. If from the logarithmic phase the lag phase will be short.
Logarithmic (exponential) phase
ο The division occurs at a maximum.
ο Correlate with the invasive period in vivo.
ο In this stage, bacteria could be inhibited efficiently by antibiotics.
ο Duration depends on:
β’ Nature of organism.
β’ Type of the media.
Stationary phase
ο The rate of division equals the rate of death
ο The ultimate number of living organisms remains stationary.
ο Correlate with symptoms and signs in vivo.
ο The diminution of the rate of growth due to:
1) Exhaustion of nutrients.
2) O2 Starvation.
3) Accumulation of toxic materials.
Phase of decline
ο The number of the organism begins to decrease. And the rate of death more than the rate of growth.
ο Correlate with convalescent period in vivo.
ο Antibiotics should be continued to completely eradicate bacteria to avoid resistance.
ο β death depends on:
β’ Nature of organism.
β’ Effect of temperature.
β’ Accumulation of toxic metabolites.
