Bacterial Physiology And Metabolism Flashcards
Bacterial physiology and metabolism can be
Bacterial metabolism Growth requirements Bacterial enzymes Bacterial pigments and toxins Bacterial growth curve
Bacterial metabolism definition
Metabolism means the chemical processes that occur within a cell. Bacteria needs energy to grow. Energy is brought through respiration, photosynthesis or fermentation
Respiration definition and pathway
Respiration is an energy yielding process in which oxidation is followed by reduction.
Glucose in the cell - 2 hydrogen atoms gives gluconate
Gluconate + carbon dioxide + 2 hydrogen + Energy gives hydrogen peroxide
Catalase enzyme converts hydrogen peroxide to water and oxygen
In aerobic organisms, the ultimate electron acceptor is ……… because they have ……….
oxygen …………………… peroxidase enzyme
In anaerobic organisms, the ultimate electron acceptor is …… and converted to ……
Nitrate or sulphate ……………………. Nitrite or sulfite
Main elements needed for bacterial nutrition
Carbon and nitrogen
Autotrophs definition and examples
Bacteria can assimilate carbon and nitrogen from simple inorganic sources
Utilize CO2 and ammonium salts
Many saprophytic bacteria
Heterotrophs definition and examples
Require pre-formed sources of nutrition
Glucose and amino acids
Most pathogenic bacteria are examples
Gaseous requirements of bacteria
All bacteria need carbon dioxide to grow. Some depend on oxygen too
According to bacterial need for oxygen, bacteria can be divide to
Obligatory aerobes
Obligatory anaerobes
Aerobe facultative anaerobe
Micro aerophilic
According to the need of carbon dioxide, bacteria can be divided to
- bacteria that grow normally in 0.04% carbon dioxide concentration
- bacteria that need 5-10% carbon dioxide concentration (Capnophilic bacteria)
Capnophilic bacteria examples
Pneumococci
Gonococci
Brucella abortus
Micro aerophilic bacteria definition and examples
Grow best in presence of a trace of O2 (5%) and often prefer high concentration of CO2
Ex: Campylobacter
Aerobe facultative anaerobes definition and examples
Grow well in the presence of O2 and in its absence
Ex: Most pathogenic bacteria like Staphylococcus and E.coli
Obligatory anaerobes definition and examples
Grow only in absence of O2
Ex: Clostridium
Obligatory aerobes definition and examples
Grow only in presence of O2 (21%)
Ex: Mycobacterium tuberculosis and pseudomonas
Moisture effect on bacteria
Drying is dangerous for many bacteria eg gonococci but some bacteria can survive dry places like: T.b Bacillus Spores Clostridium
Optimum temperature for bacterial growth
37 degrees
Optimum pH for bacteria (neutral, acidic and alkaline)
Most pathogenic bacteria can grow at pH of 7.5 with a range of 7.2 to 7.6
Some bacteria prefer acidic media like Lactobacilli
Some bacteria prefer alkaline media like Vibro cholera
Bacterial enzymes definition
Enzymes are biological catalysts which initiate and accelerate chemical reactions without themselves being changed.
Types of bacterial enzymes
Can be:
- Constitutive enzymes
- Inducible enzymes
Constitutive enzymes definition and examples
They are enzymes that are synthesized irrespective of the environmental conditions
Essential for fundamental metabolic pathways and growth of the bacteria
Like respiratory enzymes
Inducible enzymes definition and examples
They are enzymes produced only in the presence of an inducer
Eg proteolytic enzymes
Bacterial pigments types
- endopigment
- exopigment
Endopigments characteristics and examples
Non-diffusible.
Best demonstrated when the organism is grown on the surface of solid media.
Color appears within the colonies
e.g. golden yellow pigment of staph. aureus
Exopigments characteristics and examples
Soluble or diffusible to the surrounding media
Colonies do not change color
e.g. Pseudomonas aeruginosa produce many types of pigments e.g. (pyocyanin and pyoverdin pigments) which turn the medium greenish(-blue).
Factors affecting pigment production
Pigment production is better in aerobic conditions and room temperature
Functions of the pigments
Help in identifying the bacteria
Bacterial toxins definition
They are highly poisonous substances produced by certain bacterial species and lead to tissue damage
Types of bacterial toxins
Endotoxin
Exotoxin
Bacterial growth curve definition and how is it represented graphically
The definitive course of bacterial growth when cultivated in vitro in suitable medium and incubated at suitable temperature
Represented graphically by plotting the log of number of bacteria against the time in hours
Bacterial growth curve phases
Lag phase
Log phase
Stationary phase
Decline phase
Endotoxins properties and examples
DHN FATS
Diffusability: Non-diffuasble Heating: Stable Nature: Lipopolysaccharide produced only by gram -ve bacteria as they have Lipid A Formaline effect: NOt detoxified Antigenicity: Poor Toxicity: Low Specificity: Non-specific, generalised action Examples: Salmonella Typhi
Exotoxin properties and examples
DHN FATS
Diffusability: Diffusable
Heating: Destroyed
Nature: Protein in nature mainly secreted by grame +ve bacteria but can be secreted by Gram -ve
Formaline effect: Converted to toxoid
Antigenicity: Strong
Toxicity: High
Specificity: Selective action
Examples: In gram +ve like: Clostrodium tetani and C.diphtheria
In Gram -ve like: Vibro cholera
Factors affecting the length of the lag phase:
1- The nature of the organism (E.coli has short lag phase while T.B has long lag phase)
2- Size of the inoculum: The bigger, the shorter the phase
3- Stage from which the inoculum was taken: if taken from the log phase, the lag phase will be slow
4- Suitability of the medium: The more suitable the medium the shorter the lag phase
Lag phase corresponds with:
Incubation period of the disease
Log phase corresponds with:
Acute phase of the disease
Stationary phase corresponds with:
Chronic phase of the disease
Decline phase corresponds with:
Convalescent phase ends with complete cure
Sample taken from specimen and grown on a plate?
Culture
Sample taken from a plate to be grown on a second plate?
Sub-culture
