Bacterial Growth and Metabolism Flashcards
How do bacteria replicate?
Binary Fission
What are prototrophs?
Bacteria that can synthesize all essential metabolites.
What are auxotrophs?
They have acquired mutations that require them to obtain certain essential metabolites from the environment.
What does the growth rate of bacteria depend on?
Availability of nutrients
Environmental pH
Salinity
Temperature
How could a bacteria survive in an acidic pH?
What type of bacteria can pull this off?
H Pylori secretes a urease to convert urea to ammonia and bicarbonate.
What will high salt concentration do to bacterial growth?
Stop it.
How would you classify human pathogens?
Mesophiles because they grow optimally between 30c and 37c
What would you call bacteria that can grow in extreme heat?
Thermophiles
What would you call bacteria that can grow in extreme cold?
Psychrophiles
What is the most important nutrient that impacts the rate of bacterial cell division?
Iron because of its importance for growth and virulence. Hence, the sequestration of free iron in the blood and other fluids is a significant defense against infection.
How do bacteria counter the effects of Iron?
By secreting siderophores which chelate iron and are then actively secreted out of the cell.
How can you measure the bacterial growth in a liquid culture ?
Growing aliquots of the culture on an agar medium.
Measure the turbidity of the liquid culture over time. As the bacteria grow they will cloud the agar which can be quantified using a spectrometer.
In regard to growing aliquots describe the different phases of bacterial growth.
Aliquots are taken at various timesafter broth inoculation.
When is the lag phase of bacterial growth?
Immediately following the inoculation of the liquid culture. During the lag phase essentially no bacteria will grow because they are adapting to their new environment.
Describe the exponential growth phase.
The bacteria have adapted to their new environment and soon begin to establish constant, optimal doubling times during the exponential phase.
**This is a time of maximal DNA and protein synthesis.
When is bacteria most sensitive to antibiotic therapy?
During the exponential “logarithmic” phase.
What are the consequences of the exponential growth phase?
depletion of nutrients and the accumulation of wastes. Which causes the cell division to become equal to the rate of cell death.
What is the phase where cell division is equal to the rate of cell death?
The stationary phase.
When do gram + spore formers initiate sporulation?
During the stationary phase.
How do bacteria respond to antibiotic therapy during the stationary phase?
The cells become refractive to antibiotic therapy
What marks the decline phase?
When cell death exceeds the rate of cell division.
What are planktonic bacteria?
Free-Living bacteria
What is a biofilm?
A protective carbohydrate mix that is adhesive and only formed after a series of events requiring motility and adhesion of planktonic bacteria.
Why are biofilms dangerous?
They are a source of recurrent infections and treatment failures.
How do biofilms interfere with antimicrobial therapy?
- The biofilm ipairs antibiotic access to the residing bacteria.
- It is antiphagocytic
- It is adherent and there is a high risk that it can form on an implant necessitating removal of the device.
What is a disease mentioned in lecture that biofilms a very critical to?
Cystic Fibrosis.
What is the purpose of metabolism?
To provide the energy and building blocks a cell needs to survive and replicate.
How do aerobes and facultative aerobes produce energy in the presence of Oxygen?
In the presence of oxygen pyruvate will be formed and funneled through the Citric Acid Cycle and produce 34 ATP.
What is anaerobic respiration?
Respiration where the organic or inorganic compound serves as the final electron acceptor.
What are the toxic byproducts of aerobic respiration in bacteria?
Hydrogen peroxide and superoxide
Why are strict anaerobes killed in the presence of oxygen?
They do not have Superoxide Dismutase
How do aerobic bacteria circumvent the potentially hazerdous byproducts of aerobic respiration?
They produce: enzymes to diffuse the damage.
Superoxide dismutase
Catalase
Peroxidase
What enzymes do faculative anaerobes produce to combat the hazerdous byproducts of cellular respiration?
Superoxide dismutase
Peroxidase
What do bacteria use folic acid for?
Folic acid is a source of nucleotides and methionine.
What is essential to pathogenesis and the spread of bacteria?
Intracellular survival
What benefit do skin flora provide to their host?
Skin residents inhibit new bacterial growth by producing fatty acids.
How do gut flora provide a benefit to their host ?
Normal Gut flora produce toxins and waste that deter the colonization of harmful bacteria.
How can normal flora harm the host?
- When they spread to a site that is normally sterile.
- They overgrow their niche as a potential pathogen
- Host becomes immunocompromised
What is the term for bacteria in the blood?
Bacteremia
What is pathogenesis?
Any mechanism of disease development
What is Virulance?
A term expressing the degree of pathogenicity
What is colonization?
The presence and multiplication of microorganisms without tissue invasion or damage.
What is infection?
Colonization that generally leads to disease
What is an epidemic?
A disease that rapidly affects many people in a fixed period of time
What is a virulence factor?
Any number of products produced and often secreted by pathogens that allow the pathogen to invade and cause disease in a host and evade host defenses.
