True or false: Most bacterial pathogens can grow in the presence AND absence of oxygen.
How do bacteria replicate?
Binary fission: 1 cell divides to yield 2 daughter cells. Those 2 daughter cells divides to produce 4 cells, etc.
1 Disrupt cell wall 2 Replicate bacterial genome & segregate to daughter cells 4 Establish new ends (septa) to cytoplasmic (& outer) membrane
Growth rate of an organism depends on 4 factors. What are they?
Availability of nutrients, Environmental pH, Salinity, Temperature
What are prototrophs?
Bacteria that can synthesize all essential metabolites
What are auxotrophs?
Bacteria w/ acquired mutations that require them to obtain certain essential metabolites from environment
Name 2 common inhibitors of bacterial growth
Acid ph, High salt
Name 1 bacterium resistant to acid pH. How does it overcome acid environments? What is the consequence?
Secretes urease, which converts urea to NH3 & HCO3 to establish infection in gastric tract to cause ulcers
Human pathogens grow optimally at what temperature? This makes them fit which classification?
Between 30C-37C Mesophiles
Bacteria that can grow in extreme cold are called...
Bacteria that can grow in extreme heat are called...
thermophiles Can be source of important heat resistant enzymes (i.e. DNA polymerase used for PCR)
Iron is a particularly important nutrient w/ regard to bacterial growth & virulence. Why?
Sequestration of free iron in blood & other body fluids is a significant defense against infection
What proteins are used to bind & sequester iron?
Transferrin & lactoferrin
How do bacteria counter iron limitation?
Secrete siderophores that chelate iron and are then actively transported to bacterial cell
Describe 2 laboratory methods that can be used to measure bacteria in culture
1 Grow aliquots of the culture on agar medium as aliquots are taken at various times after broth inoculation 2 Measure turbidity of liquid culture over time: As bacteria multiply, they cloud the broth which can be visibly seen & measured using spectrophotometer
Describe the stages of bacterial growth in culture
1 Lag phase: Essentially no growth occurs. Bacteria are adapting to environment & reprogramming gene expression to meet new needs 2 Exponential phase: Bacteria begin to replicate and establish constant, optimal doubling times 3 Stationary phase: No net increase in # of viable cells. Consequence of cell growth is depletion of nutrients & accumulation of waste. Metabolism greatly reduced such that rate of cell division = rate of cell death 4 Decline: As nutrients deplete and waste increases, rate of cell death > rate of cell division
During which growth phase do bacteria experience maximal DNA protein synthesis and are most acutely sensitive to antibiotic therapy?
During which growth phase is it best to gram stain?
During which growth phase do bacteria become somewhat refractive to antibiotic therapy?
During which growth phase do Gram positive spore formers initiate sporulation?
Individual, free-living backteria are called...
What is a biofilm?
Encase bacteria in protective carbohydrate matrix that's adhesive and formed after series of events requiring motility and adhesion of planktonic bacteria
Why are biofilms a problem?
-80% of infections result from organization of bacteria in biofilm -Source of recurrent infections & treatment failures -Impairs antibiotic access to bacteria -Anti-phagocytic -Often requires removal of infected implanted valve due to its adherent nature