3E - Bacterial Growth Flashcards
Oxygen Requirements - Strict Aerobes
‣ Require O2 for growth
‣ Only a few are pathogens (skin + burn infections)
Oxygen Requirements - Facultative Anaerobes
Use Oxygen if it is available but also have anaerobic methods of energy production
‣ All fungi/most bacteria/ most pathogens
Oxygen Requirements - Microaerophiles
‣ require oxygen for energy production, but are harmed by atmospheric concentrations of oxygen (21% O2)
‣ Campylobacter spp
Oxygen Requirements - Strict Anaerobes
‣ O2 is toxic
‣ Some Pathogens- Clostridium
Macronutrients
‣ Carbon (50% of a typical cell is carbon), H and O
‣ N (12%), P, Mg, Ca, Na, K
Micronutrients
‣ Fe (major role in cell respiration)
‣ +/- growth factors- vitamins, amino acids, purine and pyramidines
Iron (Fe)
‣ Most bacteria require Fe
‣ Fe is bound to proteins in the host
• (Transferrin, lactoferrin)
‣ Pathogens scavenge Fe from host-siderophores
Bacterial growth curve
Lag, log, stationary, death phases
Lag phase - Bacterial growth curve
the cells are not yet dividing and there is no net increase in numbers
‣ Bacteria adapt to the new environment
‣ May take hours to days
Log phase - Bacterial growth curve
or exponential phase the bacteria are dividing at the maximum rate
‣ At this time the bacteria are most sensitive to antibiotics, radiation, etc
Stationary phase - Bacterial growth curve
the growth rate starts to slow down, nutrients are exhausted and toxic wastes accumulate.
‣ Rate of growth = rate of death
‣ Plateau in curve
Death phase - Bacterial growth curve
‣ Death Rate > Growth Rate
Bacteria replicate by
Binary Fission
Generation time
the time it takes for the bacteria to double in number
‣ Doubling time
‣ 20 min to days
‣ Depends on species & environment
Vegitative cells
Bacterial cells that are capable of actively growing
