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38 Cards in this Set

  • Front
  • Back
Binary Fission
* DNA replication is linked to doubling of bacterial cell size
* replication is coupled to cell growth and cell division
* division involves the formation of a septum (division plane that develops between 2 cells)
* cell separation
Complex Broth
* contains rich sources of all the nutrients that bacteria need to grow
* many times contains more nutrients than needed to grow
Minimal Medium (Chemically Defined)
* supplies only the essential components for growth
* Carbon source: sucrose or glucose
* Nitrogen source: amino acids
* P, S, K, Mg
* sometimes need cofactors like vitamins
Fastidious Bacteria
* fussy pathogens that often require additional ingredients that are not necessarily found in complex broth

* whole blood, serum
* a bacterial strain that has no unusual nutritional requirements

* WT strain: does not have any additional requirements for growth
* a strain that carries a mutation that confers/causes a nutritional req
* auxotrophs can have a mutation in the gene required for the synthesis of a metabolite
* bacteria that carry these mutations are often less virulent
Number of Bacterial Cells That Will Be Present in Culture at a Particular Time
* N = No * (2 ^ n)

* N = final number of bacterial cells in culture
* No = initial number of bacterial cells
* n = number of generations it has gone through
Calculating Growth Rate / Doubling Time / Generation Time
* Growth Rate = t / n

* t = total time you allow bacteria to grow
* n = number of generations it has gone through
Lag Phase of Bacterial Growth
* do not see much growth or increase in the number of bacteria

* consequence of bacteria adjusting to the growth conditions
Exponential Phase of Bacterial Growth
* exponential growth of bacteria

* growth plotted on linear scale = exponential cruve

* growth plotted on log scale = straight line
Stationary Phase of Bacterial Growth
* number of cells is constant over time

* the cells are still metabolically active, but not as active as log phase
Death Phase of Bacterial Growth
* bacteria are dying because they are running out of nutrients

* some bacteria can sporulate instead of dying: they are metabolically dormant
Turbidity Measurement (Optical Density)
* put the culture in a spectrophotometer
* bacteria scatter light so the amount of light you detect changes
Viable Cell Count
* spread dilutions of a bacterial culture onto plates
* the viable cells will form a colony

* viable cell count goes down faster than turbidity measurement during death phase
Koch's Postulates: Part I
Bacteria should be found in all diseased animals, but not in healthy animals;

False: Tuberculosis patients are infected but do not show symptoms
Koch's Postulates: Part II
Bacteria should be isolated and grown in pure culture (solid media);

Ex. Isolated bacillus anthracis from infected cow and grew them in the juices of the cow's eye
Koch's Postulates: Part III
Bacteria from culture should cause disease in a healthy animal;

False: not all bacteria that cause disease in humans may cause disease in animals
Koch's Postulates: Part IV
Same bacteria should be re-isolated from diseased animals;

False: Intracellular obligate pathogens have not been successfully cultured in complex or minimal media
* optimally grows at low temperatures (less than or equal to 15 degrees Celsius)
* can grow at low temperatures, but optimally grow at higher temperatures
* optimally grow at a temperature close to ours, 15 to 45 degrees Celsius

* Pathogens generally fall into mesophiles
* optimally grow at temperatures greater than 45 degrees Celsius
* grow optimally at low pH

* most acidophiles grow in the environment
* optimally grow at high pH
Acid Tolerant Bacteria
* can grow in acidic conditions but optimally grow in higher pH

* true for most pathogens
Obligate Aerobes
* require the presence of oxygen to respire, produce energy, and grow

* grow at the top of the tube (highest concentration of oxygen)
Facultative Aerobes
* grow best in the presence of oxygen, but do not require oxygen

* can undergo respiration in the absence of oxygen

* grow throughout the tube (any concentration of oxygen)
Microaerobic Bacteria
* require a reduced concentration of oxygen to grow

* grow away from the interface of the air (close to the red indicator)
Obligate Anaerobes
* have very low tolerance for oxygen

* they do not grow in the presence of oxygen

* can only grow in the bottom of the tube (lowest concentration of oxygen)
Aerotolerant Anaerobes
* do not require oxygen, but can tolerate oxygen

* grow throughout the tube
Reactive Oxygen Intermediates (ROI)
* produced by macrophages and lysozymes to kill bacteria;

Ex. superoxide, hydrogen peroxide, hydroxyl radical;

* many bacteria produce enzymes that degrade these ROIs: catalase, peroxidase, superoxide dismutase
* grow at extremely high salt concentrations
Halotolerant Bacteria
* can grow at high salt concentrations, but do not require high salt
* cannot grow at extremely high salt concentrations

* most pathogens fall in this category
* we acquire iron through chelators like transferrin and lactoferrin

* have a high affinity for iron
* bacteria have siderophores that compete with host chelators for iron
* long, thin appendages that occur on the surfaces of bacterial cells

* uses a rotary movement powered by a proton gradient - protons flowing across the membrane generate a turbine

* peritrichous: present over the surface of the bacterium

* polar: present only on one side of the bacterium
Flagellin Structure
* makes up the shaft of the flagellum

* recognized by the innate immune system as a marker for the presence of bacteria