Bmsc 210 Mid1 p7

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Bmsc 210 Mid1 p7
2013-03-10 18:58:17
Bmsc 210 Mid1 p7

Bmsc 210 Mid1 p7
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  1. Growth:
    increase in the number of cells
  2. Binary fission:
    cell division following enlargement of a cell to twice its minimum size (Figure 5.1)
  3. Generation time:
    time required for microbial cells to double in number
  4. Fts (filamentous temperature-sensitive) Proteins (3 components)
    • – Essential for cell division in all prokaryotes– Interact to form the divisome (cell division apparatus)
    • • FtsZ
    • • ZipA
    • • FtsA
  5. FtsZ:
    • forms ring around center of cell
    • -related to tubulin
  6. ZipA:
    anchor that connects FtsZ ring to cytoplasmic membrane
  7. FtsA:
    • helps connect FtsZ ring to membrane and also recruits other divisome proteins
    • – Related to actin
  8. Min Proteins
    • inhibit formation of fts z forcing it into the center of cell
    • MinCD, MinE -occillate back and forth so lowest concentration is in center of cell
  9. MreB
    • -major shape-determining factor in prokaryotes
    • – Forms simple cytoskeleton (spiral-shaped bands) underneath the cytoplasmic membrane in Bacteria and probably Archaea
    • – Localizes synthesis of new peptidoglycan and other cell wall components to specific locations along the cylinder of a rod-shaped cell during growth
  10. Mreb Not found in _____ shaped bacteria
  11. Peptidoglycan Synthesis and Cell Division
    • • Preexisting peptidoglycan needs to be severed to allow newly synthesized peptidoglycan to form
    • – Beginning at the FtsZ ring, small openings in the wall are created by autolysins
    • – New cell wall material is added across the openings
  12. Wall band:
    • junction between new and old peptidoglycan
  13. Bactoprenol
    • carrier molecule that plays major role in insertion of peptidoglycan precursors
    • –is a C55 alcohol (Figure 5.6)
    • – Bonds to NAG and NAM peptidoglycan precursor and carries them across cytoplasmic membrane
  14. Transpeptidation:
    • final step in cell wall synthesis (Figure 5.7b)
    • – Forms the peptide cross-links between muramic acid residues in adjacent glycanchains (removes Ala and uses that energy to form transpeptide bond
    • – Inhibited by -lactam antibiotics: penicillin
  15. Most bacteria have _____ generation times than eukaryotic microbes
  16. Generation time is dependent on growth _____ and ______ conditions
    • medium
    • incubation
  17. Exponential growth
    • • During exponential growth, the increase incell number is initially slow but increases at afaster rate
    • N=  final cell number
    • N=  initial cell number
    • n =number of generations during the period of exponential growth
  18. Generation time (g) of the exponentially growing population
    • t = duration of exponential growth
    • n = number of generations during the period of exponential growth
  19. Batch culture:
    • -a closed-system microbial culture of fixed volume
    • -growth conditions are constantly changing; it is impossible to independently control both growth parameters (growth rate and yield)
  20. four phases of growth curve for population of cells grown in a closed system
    • – Lag phase
    • – Exponential phase
    • – Stationary phase
    • – Death phase
  21. Lag phase
    – Interval between when a culture is inoculatedand when growth begins
  22. Exponential phase
    – Cells in this phase are typically in thehealthiest state
  23. Stationary phase
    • – Growth rate of population is zero
    • – Either an essential nutrient is used up or waste product of the organism accumulates
  24. Death Phase
    – If incubation continues after cells reach stationary phase, the cells will eventually die
  25. Continuous culture:
    an open-system microbialculture of fixed volume
  26. Chemostat:
    • -most common type of continuous culture device
    • – The growth rate is controlled by dilution rate
    • – The growth yield (cell number/ml) is controlled by the concentration of the limiting nutrient
  27. • Dilution rate:
    • -rate at which fresh medium is pumped in and spent medium is pumped out
    • – At too high a dilution rate, the organism iswashed out
    • – At too low a dilution rate, the cells may die fromstarvation
  28. • Concentration
    • -of a limiting nutrient
    • -Increasing concentration of a limiting nutrientresults in greater biomass but same growthrate
  29. Cardinal temperatures:
    the minimum, optimum, and maximum temperatures at which an organism grows (Figure 5.18)
  30. Mesophiles:
    • organisms that have midrange temperature optima; found in
    • – Warm-blooded animals
    • – Terrestrial and aquatic environments
    • – Temperate and tropical latitudes
  31. Extremophiles
    – Organisms that grow under very hot or very cold conditions
  32. Psychrophiles
    •  – Organisms with cold temperature optima
    • – Inhabit permanently cold environments(Figure 5.20)
  33. Psychrotolerant
    •  – Organisms that can grow at 0ºC but have optima of 20ºC to 40ºC
    • – More widely distributed in nature than psychrophiles
  34. Thermophiles:
    organisms with growth temperature optima between 45°C and 80°C
  35. Hyperthermophiles:
    • organisms with optima greater than 80°C
    • – Inhabit hot environments including boiling hot springs and seafloor hydrothermal vents that can have temperatures in excess of 100°C
  36. Other Environmental Factors Affecting Growth (4)
    • • Acidity and Alkalinity
    • • Osmotic Effects on Microbial Growth
    • • Oxygen and Microorganisms
    • • Toxic Forms of Oxygen
  37. Acidity and Alkalinity
    • • The pH of an environment greatly affectsmicrobial growth (Figure 5.24)
    • • Some organisms have evolved to grow best at low or high pH, but most organisms grow best between pH 6 and 8 (neutrophiles)
  38. Osmotic Effects on Microbial Growth
    • • Typically, the cytoplasm has a higher solute concentration than the surroundingenvironment, thus the tendency is for water to move into the cell (positive water balance)
    • • When a cell is in an environment with a higher external solute concentration, water will flow out unless the cell has a mechanism to prevent this
  39. Acidophiles
    bacteria that thrive in acid
  40. Alkaliphiles
    bacteria that thrive in basic substances
  41. Water activity (aw):
    water availability; expressed in physical terms– Defined as ratio of vapor pressure of air in equilibrium with a substance or solution to the vapor pressure of pure water
  42. Halophiles:
    organisms that grow best at reduced water potential; have a specific requirement for NaCl (Figure 5.25)
  43. Extreme halophiles:
    organisms that require high levels (15–30%) of NaCl for growth
  44. Halotolerant:
    organisms that can tolerate some reduction in water activity of environment but generally grow best in the absence of the added solute
  45. Aerobes:
    require oxygen to live
  46. Anaerobes:
    do not require oxygen and may even be killed by exposure
  47. Facultative organisms:
    can metabolize with or without oxygen, use it if it is present
  48. Aerotolerant anaerobes:
    can tolerate oxygen and grow in its presence even though they cannot use it
  49. Microaerophiles:
    can use oxygen only when it is present at levels reduced from that in air
  50. Toxic Forms of Oxygen (4)
    • – Singlet oxygen O2
    • – Superoxide anion  O2-
    • – Hydroxyl radical OH*
    • – Hydrogen peroxide H2O2
  51. Catalase
  52. Peroxidase
  53. Superoxide dismutase
  54. Superoxide dismutase/catalase in combination
  55. superoxide reductase