2401 unit 5 Flashcards
optimum growth temperature
the temp where growth rates are the highest
minimum growth temperature
the lowest temp in which the organism can still grow and replicate
max growth temp
the highest temp in which the organism can still grow and replicate
temp for psychrophiles
below 0 to 15
temp for psychrotrophs
4 - 25
temp for mesophiles
20 - 45
temp for thermophiles
50 - 80
temp for hyperthermophiles
80 - 100
optimal pH for acidophile
less than 5.5
optimal pH for neutrophile
~ 7
optimal pH for alkaliphile
8 - 11.5
hypotonic environments
lower concentration of solutes in the environment than the cell
hypertonic environments
higher concentration of solutes in the environment than the cell
for hypotonic, the movement of water into cell leads to
lysis
for hypertonic, the movement of water out of the cell leads to
crenation
microbes with cell wall are susceptible only to
hypertonic
hypotonic for cell wall microbes
water still moves into the cell; presence of the cell wall prevents lysis
hypertonic for cell wall microbes
movement of water out of the cell eventually leads to plasmolysis (separation of the plasma membrane from the cell wall)
halophiles
organisms that require salt for growth
halotolerants
organisms that do not need salt for growth but can survive and grow in the presence of high salt environments
macronutrients are
elements needed in large amounts = carbon, hydrogen, oxygen, phosphorus, sulfur and nitrogen
micronutrients are
elements needed in small amounts = sodium, potassium, calcium, iron
organic growth factors are
molecules such as vitamins, essential amino acids
reactive oxygen species
aerobic cellular respiration or exposure to atmospheric oxygen leads to the formation
examples of ROS
hydrogen peroxide, superoxide, hydroxyl radicals
superoxide dismutase
breaks down superoxide anions to produce hydrogen peroxide
peroxidase
breaks down hydrogen peroxide to produce water; requires use of NADH
catalase
breaks down hydrogen peroxide to produce water and oxygen; does not require use of NADH
catalase test is done where
hydrogen peroxide is added to a smear of bacteria on glass slide
positive catalase test
bubbling, bacteria has catalase
negative catalase test
no bubbling, bacteria does not have catalase
biofilms are
complex dynamic communities of bacteria (highly structured, and are there to provide selective advantage for members)
formation of biofilms
- reversible attachment of planktonic cells
- first colonizers become irreversibly attachment
- growth and cell division
- production of EPS and formation of water channels
- attachment of secondary colonizers and dispersion of microbes to new sites
problems with biofilms
medical devices (catheters) are suitable for biofilm formation, which can lead to deeper infections
hard to remove and difficult to treat with antibiotics and antimicrobial agents
liquid media
broth cultures where cells are in suspension (grow large amounts)
solid media
made by using agar (used to isolate for characterization)
why agar is used in culturing
complex polysaccharide that is used as solidifying agent & not metabolized by many microbes
chemically-defined media
used to grow microorganism where the specific requirements are known
complex media
mixture of extracts and digesrs from yeasts, meats, or plants; used to grow a variety of microorganisms, or when sample identity is unknown
selective media
a chemical has been added that allows for the growth for some microbes but prevents the growth of others
differential media
a chemical has been added that allows identification of microbes based on their growth, colour or appearance on medium
mannitol portion is differential because
we can visually see a pH change which indicates that fermentation has occurred
salt portion is selective because
it only allows halophiles/halotolerants to grow
blood agar is
differential media because it shows which colonies are capable of hemolysis
beta-hemolysis
alpha-hemolysis
gamma-hemolysis
complete clearing
partial clearing
no clearing
after one round of binary fission
the # of bacteria has doubled
generation time is
the time it takes for a bacterial population to double
lag phase
cell synthesizing new components either to replenish materials or adapt to new medium (# of cells changes very little because cells do not usually immediately reproduce in new medium)
log/exponential phase
cellular reproduction is most active and generation time reaches a constant minimum
stationary phase
growth rate slows and the number of microbial death balances the number of new cells (nutrients are being depleted while wastes accumulate)
death phase
number of deaths increases and exceeds the number of new cells formed
microscopic count is
using a microscope, a special slide is used that contains a grid and carries a known volume of sample, number of cells is then counted
advantages of microscopic count
numbers can be achieved right away & method can be used for samples that do not grow well in labs
disadvantages of microscopic count
overestimation in numbers as dead cells and debris can be counted as a cell; also cells that are moving may be counted multiple times
turbidity
an indirect method where cells are counted by measuring the amount of turbidity (cloudiness)
disadvantages of turbidity
standard curves are need as each species may scatter light differently
overestimation of bacterial numbers as dead cells and debris can be counted as a cells
viable counts
the idea is to spread out the bacteria sufficiently so that each individual cell will result in a visible colony
of colonies = # of bacteria in the original sample
viable counts measured in
colony-forming units
goal to achieve a dilution to obtain a countable plate is
20-200 colonies
steps for bacterial abundance in a sample
- calculate the bacterial concentration of usable dilution -> CFU/amount plated = CFU/mL
- calculate final dilution factor
= total volume in tube/amount transferred (multiple all tubes together) - calculate bacterial concentration of original sample
bacterial concentration of the usable dilution X final dilution factor
