CHAPTER 8 Flashcards
refers to events that occur outside the body,
vitro
refers to events that occur inside the body.)
vivo
factors that affect microbial growth
the availability of nutrients
moisture,
temperature,
pH
osmotic pressure
barometric pressure
composition of the atmosphere.
Cells are composed of
between __% and ___%
water.
70 - 95
There are certain microbial stageshowever, that can survive the complete drying process this is called
dessication
Microorganisms that grow
best at high temperatures are
called
thermophiles
Microbes that grow best at moderate temperatures
are called
mesophiles.
This group includes most of the
species that grow on plants and animals and in warm soil and water.
mesophiles.
prefer cold
temperatures. They thrive in cold ocean water. At high altitudes, algae (often pink) can be seen living on snow.
Psychrophiles
Microorganisms that prefer warmer
temperatures, but can tolerate or endure very cold temperatures and can be preserved in the frozen state, are
known as
psychroduric organisms.
Most
microorganisms prefer a neutral or slightly alkaline
growth medium
(pH 7.0–7.4),
microbes such as those that can live in the stomach and in pickled foods, prefer a pH of 2 to 5.
(acidophiles),
the only
human pathogen that grows well above pH 8.
Vibrio
cholerae
is the pres-
sure that is exerted on a cell membrane by solutions both
inside and outside the cell.
Osmotic pressure
When the concentration of solutes in the environment outside of a cell is greater than the concentration of solutes inside the cell, the solution in which the cell is suspended is said to be
hypertonic.
is defined as the movement of a solvent , through a permeable membrane, from a solution having a lower concentration of solute to a solution hav-
ing a higher concentration of solute.
Osmosis
the loss of water causes the cell to shrink; this shrinkage is called
crenation
Instead, the cell membrane and cytoplasm shrink away from the cell wall. This condition, known as
plasmolysis,
Cells swell up, and
sometimes burst,
when placed into
hypotonic solution.
If sufficient water enters, the cell will
burst (lyse). In the case of erythrocytes, this bursting is called
hemolysis.
cells having rigid cell walls such as plant cells and bacteria. If the pressure becomes so great
that the cell ruptures, the escape of cytoplasm from the cell is referred to as
plasmoptysis.
When the concentration of solutes outside a cell equals the concentration of solutes inside the cell, the so-
lution is said to be
isotonic.
Those microbes that actually prefer salty environments are
called
halophilic,
Organisms that do not prefer to live in salty environments but are capable of surviving
there
haloduric organisms.
