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.
known as ___, thrive deep
in the ocean and in oil wells, where the atmospheric
pressure is very high.
piezophiles
The media (sing., medium) that are used in microbiology
laboratories to culture bacteria are referred to as
artificial
media or synthetic media,
medium is one in which all the ingredients are
known; this is because the medium was prepared in the
laboratory by adding a certain number of grams of each
of the components
chemically
defined
medium is one in which the exact contents are not known. Complex media contain ground up or digested extracts from animal organs (e.g., hearts, liv-
ers, brains), fish, yeasts, and plants, which provide the necessary nutrients, vitamins, and minerals.
complex media
The time it takes for one
cell to become two cells by binary fission is called the
gen-
eration time.
Bacteria multiply by
binary fission.
is a broth or solid medium containing a rich supply of special nutrients that promotes the
growth of fastidious organisms. It is usually prepared by adding extra nutrients to a
medium called nutrient agar.
enriched medium
is practiced in the
microbiology laboratory
to prevent infection of
individuals and
contamination of the
work environment,
clinical specimens,
and cultures.
Aseptic technique
A bacterial population
growth curve consists
of four phases:
Lag
Log
Stationary
Death
during which the bacteria absorb nutrients, synthesize enzymes, and prepare for cell division.
lag phase
what phase wherethe bacteria multiply so rapidly that the number of organisms doubles with each generation time
Log phase
The bacteria do not increase in number during the
Lag phase
It is during this phase
that the culture is at its greatest population density.
Stationary phase
is used to determine the number of viable bacteria in a liquid sample, such as milk, water, ground food diluted in water, or a broth culture.
viable plate count
describes the
elimination of most or all
pathogens (except bacterial
spores) from nonliving objects.
Disinfection
involves the destruction or elimination of all microbes,
Sterilization
is a drug or chemical that inhibits reproduction of microorganisms, but does not necessarily kill them.
microbiostatic agent
one that specifically inhibits the metabolism and reproduction of bacteria.
bacteriostatic agent
is a process
that combines dehydration (dry-
ing) and freezing.
Lyophilization
the most practical, efficient, and inexpensive method of sterilization of those inanimate objects and materials that
can withstand high tempera-
tures.
Heat
refers to the presence of pathogens in blood or tissues,
sepsis
is the prevention of infection.
antisepsis
any particular species of
microorganism is the lowest temperature that will kill all
the organisms in a standardized pure culture within a
specified period.
thermal death point (TDP)
is the
length of time necessary to sterilize a pure culture at a
specified temperature.
thermal death time (TDT)
an effective means of destroying contaminated disposable materials.
Incineration
is like a large
metal pressure cooker that uses
steam under pressure to completely destroy all microbial
life
autoclave
cleaners consist of tanks filled with liquid solvent (usually water); the short sound waves are then passed through the liquid.
Ultrasonic Waves
Antimicrobial chemical
agents that can safely
be applied to skin
Antiseptics
- It would be necessary to use a tuberculocidal agent
to kill a particular species of:
a. Clostridium.
b. Mycobacterium.
c. Staphylococcus.
d. Streptococcus.
b
Pasteurization is an example of what kind of
technique?
a. antiseptic
b. disinfection
c. sterilization
d. surgical aseptic
b
The combination of freezing and drying is known as:
a. desiccation.
b. lyophilization.
c. pasteurization.
d. tyndallization.
b
Organisms that live in and around hydrothermal
vents at the bottom of the ocean are:
a. acidophilic, psychrophilic, and halophilic.
b. halophilic, alkaliphilic, and psychrophilic.
c. halophilic, psychrophilic, and piezophilic.
d. halophilic, thermophilic, and piezophilic.
d
When placed into a hypertonic solution, a bacterial
cell will:
a. take in more water than it releases.
b. lyse.
c. shrink.
d. swell.
c
To prevent Clostridium infections in a hospital
setting, what kind of disinfectant should be used?
a. fungicidal
b. pseudomonicidal
c. sporicidal
d. tuberculocidal
c
Sterilization can be accomplished by use of:
a. an autoclave.
b. antiseptics.
c. medical aseptic techniques.
d. pasteurization.
a
The goal of medical asepsis is to kill __________,
whereas the goal of surgical asepsis is to kill
__________.
a. all microorganisms . . . . . pathogens
b. bacteria . . . . . bacteria and viruses
c. nonpathogens . . . . . pathogens
d. pathogens . . . . . all microorganisms
d
Which of the following types of culture media is
selective and differential?
a. blood agar
b. MacConkey agar
c. phenylethyl alcohol agar
d. Thayer-Martin agar
b
All the following types of culture media are enriched
and selective except:
a. blood agar.
b. colistin–nalidixic acid agar.
c. phenylethyl alcohol agar.
d. Thayer-Martin agar.
a
