Controlling Microbial ( micro para Flashcards
FACTORS THAT AFFECT
MICROBIAL GROWTH
Availability of Nutrients
Moisture
Temperature
Microorganisms that grow best at high temperatures are
called
thermophiles
Organisms that favor
temperatures above 100°C are referred to as
hyperthermophiles
Most microorganisms prefer a what ph
neutral or slightly
alkaline growth medium (pH 7.0–7.4)
The highest
temperature at which a bacterium has been found living is
around 113°C; it was an archaeon named
Pyrolobus
fumarii.
Microbes that grow best at moderate temperatures are
called
mesophiles
prefer cold temperatures.
Psychrophiles
prefer warm temperatures
but can endure very cold or even freezing
temperatures.
Psychroduric organisms
prefer a pH of >8.5
– Alkaliphiles
prefer a pH of 2 to 5
– Acidophiles
is the movement of a solvent, through a
permeable membrane, from a lower concentration of
solutes (dissolved substances) to a higher
concentration of solutes.
Osmosis
is the pressure that is exerted on a
cell membrane by solutions both inside and outside
the cell
Osmotic pressure
When the concentration of solutes in the external
environment of a cell is greater than that of solutes
inside the cell, the solution in which the cell is
suspended is said to be
hypertonic.
is a condition in which the cell membrane
and cytoplasm of a cell shrink away from the cell
wall; it occurs when bacteria with rigid cell walls are
placed in a hypertonic solution.
Plasmolysis
When the concentration of solutes outside a cell is
less than that of solutes inside a cell, the solution in
which the cell is suspended is said to be
hypotonic.
If a bacterial cell is placed into a hypotonic solution,
it may not burst (because of the rigid cell wall). If it
does burst, the cytoplasm escapes; this process is
known as
plasmoptysis.
A solution is said to be ___ when the
concentration of solutes outside a cell equals the
concentration of solutes inside the cell.
isotonic
Organisms that prefer to live in salty environments
are called
halophilic organisms.
Those that do not
prefer to live in salty environments but are capable
of surviving there (e.g., Staphylococcus aureus) are
called .
haloduric organisms
Microbes that can survive in high atmospheric
pressure (>14.7 psi) are known as
piezophiles.
prefer the same atmosphere that
humans do (~20%–21% O2 and 78%–79% N2, and
<1% other gases)
Obligate aerobes
require reduced concentrations of
oxygen (~5% O2).
Microaerophiles
require increased concentrations of CO2
(5%–10% CO2).
Capnophiles
are killed by the presence of
oxygen
Obligate anaerobes
The time it takes for one cell to become two cells is
called the
generation time
are used in microbiology
laboratories to culture (i.e., grow) bacteria
media (sing., medium)
A ___ defined medium is one in which all
ingredients are known.
chemically
an ___ is a broth or solid containing a rich
supply of special nutrients that promote the growth of
fastidious organisms, for example, chocolate agar
enriched medium
A ___ has added inhibitors that discourage
growth of certain organisms while allowing the growth of
a desired organism, for example, PEA agar.
selective medium
A ___ permits the differentiation of
organisms that grow on the medium, for example,
MacConkey agar
differential medium
is a popular liquid medium in
bacteriology laboratories; it supports the growth of all
categories of bacteria from obligate aerobes to obligate
anaerobes.
Thioglycollate (THIO) broth
Unwanted organisms are referred to as ____;
the growth medium or plate is said to be contaminated
contaminants
After media are inoculated, they must be placed into an
incubator which will maintain the appropriate
atmosphere, temperature, and moisture level; the
process is known as
incubation
Three types of incubators are used in clinical
microbiology laboratories
– A CO2 incubator (contains 5%–10% CO2)
– A non-CO2 incubator (contains room air)
– An anaerobic incubator (the atmosphere is devoid of
oxygen)
A ___ can be used to determine growth
by measuring the turbidity of the medium.
spectrophotometer
are microbes that can
survive and multiply only within living cells (called host
cells).
Obligate intracellular pathogens
A _____ is used to determine the number of
viable bacteria in a liquid sample by making serial
dilutions of the liquid and inoculating onto nutrient agar;
after overnight incubation, the number of colonies is
counted.
viable plate count
are solutions used to disinfect skin and
other living tissues.
Antiseptics
Examples of protozoa that can be cultured in vitro are
amebae, Giardia lamblia, Leishmania spp., Toxoplasma
gondii, Trichomonas vaginalis, and Trypanosoma cruzi
is the destruction or removal of pathogens
from nonliving objects by physical or chemical methods;
pasteurization is an example of a disinfection technique.
Disinfection
is the complete destruction of all microbes,
including cells, spores, and viruses
Sterilization
are chemical substances that eliminate
pathogens on inanimate objects
Disinfectants
The suffix -cide or -cidal refers to
“killing.”
agents kill bacterial endospores
Sporicidal
agents kill fungi, including fungal spores.
Fungicidal
agents kill algae.
Algicidal
agents destroy viruses.
Viricidal
A ___ is a drug or chemical that inhibits
growth and reproduction of microbes
microbistatic agent
A ____ is one that specifically inhibits the
metabolism and reproduction of bacteria.
bacteriostatic agent
is a process that combines dehydration
(drying) and freezing. this process is widely used in
industry to preserve foods, antibiotics, microorganisms,
and other biologic materials.
Lyophilization
refers to the presence of pathogens in blood or
tissues
Sepsis
whereas ___ means the absence of
pathogens.
asepsis
is the prevention of infection.
Antisepsis
The _____ of any species is the
lowest temperature that will kill all of the organisms
in a standardized pure culture within a specified
time
thermal death point (TDP)
A large metal pressure cooker that uses steam under
pressure to completely destroy all microbial life
autoclave
—most microorganisms are not killed, but their
metabolic activities are slowed
Cold
—many dried microorganisms remain viable,
but they cannot reproduce.
Desiccation
used in hospitals and medical and
dental clinics to clean equipment.
Ultrasonic waves
an ultra-violet (UV) lamp is useful for
reducing the number of microbes in the air.
Radiation
used to separate cells/microbes from liquids or
gases.
Filters
—can be altered to inhibit growth.
Gaseous atmosphere
