Exam 1 - Ch. 6 - Microbial Growth Flashcards
When speaking of reproductive activities of microbes, what does the term “growth” refer to?
An increase in the size of a population.
What is an aggregation of cells arising from a single parent cell called?
colony
What is a collection of microbes in a complex community called?
biofilm
What is the difference between a colony and biofilm?
A colony is microbes of the same origin (all same microbes) and a biofilm is all different microbes.
Carbon sources from CO2 is classified as what by type of growth?
autotroph
Carbon source from the environment/organic compounds is classified as what by type of growth?
heterotroph
If the energy source is from light what are they classified as by type of growth?
photoautotrophs or photoheterotrophs
If the energy source is from chemical compounds what are they classified as? by type of growth?
chemoautotrophs or
chemoheterotrophs
What would animals be classified as by type of growth?
chemoheterotrophs
What would bacteria be classified as by type of growth?
Varies -
photoautotrophs
Chemoautotrophs
photoheterotrophs
What are the 7 growth requirements for microbes?
Oxygen Temperature pH Moisture Osmotic pressure Light Food
As a rule, what is the most important factor affecting the growth of microorganisms?
temperature
Why isn’t oxygen as important for the growth of microbes?
Microorganisms vary widely in their oxygen requirements. anaerobe vs. aerobe
What are the three organism classifications according to temperature?
psychrophilic
mesophilic
(hyper)thermophilic
Which temperature does psychrophilic like?
Prefers cold temperatures.
What type of temperature does mesophilic prefer?
Prefer moderate temperatures (usually about normal human body temperature)
What type of temperature does (hyper) thermophilic prefer?
Prefers high temperatures
Most pathogenic organisms are classified under what according to temperature?
mesophilic
What pH range do most microorganisms thrive?
pH 6-9
What pH do most animal pathogens work best?
pH 7
What is “pickling” food?
Preserving food in an acidic medium (like vinegar)
Why is moisture important in cell growth and maintence?
Food and waste transported via H20 through cell wall and water is a necessary building material in cell synthesis.
What are the moisture requirements for microbes?
Varies widely (ex: salt vs. fresh water organisms)
Which cells will be at rish for bursting under osmotic pressure
Animals and mycoplasma (cells without cell wall)
Which color pigmented bacteria use light as a source of part or all of their energy?
Green and purple
However, what happens to most pathogens under direct sunlight?
They are killed.
Two different types of culture media.
Selective media
Differential media
Type of media that contain substances that favor or inhibit the growth of particular organisms.
Selective media
Type of media where the presence of visible changes in medium or differences in the appearance of colonies help differentiate organisms.
Differential media
When the exact composition is known what kind of media is this?
Defined (synthetic) media
When the exact chemical composition is unknown what is this media called?
Complex media
Most common type of complex media?
blood
What is an example of selective media?
sabouraud dextrose agar
What is an example of differential media?
Blood agar
What is an example of media that supports both selective and differential?
MacConkey agar
Sabouraud dextrose selects for what and inhibits what?
Selects - fungus (esp. Yeast)
Inhibits - bacteria
