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Microbiology Lab (BIOL 225): Final Exam
Terms in this set (36)
a visible mass of cells usually resulting from the division of a single cell
Why is the level of contamination measured as number of colonies rather than size of colonies?
because the morphology of individual bacterial colonies that develop in a media usually differ from one species to another (# of unique colonies, not total # or size)
Should one be concerned to find bacteria on the skin? How about molds? Explain.
No, because they are both part of a normal environment.
How can microbial levels be controlled on the skin? On surfaces in the environment? In the air?
Antiseptics for skin
disinfectants for the environment
disinfectants/filters for other types of air
The number of unique colonies on a plate is essentially the number of cultivated species from the environment you tested; this is the measure of microbial biodiversity (or contamination) of a site.
Multiple species can grow as colonies on nutrient media when a plate is exposed to many types of environments (soil, water, fingertips, cell phones, throat), even for just a few seconds.
diversity of microbe contamination
What are the six nutrients all microbes require
Carbon, nitrogen, water, vitamins, minerals, energy
the exact composition and amounts of the individual amino acids, vitamins, growth factors, and other components that make up the medium are not exactly known (do not know components)
a culture medium whose precise chemical composition is known (know components and percentages)
media that is made with components that will allow certain bacteria to grow but will inhibit others from growing
contains substances (indicator dyes OR colorimetric agents) that cause some bacteria to take on an appearance that distinguishes them from other bacteria
Antibiotics, dyes, or Specific inhibitors are often incorporated into media to create selective conditions for growing specific organisms.
What are variables that influence growth?
temp, pH, salt, O2
Luria Bertani (LB) agar is an example of what type of medium?
complex medium, widely used
Autoclaving destroys living cells as well as what other bacterial stage that could cause contamination?
An autoclave is typically used for sterilization of media.
killing or removing any contaminating bacteria
Under what conditions are media typically sterilized in an autoclave?
121°C for minimum of 15 minutes at 15psi
What type of medium components cannot be sterilized in an autoclave?
What is an alternative to autoclaving for sterilizing heat-sensitive materials?
passing a solution through a bacteriological filter of 0.45 microns
Agar is a solidifying agent used in media preparation.
What is the origin of agar?
What makes agar ideal for cultivation of microbes?
it is supportive and is not degraded by most bacteria
Bacteria that derive their carbon from carbon dioxide and their energy from the oxidation of inorganic ions are termed what?
The cyanobacteria use solar energy to fix carbon dioxide. They are classified as
Rhizobium and Azotobacter are examples of nitrogen-fixing soil bacteria that are classified as
Some purple nonsulfur bacteria utilize solar energy but require an organic carbon source. They are classified as
What is commonly used to sterilize special media components that are heat sensitive (i.e. protein additives like growth factors)?
An organism that obtain their carbon source from organic compounds such as polysaccharides, carbohydrates, amino acids, peptides, and proteins.
An organism that derives their carbon requirements from fixing carbon dioxide.
An organism that derives their energy needs from the breakdown of organic molecules by fermentation or respiration.
An organism that oxidizes inorganic ions such as nitrate or iron to obtain energy to fix carbon dioxide
An organism that contain photosynthetic pigments such as chlorophyll or bacteriochlorophyll that convert solar energy into chemical energy by the process of photosynthesis
An organism that derive their energy requirements from photosynthesis, but their carbon needs come from growth on organic molecules such as succinate or glutamate
Aseptic technique ensures...
that no contaminating organisms are introduced into culture materials during handling or inoculation
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