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Microbio Lab Reports
Terms in this set (23)
What does a single bacterial colony represent?
a single type of bacteria
What characteristics do we use to identify individual colonies?
organisms which continually colonize the skin surface and provide protection against potentially harmful organisms
organisms that do not continually colonize on the skin surface
What does BSL mean?
Biosafety Levels (ranges from 1-4) which determine the health concerns for microorganisms and provide what type of lab facilities will be required to safely handle it
what is the lawn method?
completing covering surface as if coloring
do not typically cause disease in healthy individuals and present a minimal threat to the environment and lab personnel. May be handled in open and no special containment equipment required
commonly found in community and present a moderate environmental and/or health hazard. associated with human disease of varying severity. may do lab work that is not especially prone to splashes or aerosol generation, using standard microbio practices
Indigenous or exotic microorganisms that cause serious or potentially lethal disease through respiratory transmission. special ventilation systerms are used to prevent aerosol transmission out of the lab, and access to lab is restricted.
great potential for lethal infection. lab is isolated, ventilation and waste under rigid control
Why do we stain bacteria?
increase contrast because like most cells, bacterial cells are transparent. help visualize organism, cell morphology, and different structures like capsules or flagella
the use of a single stain to color a bacterial cell
Stains the background, the bacteria is unstained as it repels the stain
morphology and arrangement are 2 addition elements which aid in the...
identification of bacteria
general shape of bacteria cell
Arrangements of bacteria
single cell, diploid (2 cells), tetrad (4 cells), strepto (chains), or staphy (clusters)
most commonly used staining procedure for bacterial cells and is the essential 1st step for correctly identifying bacteria. istinguishes between two different kinds of bacterial cell walls.
Bacteria that have a thick peptidoglycan cell wall, and no outer membrane. They stain very darkly (purple)
Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma membrane. They stain very lightly (pink). are typically more resistant to antibiotics.
Gram stain procedure
1. Primary stain (Crystal violet- a basic stain)
2. Mordant (iodine)
(something that helps fix dye on or in a cell but does not itself contribute color. forms a crystal violet-iodine complex)
3. decolorizing agent (Ethanol or acetone. critical step which removes stain from gram-negative bacteria producing a clear bacterial cell and will not remove the stain in gram positive bacteria producing a purple cell)
4. Counterstain (Safranin- a basic stain which produces red-pink color in gram negative bacteria)
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