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Gram Stain Picture

metachromic granules: Methylene Blue Stain Picture

Methylene Blue Stain

Corynebacterium diptheriae-microscope-looked blue-thin blue line with dot on the end-tiny blue dots are phosphate granules (metachromic granules)-stores phosphate within the cell-blue dots are inside the actual rod

Capsule Stain Picture


Klebsiella pneumonia-microscope-looked purple with white-small thin oval shaped with little line in the middle-capsule
Examples of organisms that produce capsules:
Enterobacter aerogenes, some Streptococci, and Klebsiella pneumonia
Capsule stain : some organisms produce capsules on the outer surface of the cell
-organisms with capsules are usually more infectious and cause more severe infections than those that do not contain them
-capsules will appear as a clear area around the bacterium, and the organism will appear red or pink
-capsules are easily destroyed by water and heat, so do not heat fix or add water to slides

Negative Bacillus Picture

Negative Bacillus Desc

Bacillus cereus : rods (still had four little segments in rods)-microscope
stain provides dark background so organisms appear white/clear
-the stain allows visualization of shape, size, and arrangement

Negative Stain Micrococcus Picture

Negative Stain Micrococcus Desc

Micrococcus luteus : dark background, usually pairs or tetrads (lots of pairs ; pointer was on tetrads)-microscope
Negative stain: stain provides dark background so organisms appear white/clear
-the stain allows visualization of shape, size, and arrangement

Negative Stain: Streptococcus Picture

Negative Stain: Streptococcus Desc

Streptococcus sp. (pneumonia)-pairs or chains-pointer was on chains of four-microscope

Acid Fast Picture

Acid Fast Desc

Mycobacterium sp (leprae or tuberculosis)-not sure which one but this is a microscope one
-organisms contain a thick peptidoglycan layer like gram positive organisms
-organisms also contain mycolic acid surrounding the peptidoglycan layer on the outside of the cell
-mycolic acid is very impervious to most stains
-carbolfuschsin binds very strongly to the mycolic acid, even when it is washed with acid alcohol
-if your slide is all pink on a control slide, you either did not rinse the carbolfuchsin off, or you did not add the methylene blue
--acid fast organisms stain pink
-non acid fast organisms are blue
-if your slide is all blue even when you used both control organisms you most likely rinsed with too much alcohol
-if your slide is all pink on a control slide, you either did not rinse the carbolfuchsin off, or you did not add the methylene blue
Organisms that are considered to be acid fast:
Mycobacterium tuberculosis (TB)
Mycobacterium leprae (leprosy)
Nocardia asteroids (a filamentous bacterium (actinomycete) that causes lung and skin infections)

Endospores Picture

Endospores Desc

Bacillus (cereus)-microscope?
Clostridium (botulinum)-microscope?

Spore stain:
-spores appear green and organisms will stain pink
-spores are very resistant to heat, dessication (drying) and radiation
-bacteria produce endospores in unfavorable environments so they can propagate when a favorable environment returns
-many anaerobes produce these so they can survive in an environment containing oxygen. When an anaerobic environment returns they will begin reproducing
-spores are resistant to staining so must use heat with the stain so it will bind
-on a control slide, if you have all green, be sure to rinse all the malachite green off (you should not have any slide that is all green)
-on a control slide, if you have all pink, you did not heat the malachite green enough (***for control slides only!!!! organisms that do not produce spores will give this type of result)

Organisms that produce spores:

Bacillus subtilis
Bacillus cereus
Clostridium botulinum
Clostridium sporogenes

Spores can be located in three different parts

Central: Bacillus
Subterminal: Bacillus
Terminal: Clostridium (tetanus)

Amphitrichous Picture

Amphitrichous: Spirillum volutans-microscope

Peritrichous Picture

Peritrichous: Proteus vulgaris-microscope

Simple stains:

-a staining technique which uses only one stain, which is rinsed off with water
-you determine cell size, shape, arrangement, and whether organisms are present by using one of these stains
-dyes commonly used for simple stains include crystal violet, carbol fuchsin, and safranin

Gram stain: explanation of steps

1)crystal violet: penetrates the peptidoglycan layer of gram positive organisms, binds to outside of both gram posistive and gram negative organisms
2)iodine: complexes with the crystal violet both within the peptidoglycan layer and the cell surface
2) alcohol-acts as a decolorizer- washes crystal violet from cell surface, shrinks peptidoglycan layer
-You can wash all of the crystal violet away
-the stain often runs onto the back of slides so rinse the back of the slide with water so you do not overdecolorize
4) Safranin: a counterstain, binds to negatively charged cell surfaces, which includes both gram positive and gram negative cells
Positive: purple
Negative: pink

Gram positive organisms:

Staphylococcus aureus
Lactobacillus acidophilus
Bacillus subtilis
Enterococcus faecalis
Sporosacrcina ureae
*Yeasts are also gram positive:
Saccharomyces cerevisiae
Candida albicans

Gram variable

Corynebacterium diphtheria (they are also pleomorphic-different forms)

bacterium Shape and Arrangement

-Each bacterium will have it's own shape, such as coccus, bacillus, coccobacillus, spirochete or sprillum.
-Stains will allow you to see the shape of cells. Sometimes, the names will also tell you the shape, but not always.
-Bacteria may or may not exhibit a particular arrangement when the cells do not completely separate from each other. Most bacteria do not have an arrangement.

Examples that have an arrangement:

Mircrococcus: tetrads
Sarcina: sarcinal (3d two sets of four)
Streptococcus: pairs or arrangement
Neisseria: diplococcic
Staphylococcus: grape-like clusters
Mycobacterium: cords
Corynebacterium diptheriae (pleomorphic): Chinese letters

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