Micro Lab Practical 2 Flashcards
Define diplococcus
When cocci shaped cells divide and remains attached after division is complete.- Same applies for diplobacilli.
What types of cell shapes are associated with a single cell arrangement?
Cocci, bacilli, spirilla, spirochetes, and vibrios
What cell shapes are associated with chain arrangements?
Cocci and bacilli
What cell shapes are associated with tetrodes, cubes (sarina), and cluster (staphylo-) arrangements?
Cocci
What cell shapes are associated with palisade and angular arrangements?
Bacilli
Describe a tetrad
When a second cell division occurs in a plane that is perpendicular to the first division. ( looks like a square made of four circles)
Describe a cube (sarina) shape arrangement
When a third cell division occurs that is perpendicular to the first two produces a cube shaped arrangement of eight cells. (cube made of eight circles)
Describe staphylococcus
When the division plane of a coccus are irregular, a cluster of cells is produced.
When are cellular arrangements easiest to see?
When the organisms are grown in broth, or observed from a direct smear.
What are stains made of?
Solvent (water or ethanol) and a colored molecule (often benzene derivative) called chromogen.
Define chromophore
The portion of a chromogen that gives it color. Chromogen may have multiple chromophores, each adding intensity to the color.
Define auxochrome
The charged portion of the chromogen and allow it to act asa dye through ionic or covenant bonds between the chromogen and the cell.
Define basic stains
When autochrome becomes positively charged as a result of picking up a hydrogen ion or losing a hydroxide ion- are attracted to negative charges on the surface of most bacterial cells.
What are common basic stains?
Methylene blue, crystal violet, and safranin.
What are basic stains used on?
bacterial smears that have been heat fixed.
What does heat fixing do to bacteria?
Kills them, makes them adhere to the slide, and coagulates cytoplasmic proteins to make them more visible. Some cellular distortion is caused.
Which cells are decolorized by the deodorizer in gram staining?
Gram negative.
What is the primary stain in gram staining?
Chrystal violet
What is the mordant in gram staining?
Iodine- used to enhance the crystal violet staining by forming a crystal violet-iodine complex.
What is the counterstain in gram staining?
Safranin- which will stain the gram negative cells.
How are gram negative cell walls different than gram positive cell walls?
Gram negative have higher lipid contentment and thinner peptidoglycan layer.
What are capsules composed of ?
Mucoid polysaccharides of polypeptides that repel most stains because of their neutral charge.
What are acid stains?
Congo red or nigrosin- used for staining the background while doing a capsule stain.
What kind of stain is used to stain cells in the capsule staining process?
Basic stains
