Lab Practical 2

Negative stain

Procedure results in colorless bacteria against a stained background

Negative stain

Background dark to see colorless organisms, technique viewing microbes difficult to stain

Spirochetes

Spiral shaped cells, negative stain only, corkscrew shaped

Nigrosine

Used in negative statin procedure as solution

Negative stain

Air dry only to preserve cell’s natural state

Simple stain

Unstained bacteria are difficult to see because they are generally clear and hard to distinguish from background

Simple stain

Visibility of shape, size, and arrangement. Most bacterial cells slightly negative charge to combine with positive charged basic dyes

Simple stain

Must heat fix after air dry to remove excess water so organisms do not rinse off during staining

Crystal violet

Positive; dissolves in ETOH; purple

Methylene blue

Dissolve in alcohol; blue

Carbol fuchsin

Dissolve in alcohol; fushia

Safranin

Dissolve in ETOH; Negative; pink

Malachite Green

Dissolve in H2O

Simple stain

One positive basic stain used, not differential because only one identified

Coccus

Spherical cells in single; 2 divide remain in pairs called diplococcus

Staphylococcus

Grape like cluster of circles; Streptococcus are chains of circles after cell division

Tetrad

Spherical bacterial cells arranged in groups of 4 like a square; Sarcina = cubes

Bacillus

Rod shaped in singles; Diplobacillus = rods in pairs; Streptobacillus = chains of rods

Vibrio

Curve comma shaped cells

Spirilla

Cells rigid and spiral shaped; plural = spirillum; every bacteria always multiply in even numbers

Pleomophic

Grow in many shapes

Gram stain

Differential because bacteria divide into 2 groups gram positive and gram negative bacteria

Gram stain

Gram positive retain purple; gram negative lose purple after ETOH and then stain pink

Gram stain

Iodine = mordant used to stain intensely and makes dye stick to cell wall

Gram stain

4 steps= purple then H2O then iodine then ETOH then H2O then pink then H2O then blot

Mycobacterium

Doesn’t stain true appears light purple

Gram staining

Tells us shape and arrangement AND positive or negative; gram neg after ETOH clear

Pseudomonas aeruginosa

Gram negative single rods

Staphylococcus aureus

Gram positive organism; clusters

Escherichia coli

Gram negative organism

Micrococcus luteus

Gram positive cocci ,non motile, aerobic, yellow on plate

Facultative anaerobe

Organism that can grow with or without molecular oxygen; exception to obligate versions because this 1 is both with O2