Bacteria Morphology and Gram Staining STEM PREP 2013 – 7th GRADE

July 24, 2013

Dr. Farnsworth

Objectives

• Learn about different bacterial morphology

• Shapes

• arrangement

• Learn about simple staining and Gram staining

• Briefly discuss different bacterial staining techniques

Bacterial Shapes

• Common shapes and structures

• Coccus plural coccii

• Bacillus, plural bacilli

• Spiral- resemble little corkscrews

• Other Shapes

Arrangements of Bacteria • Single

• Diploid

• Di means two

• Strepto- form long chains

• Tetrad

• Sarcina- shape of eight, look like cubes

• Staphylo- grape-like clusters

Cocci • Are spherical

• Can be oval, elongated or flattened on one side

• Dipplococci

• Streptococci

• Tetrads

• Sarcinae

• Staphylococci

Bacilli

• Rod-shaped

• Single

• Diplobacillus

• Streptobacillus

• Coccobacillus

• Roundish-rodish

Spiral Bacteria • Have twists in them

• Vibrio

• Spirillum

• Spirochete

• https://www.youtube.com/watch?v=Gpavfy9bIGY

Other Shapes

• Many other shapes

Outer structures on Bacteria • Capsules e.g. S. pneumoniae

• Flagella e.g. E. coli

• Endospores e.g. B. anthracis

• Virulence factors • https://www.youtube.com/watch?v=4hexn-DtSt4

• https://www.youtube.com/watch?v=wMkMRXu2tVA

Observation of Bacteria • Need microscope

• Simple Stain- one dye, view bacterial shape, size and arrangement.

• Differential stain- uses two different dyes in order to view subpopulations of bacterial cells

• Gram staining

• acid fast

• Special stains used for visualizing different structures of bacteria, e.g. flagella, capsules, endospores

Gram Staining • Most popular stain in microbiology

• Differentiate bacteria based on cell wall properties

• Gram negative

• Gram positive

Gram negative cell wall • Thin peptidoglycan layer

• Outer membrane and inner membrane

• Periplasmic layer in between mebranes

• Lipopolysaccharide (LPS)

• Stain pink with Gram stain

• Tend to be more virulent

• Antibiotics don’t work very well on them

• Examples: E. coli

Gram Positive Cell Wall • Thick peptidoglycan

• Single membrane

• Contain teichoic acid

• Stain purple with Gram stain

• Examples: Bacillus, Streptococcus

Gram Positive Gram Negative

Steps of the Gram Stain

Gram Stain- Important Information

• Mordant

• fixes dye

• iodine

• Alcohol- Not too much

• Not too much

• Will wash away crystal violet

Lab Today

• Simple Stain

• Crystal violet used to stain cells

• Gram Stain

• Thursday