Domains:

BacteriaArchea

Two Lineages

•Archaebacteria

•Eubacteria

Metabolic Diversity

• Photoautotroph

• Photoheterotroph

• Chemoautotroph

• Chemoheterotroph

Archaebateria

•Methanogens

•Extreme halophiles

•Thermoacidophiles

Archaebacteria have Different Characteristics• They have unusual proteins

• They have introns within their mRNA.

• They lack peptidoglycan.

Eubacteria

•Most bacteria•2 basic types

–Gram +–Gram -

Types of Cell Shapes

Coccus Bacillus Spirillium Spirochete

Cell Groupings

or

singles

or

diplo

or strepto

staphylo

Gram Staining• Developed by the Danish bacteriologist, C.

Gram, as a way to differentiate between bacteria.

• Divides bacteria into two groups based on their cell wall composition.– G (+) Single layered cell wall with a low lipid

content.

– G (-) 3 layered cell wall with a high lipid content.

Why a Gram Stain?

• To gain knowledge about a bacteria’s structure and grouping arrangements

• Taxonomic purposes

• Medical reasons– Doctors can use the Gram stain results to help

properly diagnose and treat bacterial infections.

What can we tell about a bacteria’s structure?

• Cell shape

• Cell groupings

• Presence of endospores

• Cell wall content

• Approximate size

Presence of Endospores

Endospores are found only in bacilli

Central terminal

Cell Wall Composition

• Basis of the Theory behind the Gram Stain

– G (+) bacteria retain the primary stain (crystal violet) because the decolorizer does not dissolve it’s cell wall (peptidoglycan)

– G (-) bacteria lose the primary stain because the decolorizer dissolves a portion of the cell wall (lipopolysaccharide) releasing with the primary stain.

Here’s how it works .Crystal Violet is added, staining the cell walls.

Iodine is then added "locking" the stain onto the cell walls.

(Primary Stain)

(Mordant)

Decolorization results in the high lipid content cell wall being washed away leaving the

Gram (-) cell wall colorless.

Safranin (secondary stain) is then used to stain any cell walls left unstained after

decolorization

Gram (+) Gram (-)

Kingdom Eubacteria

• Phylum Cyanobacteria

• Phylum Spirochetes

• Phylum Gram-Positive Bacteria

• Phylum Proteobacteria

Phylum Cyanobacteria

• Photosynthetic

• Blue-green algae but considered eubacteria as they lack a membrane-bound nucleus and chloroplasts.

• Grow in chains. Some cells become specialized cells called heterocysts that have the ability to fix N2.

Phylum Cyanobacteria (cont.)

• A sudden increase in the number of cyanobacteria in a body of water due to an increase in phosphates and nitrates is called eutrophication (population bloom).

• Can cause fish kill due to decay of cyanobacteria and lack of O2 and nutrients.

Phylum Spirochetes• Gram-(-), spiral-shaped

heterotrophic bacteria

• Can be aerobic or anaerobic

• Corkskrew rotation

• Commensal, mutualistic, or parasitic.

• Treponema pallidum (syphilis)

Phylum Gram-Positive Bacteria• Does include some G(-) bacteria.• Includes Steptococcus (Strep throat) and

Staphylococcus (sinus infections and boils).• Lactobacilli responsible for tooth decay

(secrete an acid).• A gram positive converts milk into yogurt.• Actinomycetes produce antibiotics. Are

recognized by their branching filaments.

STAPHYLOCOCCUS INFECTION

Proteobacteria• Enteric bacteria: Gr. - lives in

the intestines e.g. Salmonella, E. coli

• Chemoautotrophs: Gram (-) bacteria that extract energy by oxidizing minerals e.g. Rhizobium (a N2 fixing bacteria).