Chapter 4

Prokaryote

One circular chromosome not in a membrane

• No histones

• No organelles

• Bacteria: peptidoglycan cell walls

• Archaea: pseudomurein cell walls

• Divides by binary fission

Eukaryote

Paired chromosomes in a nuclear membrane

• Histones

• Organelles

• Polysaccharide cell walls, when present

• Divides by mitosis

most bacteria are

monomorphic

Bacillus

rod shaped

Coccus

spherical shaped

Pairs

diplococci, diplobacilli

clusters

staphylococci

Chains

streptococci, streptobacilli

Groups of four

tetrads

Cubelike groups of eight

sarcinae

Glycocalyx

External to the cell wall

• Viscous and gelatinous

• Made of polysaccharide and/or polypeptide

Capsule

neatly organized and firmly attached

slime wall

unorganized and loose

Contribute to virulence

– Capsules prevent phagocytosis

– Extracellular polymeric substance helps form biofilms

Flagellum

• Filamentous appendages external of the cell

• Propel bacteria

• Made of protein flagellin

Filament

outermost region

hook

attaches to the filament

Basal body

consists of rods and pairs of rings, anchors flagellum to the cell wall and membrane

Flagella proteins are

H antigens and distinguish among serovars

the cell wall

Prevents osmotic lysis and protects the cell membrane

Made of peptidoglycan (in bacteria)

Contributes to pathogenicity

axial filaments

• Also called endoflagella

• Found in spirochetes

• Anchored at one end of a cell

• Rotation causes the cell to move like a corkscrew

Fimbriae

hair-like appendages that allow for attachment

Pili

motility, Conjugation pili involved in DNA transfer from one cell to the other

Peptidoglycan

Polymer of a repeating disaccharide in rows:

▪ N-acetylglucosamine (NAG)

▪ N-acetylmuramic acid (NAM)

Rows are linked by pentapeptides

gram positive cell walls

Thick peptidoglycan, Teichoic acids

Teichoic acids

• Lipoteichoic acid links cell wall to plasma membrane

• Wall teichoic acid links the peptidoglycan

• Carry a negative charge

• Regulate movement of cations

• Provide antigenic specificity