Prokaryotic Cell Structure and Function

Size of Bacteria

• Average bacteria 0.5 - 2.0 um in diam.

– RBC is 7.5 um in diam.– Pulopiscium fishelsoni, bacillus (80µm in

diameter and 200-600 µm long)– Thiomargarita namibiensis, sperical (100-

750 µm in diameter.)

Shapes of Bacteria

• Coccus• Bacillus• Coccobacillus• Vibrio• Spirillum• Spirochete

Spherical BacteriaAn average coccus is about

0.5-1.0 micrometer (µm) in diameter.

A. Division in one plane.

• Diplococcus: cocci arranged in pairs

• Streptococcus: cocci arranged in chains

• Streptococcus pneumoniae,

• Streptococcus pyogenes,

Spherical Bacteria

B. Division in two planes.

• tetrad: cocci arranged in squares of 4

C. Division in three planes

• Sarcina: cocci in arranged cubes of 8

sarcina

Spherical Bacteria

D. Division in random planes

• Staphylococcus: cocci arranged in irregular, often grape-like clusters

Rod-Shaped Bacteria

• Diplobacillus

• Coccobacillus

• Streptobacillus

Spiral-Shaped Bacteria

• Spirochete

• Spirillum

Cell Structures

• Cell Membrane

• Cytoplasm

• Cell Wall

• Components external to cell wall – Flagella – Pili– Capsule/ Slime layer

Cell Membrane

• Hydrophobic Proteins

• Bilayer Phospholipid – Triclosan-enoyl transferase

• Hopanoids

Membrane proteins

• Structural support

• Detection of environmental signals– ToxR- Vibrio cholera

• Secretion of virulence factor and communication signals– NodI and NodJ-Rhizobia

Membrane lipids

• Phosphoryl heads– Negative-phosphatidate

• Phosphatidylglycerol• Cardiolipin

– Positive-Phosphatidylethanolamine• DNA interaction

• transporter protein

• Fatty acids– Saturated straight chain (6-22) – Unsaturated

• Oleic acid (cis)– Cyclopropane