Ultra-structure of bacteria

“Bacteria are unicellular prokaryotic organisms where the organisms lack a couple of organelles and a
true nucleus”.
• Bacterial cells have a simpler internal structure, which lacks all membrane-bound cell organelles such
as mitochondria, lysosome, Golgi, endoplasmic reticulum, chloroplast, and true vacuole, etc.
• All the action takes place within the cytosol or cytoplasmic membrane
• Bacteria also lack a true membrane-bound nucleus and nucleolus. The bacterial nucleus is understood as
nucleoid.
• Most bacteria possess peptidoglycan, a singular polymer that creates its synthesis
• Peptidoglycan may be a good target for antibiotics.
• Protein synthesis takes place within the cytosol with structurally different ribosome’s

Size
• 0.2 µm – 0.1 mm
• Most 0.5 – 5.0 µm

Shape
• Coccus (cocci)
• rod (bacillus, bacilli)
• spiral shapes (spirochetes;
spirillum, spirilla)
• filamentous and various odd
shapes.

Arrangement
• Clusters
• Tetrads
• Pairs
• chains

Structures Outside the Cell Wall

Capsule
Flagella
Pili

Structures Inside the Cell Wall

Cell wall
Cytoplasmic membrane
Nucleoid
Mesosome
Ribosome
cytoplasm