Introduction to Bacteria: Classification, Morphology and Structures

Introduction
• Prokaryotic organisms. • Vary in sizes, measure approximately 0.1 to 10.0 ?m • Widely distributed. It can be found in soil, air, water, and living bodies. • Some bacteria can cause diseases for human, animals and plants. • Some bacteria are harmless (i.e. live in human bodies as normal flora)
Size of Bacteria
• Unit of measurement in bacteriology is the micron (micrometre, µm) • Bacteria of medical importance (0.2 – 1.5 µm) in diameter (3 – 5 µm) in length
Bacterial Morphology
• Rods – bacilli


• Coccoid shaped


• spirilla
Bacterial Morphology
• Cocci – spherical / oval shaped major groups • Bacilli – rod shaped • Vibrios – comma shaped • Spirilla – rigid spiral forms • Spirochetes – flexible spiral forms • Actinomycetes – branching filamentous bacteria • Mycoplasmas – lack cell wallCharacteristic Gram-negative Bacteria Gram-positive Bacteria
Wall Structure They have a thin lipopolysaccharide exterior cell wall.
The peptidoglycan layer is thick
Effect of Dye do not retain the crystal violet dye, and react only with a counter-stain, generally stain pink.
retain the crystal violet dye, and change into purple during staining identification.
Effect of Antibiotics • resistant to penicillin • contain an endotoxin called LPS
susceptible to the enzyme lysozyme and to penicillin
Flagellum If present, the flagellum has four supporting rings, namely L ring, P ring, M ring, and S ring.
The flagellum has two supporting rings, in the peptidoglycan layer, and in the plasma membrane.
Teichoic Acids absent. present.
Liproproteins They are attached to the polysaccharide backbone.
absent.
Periplasmic Space present. absent.
Bacterial Structure

Bacterial Structure
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