Bacterial Classification and Structure

Capsule Gelatinous layer surrounding the bacterial cell; gives many bacterial colonies a mucoid appearance. Composed of polysaccharide (except in Bacillus anthracis) which varies among bacteria

1. Cytoplasmic (Cell) Membrane Located just inside the peptidoglycan layer. Phospholipid bilayer similar to eukaryotic membranes, but does not contain sterols (except Mycoplasma species). Functions:

like a stiff “canvas sack” around the bacterial cell. maintains cell structure. is a permeability barrier to large molecules (like lysozyme) and hydrophobic molecules; also

Structure Chemical Composition Function Essential Components Cell Wall   Peptidoglycan         Outer membrane of Gram- negative bacteria     Surface fibers of

Name Reason Alternative Microscopic Approach Mycobacteria (Ex. M. tuberculosis) Too much lipid in cell wall so dye cannot penetrate Acid-fast stain Treponema pallidum Too thin

It is difficult to classify all bacteria into clear-cut categories.  Various classification methods are used, depending in part, on the purpose.   Nomenclature Bacteria are

  Property Prokaryotic Bacterial Cells Eukaryotic Human Cells DNA within a nuclear membrane No Yes Number of chromosomes 1 More than 1 Mechanism of Replication

Learning Objectives: You should be able to: describe the major differences between eukaryotic and prokaryotic cells and explain why it is important to know the