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Figure 1-A-2. Schematic drawing of a prokaryotic cell. The plasma membrane is surrounded by the cell wall (blue), which is wrapped by the capsule (red).
A prokaryotic cell consists of DNA, cytoplasm, and a surface structure which includes the plasma membrane and some of the following components:
In bacteria, the cell wall contains a unique structure called peptidoglycan. Archaea do not possess peptidoglycan, but some archaea may contain pseudopeptidoglycan, which is composed of N-acetyltalosaminuronic acid, instead of N-acetylmuramic in peptidoglycan. Because of this structural difference, archaea are resistant to many cell wall antibiotics.
Bacteria may be divided into two groups, on the basis of their cell wall structures and the response to Gram stain: Gram-negative and Gram-positive.
Capsule and slime are the hydrophilic gel surrounding the cell wall in most bacteria. The capsule is more closely associated with the cell than the slime. Flagella are long, rigid protein rods, facilitating the movement of motile bacteria. Fimbriae and pili are short hair-like structures used to attach other cells. They are essential for infecting other organisms.
Spores The spore is a small, often unicellular, reproductive unit of plants, algae, fungi, protozoa, and bacteria. Bacterial spores have thick walls which can withstand varying temperatures, humidity, and other unfavorable conditions.
Online Textbooks: Medical Microbiology Textbook - From University of Texas Medical Branch Microbiology and Immunology Online - From University of South Carolina Review Articles: Protein secretion and the pathogenesis of bacterial infections - Genes and Development, 2001. The languages of bacteria - Genes and Development, 2001.
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