Bacterial Structure

Chapter 6

Bacterial Structure

Bacterial Morphology


1. Bacteria are prokaryotes

2. The differences between eukaryotic and prokaryotic cells, summarized in Table 6-1, are the basis for antimicrobial drugs.

Size of bacterial cells

Shape and arrangement of common bacteria (Fig. 6-1)

Gram staining

II Bacterial Ultrastructure

• Gram-positive and gram-negative bacteria have similar internal structures but structurally dissimilar cell envelopes (Fig. 6-2; Table 6-2).

Internal bacterial structures

1. Nucleoid is the central region of bacterium that contains DNA.

2. Bacterial cells contain a single chromosome composed of a circular DNA molecule.

3. Because bacteria lack a nuclear membrane, transcription and translation are coupled (i.e., ribosome-mediated protein synthesis can begin while a messenger RNA [mRNA] is being produced and is still attached to the DNA).

4. Bacterial ribosomes differ in size, components, and shape from eukaryotic ribosomes and thus are a major target of antibiotic action.

5. Plasmids, which are small, circular fragments of extrachromosomal DNA, may be present and often carry antibiotic resistance genes.

Cell envelope (Table 6-3)

• Bacterial cell envelope = cytoplasmic membrane + cell wall

1. Cytoplasmic (cell, plasma) membrane

2. Cell wall of gram-positive bacteria (Fig. 6-3A)

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Jun 18, 2016 | Posted by in IMMUNOLOGY | Comments Off on Bacterial Structure
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