Bacterial Structure

Chapter 6


Bacterial Structure




Bacterial Morphology



Overview



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)

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

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

Full access? Get Clinical Tree

Get Clinical Tree app for offline access