Difference between revisions of "Bacterial Structure"
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− | + | '''Bacterial genome''': | |
+ | *Contains double-stranded DNA | ||
+ | *Prokaryotic DNA differs to eukaryotic DNA: | ||
+ | **Few repeated sequences | ||
+ | **Most of the DNA is transcribed | ||
+ | **No intervening sequences within structural genes | ||
+ | '''Cytoplasm''': | ||
+ | *Does not contain mitochondria, lysosomes or Golgi bodies (found in eukaryotic cells) | ||
+ | *Contains mesosomes- thought to be primitive endoplasmic reticulum | ||
+ | '''Surface components''':[[Image:478px-Bacteria cell wall svg- franciscosp2.png|thumb|right|100px|'''Structure of cell wall''' Franciscop2 2008, WikiMedia Commons]] | ||
+ | *Fimbriae- also known as pili, these are hair-like structures that allow bacteria to adhere to each other | ||
+ | *F-type pili- also known as sex pili, these act as conjugation tubes during sexual reproduction | ||
+ | *Capsules/slime- serve to adhere bacteria to cells and provide protection from phagocytosis and dehydration, e.g. hyaluronic acid | ||
+ | *Flagella- help the bacteria move around | ||
+ | |||
+ | One way bacteria can be classified is by the structure of the cell wall: | ||
+ | *'''[[:Category:Gram positive bacteria|Gram-positive bacteria]]''': cell wall consists of peptidoglycan layer, with teichoic polymers attached, e.g. ''Staphylococcus'' | ||
+ | *'''[[:Category:Gram negative bacteria|Gram-negative bacteria]]''':peptidoglycan layer is thinner, but surrounded by outer membrane of lipopolysaccharides and lipoproteins, e.g. salmonella | ||
+ | |||
+ | [[Image:427px-Arrangement of bacilli bacteria svg.png|thumb|right|100px|'''Arrangement of bacilli bacteria''' LadyofHats 2006, WikiMedia Commons]] | ||
+ | [[Image:497px-Arrangement of cocci bacteria svg.png|thumb|right|100px|Arrangement of cocci bacteria]] | ||
+ | {| border="1" | ||
+ | |+ Components of bacterial envelope | ||
+ | ! Component !! Gram positive !! Gram negative | ||
+ | |- | ||
+ | ! Peptidoglycan | ||
+ | | Yes || Yes | ||
+ | |- | ||
+ | ! Teichoic acid | ||
+ | |Yes | ||
+ | |No | ||
+ | |- | ||
+ | ! Lipoprotein | ||
+ | |No | ||
+ | |Yes | ||
+ | |- | ||
+ | ! Lipopolysaccharide | ||
+ | |No | ||
+ | |Yes | ||
+ | |- | ||
+ | ! Phospholipid | ||
+ | |No | ||
+ | |Yes | ||
+ | |} | ||
+ | |||
+ | |||
+ | Another method of classification is the shape and arrangement of the bacteria themselves: | ||
+ | |||
+ | *'''[[:Category:Cocci|Cocci]]'''- round shape, e.g. Streptococci, Staphylococci, Neisseria | ||
+ | *'''[[:Category:Rods|Rods]]''' or '''bacilli'''- long shape, e.g. Coliforms, Bacillus, Spirochaetes[[Category:Bacteria]] | ||
+ | [[Category:To_Do_-_Bacteria]] |
Revision as of 10:22, 20 July 2010
Bacterial genome:
- Contains double-stranded DNA
- Prokaryotic DNA differs to eukaryotic DNA:
- Few repeated sequences
- Most of the DNA is transcribed
- No intervening sequences within structural genes
Cytoplasm:
- Does not contain mitochondria, lysosomes or Golgi bodies (found in eukaryotic cells)
- Contains mesosomes- thought to be primitive endoplasmic reticulum
Surface components:
- Fimbriae- also known as pili, these are hair-like structures that allow bacteria to adhere to each other
- F-type pili- also known as sex pili, these act as conjugation tubes during sexual reproduction
- Capsules/slime- serve to adhere bacteria to cells and provide protection from phagocytosis and dehydration, e.g. hyaluronic acid
- Flagella- help the bacteria move around
One way bacteria can be classified is by the structure of the cell wall:
- Gram-positive bacteria: cell wall consists of peptidoglycan layer, with teichoic polymers attached, e.g. Staphylococcus
- Gram-negative bacteria:peptidoglycan layer is thinner, but surrounded by outer membrane of lipopolysaccharides and lipoproteins, e.g. salmonella
Component | Gram positive | Gram negative |
---|---|---|
Peptidoglycan | Yes | Yes |
Teichoic acid | Yes | No |
Lipoprotein | No | Yes |
Lipopolysaccharide | No | Yes |
Phospholipid | No | Yes |
Another method of classification is the shape and arrangement of the bacteria themselves: