Bacterial Structure 2&3. 3 Flashcards
Cell wall of bacteria
a structure exterior to the cell membrane that provides rigidity and stability to the bacterial cell
- Cell walls consist of Peptidoglycan
- G- or G+
Gram (+) composed of?
peptidoglycan and teichoic acid (purple)
Gram (-) composed of?
peptidoglycan and an outer membrane (red)
Peptidoglycan consists of?
strands of alternating repeats of N-acetyl glucose-like sugars
•N-acetylglucosamine (NAG)
•N-acetylmuramic acid (NAM)
N-acetylmuramic acid (NAM) is cross linked between?
strands by short peptides
Our body prodcuces what enzyme that destroys peptidoglycan? This leads to?
Lysozyme
*leads to lysis of bacteria cell
NAG and NAM are linked by?
a beta 1-4 glycosidic covalent bond -this is the lysozyme sensitive region
What four AA make the tetrapeptide bound to NAM in peptidoglycan?
- L-alanine
- D-alanine
- D-glutamic acid
- either lysine or diaminopimelic acid
Tetrapeptide cross-links are formed by? Provide the cell wall with what physical traits?
Tetrapeptides interaction on separate strands of peptidoglycan; provide the cell wall of prokaryotes with extreme strength and rigidity
define peptidoglycan interbridge
Tetrapeptide cross-links between layers of peptidoglycan
In G+, peptidoglycan interbridge is often?
a pentaglycine
In G-, peptidoglycan interbridge is often?
a direct link between one tetrapeptide that often contains a diaminopimelic acid (DAP) and the other tetrapeptide
Penicillin preevnts?
prevents crosslinkage of cell wall peptidoglycan (weakening the cell wall) aka transpeptidation
A hydrophobic alcohol called _______ facilitates transport of new glycan units across cytoplasmic membrane for formation of peptidoglycan
bactoprenol
bactoprenol and vancomycin inhibit?
the bactoprenal dependent process of transporting glycan units across cytoplasm
How thick is G+ Peptidoglycan layer? composed of?
- about 200-800 Angstroms (1 Angstrom = 10-8 centimeter) thick
- composed of many layers of peptidoglycan
Teichoic acids are associated with
peptidoglycan of Gram (+) bacteria
Teichoic acids function in? Bind?
adherence; binds Mg++ ions for the cell
describe the 3 types of Teichoic acid
1) one type -contains glycerols (3-carbon sugar alcohol) repeated again and again and linked by phosphates with D-ala or Dglucose 2) second type -contains ribitols (a 5- carbon sugar alcohol) repeated again and again linked by phosphates with D-ala or D-glucose 3) third type - lipoteichoic – contains glycerols or ribitols with a terminal fatty acid that is integrated into the cytoplasmic membrane
Mycobacteria is? contain? Peptidoglycan is bound with?
an acid fast bacteria
- contain mycolic acid layer that is exterior to peptidoglycan (mycobacteria outer membrane)
- Peptidoglycan is bound with Arabinogalactan
In addition to peptidoglycan, the outer membrane of G- contain?
- lipopolysaccharide (LPS),
- proteins
- Lipoproteins
- Phospholipids
- type I, II, III, IV, and V secretion devices
Periplasm
space between membranes, contains other proteins, mainly for transport
Porin proteins are integrated with?
*Provides channel for?
both leaflets of the outer
membranes of G-
*provide a channel to shuttle small nutrients from the outside to the inside
G- bacteria have an outer membrane that can be? Therefore it is referred to as?
physiologically toxic to the host during an infection
*referred to as endotoxin
Shwartzman reaction follows the release of large amounts of?
endotoxin into the bloodstream
Neisseria bacteria shed large amounts of a related molecule to endotoxin called lipooligosaccharide (LOS). This results in?
resulting in fever and severe
symptoms
penicillin is much less effective against Gram (-) or Gram (+) peptidoglycan? Why?
Gram (-) peptidoglycan
*Peptidoglycan of Gram (-) bacteria is thicker! But no more than 1 to 2 layers
Exterior portion of Lipopolysaccharides of G- are composed of
“O” specific polysaccharide
“O” specific polysaccharide are often called?
Has a what motif?
- often called repeat polysaccharide (up to 40x)
* has various six carbon sugar motifs that are repeated again and again
Middle portions of Lipopolysaccharides of G- are composed of ?
core polysaccharide-that contains •ketodeoxyoctonate (KDO), •heptoses, •glucose, •galactose, •NAG (N-acetylglucosamine)
•Inner portions of Lipopolysaccharides of G- are composed of?
*•Lipid A
•diphospho-(NAG)2
•fatty acids are attached
•Lipooligosaccharide (LOS) of Neisseria species lacks the O-antigen portion of LPS, has a core polysaccharide plus lipid A, and is readily shed from the Neisseria bacteria
example of endotoxin
G- bacteria’souter membrane- can be physiologically toxic to the host during an infection
Protoplasts are?
are wallless bacteria that can survive in isotonic solutions but not hypotonic solutions
•In hypotonic solutions protoplasts lyse
How is it possible for a protoplast to survive without a cell wall?
How do the mycoplasma species do it?
1) produce unusually tough membranes
2) live in osmotically protected habitats, such as the animal body =Mycoplasma species**
3) evolve to survive in an animal body without cell walls due to selective pressure of penicillin (L-forms). They are penicillin resistant
Gram stain reaction gives us what information?
If the bacteria is G+ (purple) or G- (red)
What is responsible for differences in the Gram stain reaction?
The structural differences between the cell walls of gram-positive and gram-negative Bacteria
Alcohol can readily penetrate the lipid rich outer membrane of? Alcohol then extracts?
G- bacteria
*alcohol extracts the insoluble crystal violet-iodine complex from the cell
