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name chacteristics of gram + wall.
- 1.) thick peptidoglycan (many layers)
- 2.) teichoic acid
- 3.) very little lipids
- 4.) no outer membrane
- 5.) exotoxins
- 6.) very sensitive
- 7.) m protein
- 8.) mycolic acid
name chacteristics of - wall.
- 1.) thin layer of peptidoglycan
- 2.) teichoic acid is absent
- 3.) lipopolysacchride layer
- 4.) has an outer membrane (lipopolysaccride + phospholipid- A & O polysachrides)
- 5.) endotoxin
- 6.) moderately sensitive
carb. chains that are part of the outer membrane located on the side of the membrane that faces extracellular fluid. vary from one species to the next. Can be recognized by the immune system. Can be used as diagnostic tool for ID of some bacteria.
what are the components of peptidoglycan?
- -composed of repeating molecules of the sugars N-acetyl muramic acid (NAM) & N-acetyl glucosamine (NAG)
- -small peptide chains (pentaglycine & tetrapeptide)
- -constructed w/ the help of several enzymes; transglycosylase, transpeptidase, polymerase & hydrolase
what are the 3 phases of peptidoglycan assembly?
- 1.) cytoplasmic phase
- 2.) membrane-associated phase
- 3.) extracytoplasmic phase
whats the cytoplasmic phase?
- -NAG/NAM building blocks for peptidoglycan are fashioned in the cytoplasm of the wall
- -the cell wall is ready to divide
- -pep. layers are laid down transversely and vertically as the intracellular partion (or septum) that divides the cell into 2 daughter cells
- -NAG & NAM of pep. are formed by enzymes that are encoded by murA-F genes
- -enzymes coded by these genes attach 5 amino acids to each NAG & NAM molecule
- -pep units have to be formed to build a new cell wall (potential target for antibiotic therapy)
- -antibiotics fosfomycin murA gene activity & thereby prevents pep subunits from being produced
Membrane associated phase?
- -specific NAG & NAM subunits w/ lipid portion of the bacterial cell plasma membrane
- -insertion of NAG & NAM into plasma membrane is performed via the lipid carrier cycle. The 1st step is the bond of pep & the side of plasma membrane facing the cytoplasm.
The extracytoplasmic phase?
- -because the cell wall grows outward from the cell, new subunits must be moved from the inner side of the plasma to the outer.
- -when it arrives on the outside the pep units react w/ a series of membrane-bound enzymes, which allows the new subunits to be incorporated into the cell wall
- -finally pep binds together to form a meshwork w/ help of polypeptide chains
what are teichoic acids? (2 types)
- 1.) wall- goes partway through pep. layers
- 2.) lipoteichoic- goes compeletly through pep layers & link to plasma membrane
- -both protrude above pep. gram + cell has a - charge
what are M proteins?
They are required for infection. Antibodies against it can inhibit infection. highly suseptible to mutations. currently there is 80 different viriants.
whats a mycolic acid?
- -makes up 60% of the cell wall of M TB & M leprae of the myobacterium species.
- -mycolic acid makes the organism very resistent to enviromental stress
- -mycolic acid into cell wall provides a barrier that prevents the action of antibiotics & many host mechanisms
what are lipid A?
- -anchors LPS poriton of the outer membrane to phopholipid bilayer portion
- -lipid A is released as a by product of bacterial cell death= endotoxin (body defenses can overreact to it and eventually have adverse effect on host cells)
- can be slime layer or a capsule. both allow it to adhere to things.
- it is a sticky substance composed of polypeptides (difference between the ones in our cells and bacterial cells) & polysachrides
- produced in cytoplasm and is secreted to outer cell wall
- protective element against enviromental stress
- can be used for nutrition
- bacteria can draw back in sugar for use of energy
- loosely attached
- indicative of dental decay
- firmly attached
- inhibits pahgocytosis
- many organims are not infectious w/o a capsule
- capsule genes can be transfered between organisms
fimbriae and pili
- both involved w/ adherence (atachment to surfaces)
- both appear as sticky projections which appear shorter than flagella
- they are found on gram - organims
- both are composed of pillin subunits
- both appear as imprtant structures for pahtogenic bacteria
- hairlike structures are shorter than flagella
- hairs are everywhere to coat the cel
- Used for DNA transfer through conjuntion
- only one or 2 are present in a cell
- used for motility
- long structures that extend far beyond the cell wall and even the glycocaylx
- 4 configurations
4 flagella configurations
- monotrichous: 1 flagellum located at the end of the cell
- amphitrichous: 2 flagella 1 at each end
- lophotrichous: 2 flgella located at same end
- peritrichous: flagella all over
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