Lecture 4 Flashcards
A few bacterial cell types, notable Mycobacteria tuberculosis, contains large amounts of ____ which are complex long chain hydrocarbons with sugars and other modifying groups.
Waxes
The dye carbolfucin is used in _____ stains. Which bacterial group (genus) is identified by this method?
acid fast; Mycobacteria
What layers are found in gram positive bacteria?
It has multiple layers of peptidoglycan in the cell wall.
- teichoic acid
- lipoteichoic acid
- murein (thick cell wall)
What layers are found in gram negative bacteria?
- lipopolysaccharide
- phospholipid
- lipoprotein
- murein (thin layer)
- membrane proteins
What is a peptidoglycan?
- a crystal lattice structure formed from linear chains of two alternating amino sugars
- polysaccharide chains with peptide crosslinks
What does a peptidoglycan do for bacteria cell walls?
It is responsible for the rigidity of the cell, morphology of bacteria, and resistance to the internal osmotic pressure.
What is NAG?
- a type of peptidoglycan
- N-acetylglucosamine
- also called GlcNAc
What is NAM?
- a type of peptidoglycan
- N-acetylmuramic acid
- also called MurNAc
How are NAM and NAG connected?
Beta 1-4 linkages
What shape are bacilli bacteria?
rod shaped
What shape are cocci bacteria?
sphere shaped
What shape are spirilla bacteria?
helix shaped
In gram negative bacteria, what does the lipid bilayer do?
- anchors LPS
* anchors various transport proteins
What is below the outer membrane of gram negative bacteria? What happens there?
- periplasmic space is below the outer membrane
* it is the site of hydrolytic enzymes, transpeptidases, or drug binding proteins
In E. coli, what is between the outer membrane and inner membrane?
A single layer of peptidoglycan embedded inside of the periplasic space.
What is found in the outer membrane of a gram negative bacteria?
- LPS (lipopolysaccharide)
* special channels called porins
Describe the 3 parts of a LPS.
- above core (repetitive polysaccharide unit called the “O antigen”)
- central (core polysaccharide)
- below core (Lipid A)
What is the O antigen of a LPS and what does it do?
It protrudes outside the gram negative envelope and excludes hydrophobic toxic molecules from entering.
What is Lipid A of a LPS and what does it do?
It is a phosphorylated disaccharide with attached branched chain fatty acids. It makes up the toxic moiety of gram negative bacteria (endotoxin).
What is the outer membrane of a gram negative bacteria impervious too?
It is impervious to hydrophilic molecules.
What do porins do in the outer membrane of gram negative bacteria?
They are channels that permit passive diffusion of small hydrophilic compounds like sugars and amino acids.
What would happen to bacteria if the cell wall is removed by treatment with lysozyme or treatment with penicillin during active growth?
The bacteria are lysed and die.
What is a protoplast?
- originates from gram positive
* it is the osmotically sensitive sphere formed upon treatment with lysozyme
What is a spheroplast?
- originates from gram negative bacteria (does not completely shed peptidoglycan due to the outer membrane)
- it is the osmotically sensitive sphere formed upon treatment with lysozyme
How is acid fast stained?
- Basic dye (carbolfuchsin)
- Wash with acid alcohol (1 or 2%)
- Background stain with methylene blue (it stains everything but the bacteria)
What is the 1st stain chemical used in gram staining and acid fast staining?
- gram staining: crystal violet
* acid fast staining: carbolfuchsin
Describe what happens to bacteria during acid fast staining with an acid alcohol solution.
The organisms resist decolorization.
What are some examples of what can be stained by acid fast?
- Mycobacteria tuberculosis
* Cryptosporidium
The waxy coat of acid fast contains what?
It is interlaced with murrain, polysaccharides, and lipids.
What is the purpose of the waxy coat of acid fast?
It provides protection for mycobacteria from being killed by white blood cells.
Why do acid fast grow slowly? What is the time frame of division?
Because of the rate of uptake of nutrients is limited by the waxy covering. They divide once every 24 hours, which is slow.
What is wax very rich in?
Unusual lipids (mycelia acid)
What does the wax form in acid fast?
It forms a hydrophobic barrier, impervious to acids, and is responsible for the “acid fast” characteristic of Mycobacteria
Describe how tuberculosis spreads and how the body reacts to it.
- spreads by cough of small drops of saliva that may contain the TB micro bacteria which are breathed in by another person and can travel into their respiratory tract and lungs to cause infection
- the body detects the invasion and sends out macrophages which eats the bacteria and sends it to the lymph nodes where the bacteria is neutralized
What is latent tuberculosis?
When a person has neutralized tuberculosis bacteria. They have the bacterium, but they are not sick.
What percentage of the world is infected with tuberculosis?
33%–however, only a small percentage become sick
What percentage of TB cases become sick? What age range is affected?
5%–normally children because their immune systems are not fully developed
What is active TB?
When latent TB wakes up, possibly months or years later. It can happen in adults with weakened immune systems (HIV +, chemo patients, organ transplant patients)
How does TB spread?
Once it is in the lungs, it spreads through the blood stream or the lymphatic system to other parts of the body (lymph nodes, bones, joints, digestive system, central nervous system, liver, and heart).
What happens when someone has active TB?
If the infection is in the lungs, the patient will cough, have difficulty breathing, and have chest pains. If the symptoms persist with fever, night sweats, and weightless, it is signs for TB. They’ll see the doctor and receive treatment.
What is the most common area for TB to infect in the human body?
In the lungs
