Test3

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Exotoxin

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a highly specific protein produced inside some Gram Positive Bacteria that is then secreted or released.

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Which microbes make exotoxins?

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Bacteria that produce exotoxins can be gram negative but is predominately gram positive

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What is the Function of an Exotoxin?

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The function of an Exotoxin is to poison body parts or interfere with activities in the body.

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Exotoxins work....
(3)

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-destroying certain parts of host cells

-inhibit certain metabolic functions

-highly specific in body tissues

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Exotoxins are....
(3)

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-soluble in body fluids

-can easily diffuse into the blood and are transported throughout the body.

-among the most lethal substances

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Functional types of Exotoxins (3)

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1. Cytotoxin (may also damage tissues or organs)

2. Neurotoxin (damages nerves-causes paralysis or spasms)

3.Enterotoxin (Food-poison)

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3 Structural Types of Exotoxins

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1. A-B Exotoxins

2.Membrane-Disrupting Exotoxins

3.Superantigen Exotoxins

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Exotoxin (4)
A-B toxins

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-consist of two parts designated A and B.

-The A part is the active (enzyme) component and the B part is the binding component.

-The A-B components of the exotoxin separate. The A component alters the function of the host cell by inhibiting protein synthesis.

-The B component is released from the host cell, and the receptor is inserted into the plasma membrane for reuse.

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Exotoxins
Membrane-Disrupting Toxins

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-cause lysis of host cells by disrupting their plasma membranes.

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Exotoxins (3)
Superantigens

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-Bacterial proteins; antigens that provoke a very intense immune response.

-stimulates the proliferation of immune cells called T-cells. These cells are types of white blood cells (lymphocytes).

-In response to superantigens, T-cells are stimulated to release enormous amounts of chemicals called cytokines.

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Exotoxins- Superantigens
Cytokines

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-small protein molecules produced by various body cells, especially T Cells, that regulate immune responses.

-excessively high levels of cytokines released by T cells enter the blood stream and give rise to a number of symptoms including fever, nausea, vomiting, diarrhea, and sometimes shock and even death.

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ANTITOXINS

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The body produces antibodies that provide immunity to exotoxins.

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TOXOID

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The denatured or inactivated Exotoxin which is useful as a vaccine to induce immunity and stimulate antibody production.

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BOTULINUM EXOTOXIN
common clinical form:

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Clostridium botulinum (botox)

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BOTULINUM EXOTOXIN
How many types exist?

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7 types of Exotoxins: A-G

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BOTULINUM EXOTOXIN
lethal doses:

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A lethal dose of 135-150ng of Botox is considered fatal

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Which Botulinum Exotoxin type has cosmetic value?

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-Type-A (the deadliest of all 7 types)

-A cosmetic dose of BOTOX® is just about 20 - 50 units

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ENDOTOXINS

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-part of the outer portion of the cell wall of gram negative bacteria

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Gram-negative bacteria...

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-have an outer membrane surrounding the peptidoglycan layer of the cell wall.

-the outer membrane consists of lipoproteins, phospholipids, & lipopolysaccharides (LPS).

-LPS aka Lipid A is the endotoxin

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How do endotoxins work? (2)

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-Endotoxins are released when gram-negative bacteria die and their cells undergo lysis resulting in releasing the endotoxin.

-Endotoxins are also released during bacterial multiplication.

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How does the use of antibiotics affect endotoxins?

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-Antibiotics used to treat diseases caused by gram-negative bacteria can lyse the bacterial cells.

-This reaction releases endotoxin and may lead to an immediate worsening of symptoms.

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What are the symptoms of endotoxins? (2)

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-endotoxins exert their effects by stimulating macrophages to release cytokines in very high concentrations. At these levels cytokines are toxic.

-all endotoxins show the same symptoms: chills, fever, weakness, generalized aches, and in some cases shock and even death.

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Shock

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-refers to any life threatening decrease in blood pressure.

-shock caused by a bacteria is called septic shock.

-Gram-negative bacteria cause endotoxic shock.

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List characteristics of Microbial Life (8)

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1. Irritability-Respond to the Environment

2. Movement

3. Nutrition-Eat & Consume Food

4. Metabolism- Process Food

5. Respiration-Breath

6. Excretion-Get rid of Metabolic wastes

7. Growth-Grow & Develop

8. Reproduction-Reproduce "...their kind"

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Minimum Conditions

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the lowest condition or amount microbes need to initiate development; growth may not occur below this point.

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Optimum Conditions

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most favorable condition or amount for organism.

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Maximum Conditions

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highest condition or quantity microbes can endure; beyond this, growth is impaired & microbial death may occur.

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What is the purpose of Respiration?

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-an ATP generating process

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Positive Stimuli

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attract living things because they indicate environments that support life and promote growth, or stimulate development.

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Negative Stimuli

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repel because they signal danger or environments that could impede life and inhibit microbial growth or development.

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Requirements for growth

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-divided into two main categories: physical & chemical.

-physical aspects include temperature, pH, & osmotic pressure.

-chemical requirements include sources from carbon, nitrogen, sulfur, phosphorus, oxygen, trace elements, and organic growth factors.

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Describe a capsule (4)

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-glycocalyx (sugar coat) is a substance secreted by prokaryotes

-its sticky and is external to the cell wall and composed of polysaccharide, polypeptide, or both.

-If the substance is organized and is firmly attached to the cell wall, the glycocalyx is described as a capsule.

-If the substance is unorganized and only loosely attched to the cell wall, the glycocalyx is described as a slime layer

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What is a capsule made of?

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-composed of polysaccharide, polypeptide, or both.

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What is a capsule's function?

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-capsules are important in contributing to bacterial virulence (the degree to which a pathogen causes disease)

-capsule often protect pathegenic bacteria from phagocytosis by the cells of the host.

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What groups of dyes are used for Capsule staining?

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-Flurochrome & Immuno-fluorescence microscopy

-Negative staining

-Nigrosin dye

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Fimbraie (4)

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-are numerous short hair-like appendages of Gram-negative bacteria.

-occur at the poles of the bacterial cell or can be evenly distributed over the entire surface of the cell

-can number anywhere from a few to several hundred per cell.

-has a tendency to adhere to each other and to the surface.

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What does fimbraie do for bacteria?

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-can help bacteria adhere to epithelial surfaces in the body

-once colonization occurs, the bacteria can cause disease.

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Pili

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-usually longer than fimbraie and number only one or two per cell.

-involved in motility and DNA transfer

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What does pili do for bacteria?

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Bacteria specifically use the Pilus to attach to other bacteria, forming a tube through which genetic material can be transferred between cells (Conjugation (sex) pili)

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Mycolic Acid

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-the acid-fast stain is used to identify all bacteria of the genus Mycobacterium and pathogenic species of Nocardia.

-these bacteria contain high concentrations (60%) of a hydrophobic waxy lipid in their cell walls that prevent the uptakes of dyes

-the mycolic acid forms a layer outside of a thin layer of peptidoglycan

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Staining Mycolic Acid bacteria
Dyes

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1. carbol fuchsin
2. counter stain- methylene blue

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What is an endospore?

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-A special resistant, dormant structure formed within a cell that protects a bacterium from adverse environmental conditions.

-formed by few genera like bacillus and clostridium

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Sizes of Endospores

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-Bacillus- generally produce normal or under-sized endospores. Therefore, the cells look regular with no bulge.


-Clostridium-oversized spores
tend to be over-sized. Therefore, the cells appear swollen to accommodate the endospores

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Location of Endospores

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1. Central- are exactly in the middle and may be smaller, bigger, or same size as the cell.

2. Subterminal -occur anywhere between the middle and end of the cell and may be smaller, bigger, or same size as the cell.


3. Terminal- are at either end of the cell and may be smaller, bigger, or same size as the cell.

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Tetanus

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A Gram Positive bacterium with an over-sized, terminal, endospore that makes it look like a drumstick is typical of the disease agent for