1. What properties of a pathogen dictate whether it is transmitted directly person to person or not?

If the pathogen can survive outside of the body and for how long dictates whether or not the pathogen will be spread person to person.  If the pathogen can form a spore it will most likely not spread person to person because it can survive outside of the host for a long time.

2. What is a spore?  What is it composed of?  How is it different from a vegetative cell?

A spore is a differentiated dormant cell that is very resisitant to heat and cannot be destroyed easily, even by harsh chemicals, drying, or radiation.  A spore is composed of an exosporium (a thin protein covering), spore coat (layers of spore-specific proteins), cortex (loosely cross-linked peptidoglycan), and then the usual outer cell stuff.  Also on the inside of the cell there is Dipicolinic Acid, less water for less hydrolysis reactions, and a lot of SASP (Small Acid Soluble Protein) which makes the spore highly resistant to UV light.  A spore is different from a vegetative cell in that a vegetative cell is growing while a spore is dormant, a spore also has many outer coatings that the vegetative cell does not have, and the spore has less water inside along with a different internal composition.

3. What are the characterisitcs of spores that contribute to survivability?  Why?

Characteristics of spores that contribute to survivability are: an extremely tough outer layer, that protects the spore from heat and chemicals, an extremely dry inner composition, which prevents hydrolysis reactions from taking place and keeps the cell dormant, and SASP, which coats the DNA and protects it from UV light by producing spore photo product when struck with the radiation.

5. How is Bacillus anthracis similar to B. subtilis?

Both microorganisms are gram +, spore forming bacteria.

6. What properties of B. anthracis make it especially nasty?

What makes B. anthracis especially nasty is its three virulence factors encoded on two plasmids.

1. Capsule:  Prevents phagocytosis, made of polyglutamine, encoded on pX02 plasmid.
2. Toxins: Lethal toxin - first part is protective antigen, second part is a lethal factor which is a protease (enzyme that does damage). Edema toxin - first part is the protective antigen which binds to a cellular receptor, the second part is the edema factor which attacks adenylate cyclase.  These are encoded on the pX01 plasmid.

7. At the goat hair mill in Pennsylvania, workers were exposed to 510 spores per day, but didn't get antrax, why?

The immune system in the human body can handle a dose of 510 spores of anthrax.  It takes ~2500 spores to infect a person.

8. What are the steps of the disease after inhalation of B. anthracis?

Spores of B. anthracis are taken up by macrophages where they germinate and begin to multiply.  The multiplying B. antracis is then carried back to the local lymph node by the macrophage where the bacteria burst out.  B. anthracis then multiplies in the lymph node and spreads through the blood stream to the rest of the body.  The body continuously tries to fight off the B. anthracis infection by producing cytokines resulting in massive septic shock.

9. What are the virulence factors of B. anthracis, and how do they function?  Would these make good targets for antibiotics?  Vaccines?

The virulence factors for B. anthracis are its capsule and its two toxins.  The capsule is made of polyglutamine and it is encoded on the pX02 plasmid.  The capsule could be a good target for antibiotics to prevent the construction of since the capsule prevents phagocytosis.  A vaccine could also be used so that the body may recognize the capsule to facilitate phagocytosis.  There are 2 toxins that are made by B. anthracis and they are encoded on the pX01 plasmid.  These toxins are not necessary for the cell's survival so targeting them would do no good.

10. How does Anthrax Vaccine work?

People who get the anthrax vaccince are injected with a form of anthrax that is missing the capsule.  This way it is easier for the body to phagocytose the bacteria and make antigens for it.