Bacillus anthracis: Vegetation, spore stage, and phagocytosis

[Genecks]

Something I don't understand about Bacillus anthracis is its ability to become vegatative inside of a host system and survive. I sometimes read articles that describe it having a capsule. As I understand, capsules often prevent the microorganism from being consumed by macrophages. At other times, it seems like I am reading that spores are moving through the body and don't vegetate until they are inside an environment, such as a macrophage.

 

In the B. anthracis strains carrying plasmid pXO2, capsule synthesis by vegetative cells was activated within macrophages that promoted a rapid escape of the vegetative cells from the macrophages.

link

 

Is that realistic? For a B. anthracis spore to move around the body and then only vegetate once it's inside of a macrophage?

 

I guess that's what research says.

 

Is it during the spore stage that an immunological response occurs, thus triggering macrophages to consume the invader?

 

But I believe I also read about macrophages still able to phagocytise vegetative states of B. anthracis with the capsule. Is that normal behavior of a macrophage? For what I understand, macrophages typically have trouble doing that.

[Callie]

Im going off on a bit of a tangent, I know but did you hear about the chap who caught anthrax from animals hides in London last month? scary!

[Genecks]

I read about that: link

 

I also read about the recent (08/2008) suicide of the person accused of the bioterrorist actions on the U.S. senate building: link

 

But besides these things, can anyone offer information to my thread?

[CharonY]

Edit: I am writing up garbage at the moment.

 

In any case, it is not that necessarily so that B. anthracis [\I] only germinates in macrophages.

Other factors might also trigger germination. Generally bacterial spores react to presence of nutrient, quorum sensing cues, or certain ions, though I am not sure which cues from the host cell are actually triggering B. anthracis germination (there is literature about them available, I just have not read them). As such I am not currently aware if the same germination stimuli can also be triggered by other cells that may have phagocytosed B. anthracis spores. On the other hand, macrophages tend to be the first actually encountering them, thus the bulk (if not all) of research has been focussed on this particular way of infection. Given the fact that the way of entry of the spores does have an impact on the virulence, it is is likely that germination via macrophages is the primary route (at least from the viewpoint of a disease onset).

Also, normally infections do not occur with vegetative cells, but with endospores thus entry of vegetative B. anthracis cells is rather unlikely and does not cause diseases. In other words, for the disease the the bacterium indeed enters the body as a spore and has to germinate before actually causing any damage.

Edited November 3, 2008 by CharonY
multiple post merged