I remember on some show that I watched years ago (but I can't recall which show it was) they were kind of getting into this area. One of the things they were saying is that the DNA of all life on this planet spirals in the same direction and that if we ran into alien life whos DNA spirals in the opposite direction that the germs from each wouldn't infect the other.

Didn't that supposed reply crop circle to the Arecibo message say that the aliens who sent it are silicone and carbon based?
Can silicone and carbon combined? What would it be like for us to encounter their germs?

I remember NASA quarantining the Apollo astronauts when they came back from the moon because they were worried about the possibility of alien germs. Was that just for the early missions or for all of them?

 

How important will biomass be for extended space flights and other planetary visits and stays?
Biomass will be what microbial soup comes from.