I understand the whole ulcers in one environment idea, making the H. pylori bacterium identifiable. could be that Crohn's isn't one organism. doctors can't even positively say if you have Crohn's. our GI specialist said that my son "has symptoms consistent with Crohn's. they can only identify symptoms. if you have cancer, they can find cancer cells. if you have a cold, the flu, herpes, HIV, strep, anything other than auto-immune conditions, they can definatively point to the organism involved.
maybe, more than one organism causes "symptoms consistent with Crohn's." maybe the barrier to finding the cause is because it is "causes". as for organisms being relagated to one environment, look outside the world of crohn's. butterflies have been found on top of mountains, and deep within rainforests. humans now enhabit every continent on the planet. just a thought, but maybe the causal organism adapts.