> but there is no
 > way a single bacteria species can replace all the various bugs that are
 > supposed to live in the gut. I probably should try dirt eating... ;-)

try to eat some meats very aged and raw .The b12 deficiency is also
suspected to be of autoimmune nature , if it is the case no supplemts will
do its job only a radical change of diet might bring back a healthy gut
flora .
to give you a macroscopic  analogy .think of the gut as an ecosytem ,
playing god by deciding which animals or plants are supposed to be
introduced or eradicated in that ecosystem can only lead to further
unbalances .
jean-claude