Roger de Groot wrote in message <72vcba$mo8$1 at heracles.fw.cuci.nl>...
>Why is it only possible to grow Treponema pallidum in suitable tissue?
>>Thanks Roger de Groot
Because we don't know exactly what its nutritional requirements are. If we
(a) knew and (b) could provide them without tissue (or animal culture) then
we could grow them in conventional microbial systems.