Following grows in the cell free medium except -a) Rickettsiab) M lepraec) Bartonellad) Syphilis

Obligate intracellular organisms To grow in a medium which does not contain cells (cell free medium), organism should be capable of ATP synthesis. Obligate intracellular organisms are not capable of the metabolic pathways for ATP synthesis. So, these organisms are dependent on the ATP of host cells. As they require host cell ATP, they can not grow in the media which do not contain cells (cell free media). Such organisms are - Rickettsiae Chlamydiae  Viruses                                                              M.leprae Pathogenic treponemes (syphillis)