Sentence:  It is likely that the long evolutionary trajectory of "Mycoplasma" went from a <WSD>reductive</WSD> autotroph to oxidative heterotroph to a cell-wall–defective degenerate parasite. This evolutionary trajectory assumes the simplicity to complexity route of biogenesis, a point of view that is not universally accepted. 
Meaning of the word marked with <WSD> tags:  That reduces a substance etc. to a more simple or basic form. (from 17th c.)