Stationary phase in Trypanosoma cruzi epimastigotes as a preadaptive stage for metacyclogenesis

Trypanosoma cruzi is a species of parasitic protozoa that causes American trypanosomiasis or Chagas disease. These parasites go through a complex life cycle in Triatominae insects and vertebrate hosts. Epimastigotes are replicative forms that colonize the digestive tract of the vector and can be cultured in axenic media. The growth curve of epimastigotes allows assessment of differences in cells undergoing growth rate transitions from an exponential growth to a stationary phase. Since the classical descriptions of T. cruzi, it has been noted that the growth curve of epimastigotes in culture can give rise, in the stationary phase, to nonreplicating forms of metacyclic trypomastigotes. Metacyclogenesis therefore regards to the development process by which epimastigote transform into infective metacyclic trypomastigotes. In nature, these metacyclic forms allow the spread of Chagas disease when transmitted from an infected vector to a vertebrate host. This work reviews cellular phenomena that occur during the growth rate transitions of epimastigotes in culture, which may be related to very early physiological conditions for metacyclogenesis. Many of these events have not been thoroughly investigated. Their analysis can stimulate new hypotheses and future research in an important area not fully exploited.