New Paper: Chlamydiae give up extracellular stage to thrive in social amoebae
Many intracellular bacteria rely on an extracellular stage to move between hosts – but what happens when that’s no longer needed? A new study, now published in Current Biology, reveals a striking example: A chlamydial symbiont of the social amoeba Dictyostelium giganteum has lost its extracellular form entirely and spreads only when host cells aggregate and interact with each other.
A team around Lukas Helmlinger and Matthias Horn from CeMESS studied the imprint of the amoebae’s social life cycle on the chlamydial symbiont in detail. Known chlamydiae are characterized by a developmental cycle alternating between an intracellular replicative form and an infectious extracellular form that survives outside and can infect new host cells. The loss of the extracellular form marks a major evolutionary transition and suggests an exceptionally intimate host-symbiont relationship between the symbiont and its unicellular host, whose social life cycle includes aggregation of thousands of cells and the formation of multicellular fruiting bodies.
The findings shed new light on microbial adaptation to facultative multicellularity and offer a valuable model for studying the evolution of endosymbiosis and host adaptation.
