Congratulations, Dr. Helmlinger!
Lukas Helmlinger successfully defended his PhD thesis on May 04, 2026.
Symbiosis shapes major evolutionary transitions. In his thesis, Lukas investigates how chlamydiae adapt to social, multicellular stages in their protist hosts, the dictyostelids. He analyzes chlamydial symbionts from eight dictyostelid isolates using genome sequencing, microscopy, and digital PCR. The symbionts show extensive, lineage-specific gene loss—particularly of regulators of the classic chlamydial developmental cycle—together with loss of typical morphological stages and an absence of extracellular forms. The chlamydiae spread efficiently within hosts both vertically during the social life cycle and horizontally via cell-to-cell contact, yet cause little to no detectable harm to host fitness. Taken together, the thesis describes a shift toward a host-adapted lifestyle driven by gene loss and altered transmission modes, offering new insights into chlamydial evolution and endosymbiosis.
CeMESS\Kerrin Steensen