Structure of a thylakoid-anchored contractile injection system in multicellular cyanobacteria.

Gregor L Weiss, Fabian Eisenstein, Ann-Katrin Kieninger, Jingwei Xu, Hannah A Minas, Milena Gerber, Miki Feldmüller, Iris Maldener, Karl Forchhammer, Martin Pilhofer

Nature microbiology 2022 Mar

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Contractile injection systems (CISs) mediate cell-cell interactions by phage tail-like structures, using two distinct modes of action: extracellular CISs are released into the medium, while type 6 secretion systems (T6SSs) are attached to the cytoplasmic membrane and function upon cell-cell contact. Here, we characterized a CIS in the multicellular cyanobacterium Anabaena, with features distinct from extracellular CISs and T6SSs. Cryo-electron tomography of focused ion beam-milled cells revealed that CISs were anchored in thylakoid membrane stacks, facing the cell periphery. Single particle cryo-electron microscopy showed that this unique in situ localization was mediated by extensions of tail fibre and baseplate components. On stress, cyanobacteria induced the formation of ghost cells, presenting thylakoid-anchored CISs to the environment. Functional assays suggest that these CISs may mediate ghost cell formation and/or interactions of ghost cells with other organisms. Collectively, these data provide a framework for understanding the evolutionary re-engineering of CISs and potential roles of these CISs in cyanobacterial programmed cell death. © 2022. The Author(s).

Citation

Gregor L Weiss, Fabian Eisenstein, Ann-Katrin Kieninger, Jingwei Xu, Hannah A Minas, Milena Gerber, Miki Feldmüller, Iris Maldener, Karl Forchhammer, Martin Pilhofer. Structure of a thylakoid-anchored contractile injection system in multicellular cyanobacteria. Nature microbiology. 2022 Mar;7(3):386-396