Iris Maldener | The cell-cell communication system of filamentous cyanobacteria
Channel: CyanoWorld
Date: 2023-04-05

Iris Maldener - Eberhard Karl University of Tübingen, Germany

Homepage: https://uni-tuebingen.de/fakultaeten/mathematisch-naturwissenschaftliche-fakultaet/fachbereiche/interfakultaere-einrichtungen/imit/arbeitsgruppen/mikrobiologie-organismische-interaktionen/ag-maldener/
Research Gate: https://www.researchgate.net/profile/Iris-Maldener

The cell-cell communication system of filamentous cyanobacteria

Multicellular organisms require controlled intercellular communication for their survival. We demonstrated that the filamentous cyanobacterium Anabaena (Nostoc) PCC 7120 regulates cell-cell communication between sister cells via a conformational change in septal junctions (SJs).

We revealed the in situ architecture of SJs by imaging focused ion beam-thinned filaments with cryoelectron tomography. The SJs consist of a septum-spanning tube with a membrane-embedded plug at both ends, and a cap covering the plug on the cytoplasmic side.

Under stress conditions, the SJs close by conformational change abolishing intercellular exchange, which can be measured using fluorescent marker molecules in FRAP (fluorescence recovery after photobleaching) measurements. This process is reversible, which renders SJs gated cell-cell connections.

The impact of the cap and plug module on SJ closure was demonstrated by investigating a fraD-mutant, which lacked both modules and was unable to abolish communication when exposed to stress conditions We also showed that the FraD protein is a structural SJ component, which localizes to the plug domain.

Via co-immunoprecipitation, we identified another SJ protein, SepN, and showed its localization in the septa, where it is essential for proper SJ assembly. A sepN-mutant exhibited a highly reduced rate of intercellular communication and lost the ability of SJ gating. The SJs lacked the plug module and displayed an aberrant cap.

Since the mutants in SJ components display reduced filament survival after stress, we propose that controlling molecular diffusion between cells is important for the survival of these multicellular bacteria.

This talk is part of the CyanoWorld online seminar series, hosted by Nicolas Schmelling and Ilka Axmann, and was held on Zoom on February 9th, 2023.

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