RT Journal Article SR Electronic T1 A cytoskeletal network maintains filament shape in the multicellular cyanobacterium Anabaena sp. PCC 7120 JF bioRxiv FD Cold Spring Harbor Laboratory SP 553073 DO 10.1101/553073 A1 Benjamin L. Springstein A1 Dennis J. Nürnberg A1 Ann-Katrin Kieninger A1 Christian Woehle A1 Julia Weissenbach A1 Marius L. Theune A1 Andreas O. Helbig A1 Andreas Tholey A1 Iris Maldener A1 Tal Dagan A1 Karina Stucken YR 2019 UL http://biorxiv.org/content/early/2019/05/24/553073.abstract AB The determinants of bacterial cell shape are extensively studied in unicellular forms. Nonetheless, the mechanisms that shape bacterial multicellular forms remain understudied. Here we study coiled-coil rich proteins (CCRPs) in the multicellular cyanobacterium Anabaena sp. PCC 7120 (hereafter Anabaena). Our results reveal two CCPRs, termed LfiA and LfiB (for linear filament), which assemble into a heteropolymer that traverses the longitudinal cell axis. Two additional CCRPs, CypS (for cyanobacterial polar scaffold) and CeaR (for cyanobacterial elongasome activity regulator), form a polar proteinaceous scaffold and regulate MreB activity, respectively. Deletion mutants of these CCRPs are characterized by impaired filament shape and decreased viability. Our results indicate that the four CCRPs form a proteinaceous network that stabilizes the Anabaena multicellular filament. We propose that this cytoskeletal network is essential for the manifestation of the linear filament phenotype in Anabaena.