Abstract
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.
Footnotes
↵† Institute of Experimental Physics, Free University of Berlin, Berlin, Germany
↵¥ Max Planck Institute for Plant Breeding Research, Max Planck-Genome-center Cologne, Cologne, Germany
↵‡ Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel
The text has been adapted to a longer article format and a few more quantitative data as well additions on the functionality of the protein fusions were included.