Abstract
Cell division in bacteria has been studied mostly in Escherichia coli and Bacillus subtilis, model organisms for Gram-negative and Gram-positive bacteria, respectively. However, cell division in filamentous cyanobacteria is poorly understood. Here, we identified a novel protein, named CyDiv (Cyanobacterial Division), encoded by the all2320 gene in Anabaena sp. PCC 7120. We show that CyDiv plays a key role during cell division. CyDiv has been previously described only as an exclusive and conserved hypothetical protein in filamentous cyanobacteria. Using polyclonal antibodies against CyDiv, we showed that it localizes at different positions depending on cell division timing: poles, septum, in both daughter cells, but also in only one of the daughter cells. The partial deletion of CyDiv gene generates partial defects in cell division, including severe membrane instability and anomalous septum localization during late division. The inability to complete knock out CyDiv strains suggests that it is an essential gene. In silico structural protein analyses and our experimental results suggest that CyDiv is an FtsB/DivIC-like protein, and could therefore, be part of an essential late divisome complex in Anabaena sp. PCC 7120.
Highlights
Cyanobacteria are unique microorganisms that have been major determinants of the evolution of life on Earth as they converted our planet’s reducing atmosphere into an oxidizing one by being the initiators of oxygenic photosynthesis (Cavalier-Smith, 2010)
We found that the pattern of CyDiv localization correlates with cell division state
FtsB and DivIC belong to the subcomplexes FtsQ-FtsL-FtsB and DivIB-FtsL-DivIC, which are involved in the late recruitment of proteins of the divisome in E. coli and B. subtilis respectively, including proteins required for cell wall synthesis (Katis et al, 1997; Buddelmeijer and Beckwith, 2004; Harry et al, 2006)
Summary
Cyanobacteria are unique microorganisms that have been major determinants of the evolution of life on Earth as they converted our planet’s reducing atmosphere into an oxidizing one by being the initiators of oxygenic photosynthesis (Cavalier-Smith, 2010). Cyanobacteria are divided into five subsections depending on their morphologies, where I and II include unicellular coccoids and III to V involve filamentous forms. Filamentous cyanobacteria from sub-sections IV and V are considered true multicellular microorganisms because some cells in a filament can differentiate into specialized forms (Rippka et al, 1979). Unlike unicellular forms, filamentous cyanobacterial cells remain connected even after cell division is completed and the outer membrane is continuous along the filament. Cell communication and filament maintenance is mediated by a continuous
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