Each bacterial species has its specific cell size and shape. How do bacteria maintain their morphological homeostasis? We use the multicellular filamentous cyanobacterium Anabaena PCC 7120 as a model to investigate this classical and important scientific question in microbiology. This cyanobacterium is particularly interesting because it can also differentiate a particular cell type, heterocyst, for nitrogen fixation, so that oxygen-evolving photosynthesis and oxygen-sensitive nitrogen fixation can occur at the same time (1). Using approaches from molecular genetics to cell biology and structural biology, we found that cell division, differentiation and cell size control are intimately linked (1-4). I’ll present our recent study demonstrating that cell division acts as a checkpoint for heterocyst development. In addition, we also show that the signalling pathway of the ubiquitous bacterial second messenger c-di-GMP is involved in cell morphological control (4). Cyanobacteria are increasingly used for research in synthetic biology, and some of them can also form environmentally harmful blooms. Our basic understanding on the biology of cyanobacteria will provide insight in the applied research areas of cyanobacteria.
1) Zeng X. and Zhang C-C. (2022) The making of a heterocyst. Annu. Rev Microbiol. 76 :597-618.
2) Xing W-Y. et al. (2022) A proteolytic pathway coordinates cell division and heterocyst differentiation in the cyanobacterium Anabaena sp. PCC 7120. PNAS 119:e2207963119.
3) Liu J. et al. (2023) Three-dimensional coordination of cell-division site positioning in a filamentous cyanobacterium. PNAS Nexus 2 :pgac307.
4) Zeng X. et al. (2023) A c-di-GMP binding effector controls cell size in a cyanobacterium. PNAS, 120 :e2221874120.