Liu Jing, Xing Wei-Yue, Zhang Ju-Yuan, Zeng Xiaoli, Yang Yiling, Zhang Cheng-Cai
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China.
College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China.
Front Microbiol. 2021 Oct 21;12:765878. doi: 10.3389/fmicb.2021.765878. eCollection 2021.
Bacterial cell shape is determined by the peptidoglycan (PG) layer. The cyanobacterium sp. PCC 7120 () is a filamentous strain with ovoid-shaped cells connected together with incomplete cell constriction. When deprived of combined nitrogen in the growth medium, about 5-10% of the cells differentiate into heterocysts, cells devoted to nitrogen fixation. It has been shown that PG synthesis is modulated during heterocyst development and some penicillin-binding proteins (PBPs) participating in PG synthesis are required for heterocyst morphogenesis or functioning. has multiple PBPs with functional redundancy. In this study, in order to examine the function of PG synthesis and its relationship with heterocyst development, we created a conditional mutant of , a gene necessary for the synthesis of the PG precursor, lipid I. We show that is required for cell and filament integrity. Furthermore, when expression was being limited, persistent septal PG synthetic activity was observed, resulting in increase in cell width. Under non-permissive conditions, filaments and cells were rapidly lysed, and no sign of heterocyst development within the time window allowed was detected after nitrogen starvation. When expression was being limited, a high percentage of heterocyst doublets were found. These doublets are formed likely as a consequence of delayed cell division and persistent septal PG synthesis. MraY interacts with components of both the elongasome and the divisome, in particular those directly involved in PG synthesis, including HetF, which is required for both cell division and heterocyst formation.
细菌的细胞形状由肽聚糖（PG）层决定。蓝藻菌株集胞藻PCC 7120（）是一种丝状菌株，其卵形细胞通过不完全的细胞缢缩连接在一起。当生长培养基中缺乏化合态氮时，约5-10%的细胞会分化为异形胞，即专门用于固氮的细胞。研究表明，在异形胞发育过程中PG合成受到调控，参与PG合成的一些青霉素结合蛋白（PBPs）是异形胞形态发生或功能所必需的。集胞藻PCC 7120有多个具有功能冗余的PBPs。在本研究中，为了研究PG合成的功能及其与异形胞发育的关系，我们构建了集胞藻PCC 7120的一个条件突变体，该突变体缺失PG前体脂质I合成所必需的基因。我们发现该基因对于细胞和丝状体的完整性是必需的。此外，当该基因的表达受到限制时，会观察到持续的隔膜PG合成活性，导致细胞宽度增加。在非允许条件下，丝状体和细胞会迅速裂解，并且在氮饥饿后的允许时间窗口内未检测到异形胞发育的迹象。当该基因的表达受到限制时，会发现高比例的异形胞双联体。这些双联体的形成可能是细胞分裂延迟和持续的隔膜PG合成的结果。MraY与延伸体和分裂体的成分相互作用，特别是那些直接参与PG合成的成分，包括细胞分裂和异形胞形成都需要的HetF。
