The ribosome-binding GTPase HflX is required for manganese homeostasis in E. coli. While under normal conditionsDhflX cells behave like wild type E. coli with respect to growth pattern and morphology, deletion of hflX makes E. coli cellsextremely sensitive to manganese, characterized by arrested cell growth and filamentation. Here we demonstrate that uponcomplementation by hflX, manganese stress is relieved. In phenotypic studies done in a manganese-rich environment, DhflXcells were highly sensitive to antibiotics that bind the penicillin binding protein 3 (PBP3), suggesting that the manganesestress led to impaired peptidoglycan biosynthesis. An irregular distribution of dark bands of constriction along filaments,delocalization of the dark bands from midcell towards poles and subpoles, lack of septum formation and arrested celldivision were observed in DhflX cells under manganese stress. However, chromosome replication and segregation ofnucleoids were unaffected under these conditions, as observed from confocal microscopy imaging and FACS studies. Weconclude that absence of HflX leads to manganese accumulation in E. coli cells, affecting cell septum formation, probablyby modulating the activity of the cell division protein PBP3 (FtsI), a major component of the divisome apparatus. Wepropose that HflX acts as a gatekeeper, regulating the influx of manganese into the cell.
Volume 45, 2020
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