Bacterial cell Structure
The prokaryotic tubulin homolog protein FtsZ assembles into the Z-ring at mid-cell to provide contractile force during bacterial cell division. Here, by tracing the status of FtsZ in living E. coli cells, we unexpectedly revealed a cytosolic organelle-like structure containing the FtsZ protein that is solely formed in non-growing/non-dividing late stationary-phase cells and is located at the cell poles. This structure, which we named the quiescent body, contains selected essential proteins involved in cell growth and division, and its formation depends on the operation of the cellular respiratory chain. The quiescent bodies start to disassemble to release the important proteins that will resume functioning upon cell re-growth/re-division under permissive growth conditions, while those cells containing intact quiescent bodies do not re-grow/re-divide. Meanwhile, the quiescent bodies endow the cells with a higher antibiotic resistance capacity by inhibiting cell recovery. Our discoveries reported here strongly suggest that the quiescent bodies sequester proteins important for cell growth/division and thus maintain the cells in a quiescent state. These findings also implicate that bacterial pathogens might be effectively killed by antibiotics that only target growing cells by blocking the assembly or promoting the disassembly of quiescent bodies.