[S2-3] Direct observation of proliferation of cell wall-deficient Escherichia coli cells
Most of bacterial cells are surrounded by cell wall, or peptidoglycan layer, which prevents cells from lysis by turgor pressure. Thus, if bacterial cells are treated with antibiotics such as penicillin which inhibits peptidoglycan synthesis, cells are lysed. It is known that some cells in the population are viable by converting to a cell wall-deficient state, called L-form, even in the presence of antibiotics. Cell division of L-form seems not to be tightly regulated because FtsZ, an essential protein for division of walled cells, is not required for cell division of L-form. Therefore, division of L-form is considered as a model system for that of primitive cells. We confirmed that FtsZ-depleted cells converted to L-form and grew well as WT L-form cells. We found that Z ring was retained in L-form cells after the conversion to L-form from walled state but cells were divided independently of Z ring. If division is not well-regulated, then, how is genomic DNA segregated in L-form? We visualized genomic DNA by HupA-GFP and found that L-form is divided between two nucleoids, suggesting that nucleoid occlusion is still functional in L-form cells. We also observed subcellular localization of ori and ter regions in L-form. We will discuss proliferation and DNA segregation of L-form and primitive cells.