Lipid domains in Bacillus subtilis anucleate cells

Bacterial membranes are known to form domains with specific lipid compositions and functions. Recently, using membrane binding fluorescent dyes, lipid spiral structures extending along the long axis of the cell were detected. These spirals were absent when the synthesis of phosphatidylglycerol and cardiolipin was disrupted, suggesting that the spirals are enriched in anionic phospholipids. It was also shown that the cardiolipin-specific NAO dye is preferentially distributed at the cell poles and in the septal regions. These results suggest that phoshatidylglycerol may be the principal component of the observed spiral domains. Additionally, GFP fusions of the cell division protein MinD also form spiral structures which are coincident with the lipid spirals, indicating their involvement in cell division. Here, using fluorescent dyes FM4-64 and NAO, we demonstrate the existence of lipid domains in Bacillus subtilis cells with inhibited DNA replication. The lipid domains observed are similar to those in the wild type, indicating that either formation of these domains is not affected by inhibition of replication or that structures already established are relatively stable. The results further suggest that the GFP-MinD spirals exist in these strains as well.