Identification of a Single Strand Origin of Replication in the Integrative and Conjugative Element ICEBs1 of Bacillus subtilis
Fig 3
Visualization of Sso function in living cells.
All cells expressed Ssb-GFP, which binds to ssDNA. Top and bottom panels are images from differential interference contrast (DIC) and fluorescence microscopy, respectively. Representative images are shown. (A) no plasmid, strain CMJ118. The small foci of Ssb-GFP are likely located at the replication forks [40]. One focus of Ssb-GFP is indicated with an arrow. (B) pHP13 (no sso), strain CMJ129. Large foci of Ssb-GFP foci were observed in cells that contain pHP13, a plasmid that replicates by a rolling circle mechanism but does not contain an sso. An arrowhead marks one large focus, indicating that Ssb-GFP likely bound to pHP13 ssDNA. (C) pHP13sso1, strain CMJ130. Cells containing pHP13sso1 did not have as many large foci of Ssb-GFP as those in panel B. An arrow indicates a small focus similar to those observed in cells with no plasmid (panel A). (D) pHP13sso1R, strain CMJ131. Cells containing pHP13 with ICEBs1 sso1 cloned in the reverse orientation had large foci of Ssb-GFP, indicating the accumulation of ssDNA. An arrowhead highlights a large focus, similar to the large foci observed in cells with pHP13 (no sso) (panel B).