FIG. 4.

Fluorescence micrographs showing filamentation in a ponA mutant (strain PS2062) grown at 30°C in 2× YT medium. (A and B) ponA mutant cells; (C) wild-type cells. (Ai, Bi, and Ci) DAPI staining of nucleoids (blue); (Aii, Bii, and Cii) staining of cell walls and septa with Oregon green-conjugated WGA (green); (Aiii, Biii, and Ciii) overlay of DAPI staining and cell wall staining. Bar, 10 μm. Arrows in panels Aii and Aiii show a bright green dot in the periphery of ponA mutant cells between two nucleoids (arrow in Ai). Such dots were seen in 39% of the ponA mutant cells examined (n = 163) but were not seen in wild-type cells (0%; n = 137). Similar results were obtained when cells were grown in 2× YT medium at 37°C (39% of the ponA mutant cells had dots [n = 222]; 0% of wild-type cells had dots [n = 339]).