TABLE 2.

Single cell comparison of SOS induction, phage expression (PBSX), and formation of RecA-GFP foci after exposure to DNA damage in B. subtilis^a

Treatment	% of cells with fluorescence or foci (n)
	RecA-GFP	XkdF-YFP (PBSX)	TagC-GFP (SOS)
Untreated	10 (447)	0.05 (2,006)	0.06 (3,125)b
I-SceI uninduced	19 (515)	0.2 (1,050)	1.9 (1,952)
I-SceI repressed	16 (442)	0.15 (1,348)	0.5 (1,808)
I-SceI expressed	75 (424)	1.4 (789)	4.6 (829)
100 Gy	98 (437)	0.4 (1,851)	0.3 (1,704)
MMC (1 μg/ml)	>99 (1,738)	19 (776)	99 (874)

^aFor the untreated samples and the 100-Gy-treated and MMC-treated strains, PY79 bears the indicated fusion (RecA-GFP, XkdF-YFP, or TagC-GFP) but is otherwise a wild-type strain and does not encode the I-SceI endonuclease or the I-SceI recognition site. These strains were grown in S7₅₀ minimal medium supplemented with glucose, tryptophan, and phenylalanine. I-SceI uninduced cells were grown in S7₅₀ with arabinose as a carbon source. For repressed conditions the cells were grown in S7₅₀ with glucose, and under expressed conditions cells were grown in S7₅₀ with arabinose followed by the addition of 0.2% xylose to induce expression of the I-SceI endonuclease. Cells treated with ionizing radiation (100 Gy) were grown in S7₅₀ minimal medium supplemented with 1% glucose, tryptophan, and phenylalanine. The data presented in this table are from at least two independent experiments. The number of cells scored (n) is indicated in parentheses for each condition.

^bFluorescence was observed for only two cells. The fluorescence intensity was weak compared to the fluorescence intensity after exposure to 1 μg of MMC/ml.