TABLE 2.

Permeability of E. coli strains expressing different levels of Hda protein as indicated by the fluorescent dye SYTOX Green^a

Strain	Induced with IPTG	% of fluorescent nucleoids
1921	+	40
	−	0
1110	+	4
	−	0

^aAfter strains 1921 and 1110 were grown to mid-logarithmic phase, 0.3 mM IPTG was added to cultures and incubated an additional 3 h. A loopful of each culture was spread on a glass slide, heat fixed, stained with SYTOX Green (using methods recommended by the manufacturer, Molecular Probes), counterstained with methyl green, and visualized by fluorescence microscopy, using a Zeiss LSM 510 microscope with a 488-nm argon laser. Images were captured using Zeiss LSM 510 software and a Zeiss C-Apochromat 63× objective. Between 6 and 10 microscopic fields were examined for the percentage of cells containing fluorescent nucleoids. +, cultures with IPTG; −, cultures without IPTG.