TABLE 2.

Survival after alkaline and salt shock at stationary phase

Row	Plasmida	Survival (%)b
		NaCl (mM)				KCl (400 mM)
		0	200	400	600
1	pBR322	0.13	0.014	5 × 10−5	0	0.065
2	pGM42	100	61	44	14	100
3	pGM36*	100	56	35	8	56
4	pBR322	100	43.6	29.3	11.1	100
5	pGM42	100	90	80	69.5	83
6	pGM36*	100	100	100	100	100

^aOR200 (ΔnhaA ΔnhaB) bacteria carrying the indicated plasmid were grown overnight (OD₆₀₀ = 3 to 4) in LBK medium at 37°C and attained a pH value of 8. Rows 1 to 3, the cultures were shifted to pH 9.5 by titration with KOH with or without addition of the indicated salts and incubated for 3 h at 37°C. Rows 4 to 6, the same procedure as for rows 1 to 3 but without the pH shift. 

^bThe number of CFU was determined, and survival is expressed as a percentage of that for the control.