Table 1.

Effect of multicopy greA, greB, and dksA genes on growth of the ppGpp⁺ (spoT⁺relA⁺ or spoT⁺ ΔrelA) strains

Row no.	Strain descriptionb	Plasmid	Growth on M9 platesa
			− IPTG	+ IPTG
1	Wild type (± greB)	Vectorc	+	+
2		pGreA	+	+ (≪)
3		pGreB	+	+ (<)
4		pDksA	+	+ (≪)
5	dksA (± greB)	Vector	+	+
6		pGreA	+	+ (>)
7		pGreB	+	+ (≫)
8		pDksA	+	+ (≪)
9	greA (± greB)	Vector	+	+
10		pGreA	+	+
11		pGreB	+	+
12		pDksA	+	+ (≪)
13	dksA greA (± greB)	Vector	−	−
14		pGreA	+	+ (>)
15		pGreB	+	+ (≫)
16		pDksA	+	+ (≪)

^aStrains grown in LB medium supplemented with 50 μg/ml spectinomycin were diluted in 10 mM Mg₂SO₄ prior to plating on LB or M9 glucose minimal plates with (+) or without (−) 0.1 mM IPTG. Colony diameters were measured after 3-day incubations at 37°C on plates containing less than 100 colonies. +, the strain formed colonies; −, less than 1% of colonies were present compared to plating of the same dilution on LB medium. Symbols between parentheses denote colony diameters on IPTG-containing plates that were smaller (< and ≪) or larger (> and ≫) than the diameter of the colonies formed by the same strain on plates not supplemented with IPTG.

^brelA⁺ and ΔrelA strains yielded similar results. ± greB, similar results were obtained in the presence or absence of the greB gene.

^cThe vector control was pHM1883.