TABLE 1.

Overexpression of CcCnoX complements a Cctrx1 deletion

Strain	% of deletion mutants obtained witha :
	WT	Low-copy plasmid		High-copy plasmid
		p-Cctrx1	p-CccnoX	p-Cctrx1	p-CccnoX
ΔCctrx1::tet mutant	0	48	4	54	42

^aThis table shows that Cctrx1 can only be deleted in the presence of an exogenous copy of Cctrx1 or when CcCnoX is overexpressed. Low expression of CcCnoX is not sufficient to complement a Cctrx1 knockout. The two-step recombination method used to produce knockouts in C. crescentus leads to the production of 50% deletion mutant and 50% wild-type clones when the gene deleted is not essential. The numbers in the table indicate the percentage of deletion mutants obtained under each tested condition.