Deletion of the spf (spot 42 RNA) gene of Escherichia coli.

To investigate the function of spot 42 RNA, a small RNA of Escherichia coli, we constructed a strain in which spf, the structural gene for this RNA, is deleted. We achieved this by using a delta att phage lambda carrying a DNA fragment spanning the spf region but with a precise deletion of spf. By integration of this phage at the spf locus and by its subsequent excision, we were able to cross the spf deletion onto the bacterial chromosome. The fact that such a deletion could be obtained indicated that spf is not an essential gene. We did not observe any major defect in delta spf cells, although in one strain background the deletion caused a slight growth impairment.