FIG 4.

Altered expression of several diguanylate cyclase genes, and of yhjH, in the hns mutant. (A) Upregulation of diguanylate cyclase genes, and downregulation of yhjH, in the FlhDC-constitutive Δhns ΔflhDC mutant. The strain used was EK2 transformed with plasmid pKP148 as a source of FlhDC, with induction with 100 μM IPTG. Transcript levels were determined by the 2^−ΔΔCT method and are relative to the levels in the strain complemented with wild-type hns on a plasmid (pKP58 induced with 10 μM salicylate). Values are the means of data from 3 independent experiments (±standard deviations), each representing an average of results based on three reference genes (rpoD, hisG, and cysG), as described in Materials and Methods. (B) Motility inhibition upon overexpression of the diguanylate cyclase YeaJ. The strain used was EK2 transformed with pKP148 to provide FlhDC (with induction with 100 μM IPTG) and with either plasmid pEK25 expressing yeaJ under salicylate control (p-yeaJ) or the parent vector pKG116 (vect). Results are shown for three levels of induction by salicylate. Plates were inoculated with 3-μl drops from cultures grown overnight and incubated at 32°C for 8.5 h.