Fig. 6.

Insertion sequences in the E. coli ompR-envZ promoter govern resistance to ammonia. a (left) spontaneous suppressor mutant ARM9 derived from E. coli strain ASD19 growing under the presence of volatile compounds produced by Streptomyces sp. MBT11; (right) visualization of insertion sequences in-between the −10 and −35 sequences of the ompR/envZ promoter. b Growth of E. coli strain ASD19 (black) and E. coli strain ASD19 suppressor mutant ARM9 (gray) under the presence of different concentrations of ammonia. c Growth of suppressor mutant ARM9 and transformants harboring either empty plasmid pCA24N, plasmid ompR-pCA24N (expressing ompR), or plasmid envZ-pCA24N (expressing envZ). Note that introduction of a plasmid expressing either envZ or ompR makes ARM9 sensitive again to ammonia