Fig. 2.

Ax21 and the nonsulfatable Y22A variant form of Ax21 (here designated AX21Y) are active in regulation and as extracellular signals in S. maltophilia. (A) Exogenous addition of synthetic Ax21 protein (AX21) to the medium restored motility to an ax21 mutant but not to raxH (sensor kinase) or raxR (regulator) mutants. (B) Exogenous addition of synthetic Ax21 protein to an ax21 mutant restored the levels of expression of smlt1112, smlt1390, smlt2175, and smlt3949 toward those of the wild type as measured by qRT-PCR. This effect was not seen in the raxH (sensor kinase) mutant. (C) Addition of AX21Y to the medium or in trans expression of the AX21Y variant from p0387Y22A restored motility to an ax21 mutant. (D) Addition of AX21Y to an ax21 mutant restored the levels of expression of smlt1112, smlt1390, smlt2175, and smlt3949 toward wild-type levels as measured by qRT-PCR. This effect was not seen in the raxH (sensor kinase) mutant.