TABLE 2 .

Confirmation of σ²²-dependent gene expression during cell wall stress for selected promoters

Promoter-lacZ fusiona	Fold increase in β-galactosidase activity due to d-cycloserine treatment
	PAO1	algT
PA0567-lacZ	2.3	10.9
PA0920-lacZ	5.6	2.6
PA2177-lacZ	14.2	2.3
PA3040-lacZ	10.0	2.2
PA3459-lacZ	9.0	2.4
PA3795-lacZ	11.4	3.3
PA4717-lacZ	8.8	2.8
PA5424-lacZ	19.2	1.7

^a Listed are promoter-lacZ fusions from Table 1 that did not yield the predicted phenotypes under unstressed conditions in algT and/or mucA mutant backgrounds. Here they were compared for β-galactosidase activity under cell wall stress conditions in PAO1 and an algT mutant by exposure to d-cycloserine. Bacteria were grown under routine lab conditions (L broth with aeration at 37°C) to an OD₆₀₀ of 0.3 and treated with a sub-MIC level (400 µg/ml) of d-cycloserine for 60 min. The fold increase in β-galactosidase activity (Miller units) shown is a comparison to that of untreated control cultures. In PAO1 containing functional σ²², all 8 promoter fusions above showed an increase in transcriptional activity when exposed to d-cycloserine. None of these promoters, except PA0567-lacZ, showed high induction in the σ²² knockout, PAO1algT, indicating their dependence on σ²² for increased expression during cell wall stress.