Pseudomonas aeruginosa β-lactamase induction requires two permeases, AmpG and AmpP

BMC Microbiology

Table 1 β-lactamase activity of P. aeruginosa PAO1, PAOampG and PAOampP in the absence and presence of β-lactam

Strain and plasmid	Relevant genotypes (supplement in *trans*)	β-lactamase activity^a
		Uninduced	Induced ^b
PAO1	ampG ⁺ ampP ⁺	22.2 ± 9.7	221.4^c ± 9.2
PAOampG	ampG ^- ampP ⁺	20.4 ± 6.2	28.8^d ± 3.3
PAOampP	ampG ⁺ ampP ^-	4.2 ± 6.2	32.2^d ± 3.3
PAOampG/pKKF69	ampG^-ampP⁺ (ampG⁺)	8.4 ± 1.4	87.6 ± 14.4
PAOampP/pKKF73	ampG⁺ampP^- (ampP⁺)	8.8 ± 1.8	217.9 ± 35.5
PAOampG/pKKF73	ampG^-ampP⁺ (ampP⁺)	2.1 ± 2.0	14.4 ± 1.9
PAOampP/pKKF69	ampG⁺ampP^- (ampG⁺)	5.3 ± 1.9	10.6 ± 2.7

^a Cultures at OD600 of 0.6-0.8 were divided in two. One set was induced with 500 μg/ml benzyl-penicillin for three hours before harvesting. Assays were performed on sonicated lysate using nitrocefin as a chromogenic substrate. One milliunit of β-lactamase is defined as 1 nanomole of nitrocefin hydrolyzed per minute per microgram of protein. Assays were performed in triplicate.
^b Induction was carried out using 500 μg/ml benzyl-penicillin
^c p < 0.05 compared to uninduced PAO1
^d p < 0.05 compared to induced PAO1

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