Background: Continuous adaptation of the bacterial membrane is required in response to changing environmental conditions. Results: Pseudomonas aeruginosa ORF PA0919 codes for an alanyl-phosphatidylglycerol hydrolase that is anchored to the periplasmic surface of the inner membrane. Conclusion: The elucidated enzymatic activity implies a new regulatory circuit for the fine tuning of cellular alanyl-phosphatidylglycerol concentrations.