In Pseudomonas aeruginosa, the expression of a number of
virulence factors, as well as biofilm formation, are controlled by quorum sensing (QS). N-Acylhomoserine
lactones (AHLs) are an important class of signaling molecules involved in bacterial QS and in many pathogenic bacteria
infection and host colonization are AHL-dependent. The AHL signaling molecules are subject to inactivation mainly by
hydrolases (
Enzyme Commission class number EC 3) (i.e. N-acyl-
homoserine lactonases and N-
acyl-homoserine-lactone acylases). Only little is known on quorum quenching mechanisms of
oxidoreductases (EC 1). Here we report on the identification and structural characterization of the first
NADP-dependent
short-chain dehydrogenase/reductase (SDR) involved in inactivation of N-(3-oxo-dodecanoyl)-L-homoserine
lactone (3-oxo-C(12)-HSL) and derived from a metagenome library. The corresponding gene was isolated from a soil metagenome and designated bpiB09. Heterologous expression and crystallographic studies established BpiB09 as an
NADP-dependent
reductase. Although AHLs are probably not the native substrate of this metagenome-derived
enzyme, its expression in P. aeruginosa PAO1 resulted in significantly reduced
pyocyanin production, decreased motility, poor biofilm formation and absent
paralysis of Caenorhabditis elegans. Furthermore, a genome-wide transcriptome study suggested that the level of lasI and rhlI transcription together with 36 well known QS regulated genes was significantly (≥10-fold) affected in P. aeruginosa strains expressing the bpiB09 gene in pBBR1MCS-5. Thus AHL
oxidoreductases could be considered as potent tools for the development of quorum quenching strategies.