Characterization of a novel thermostable N-acylhomoserine lactonase from the thermophilic bacterium Thermaerobacter marianensis

Abstract

Thermaerobacter marianensis is an extremely thermophilic bacterium, which was isolated from the Mariana Trench, with an optimal growth temperature of approximately 75 °C. N-Acylhomoserine lactone (AHL) is a quorum-sensing signal molecule used by many gram-negative bacteria. Here, we report the identification of an AHL-degrading gene homolog (designated aiiT) in the genome of T. marianensis JCM 10246. AiiT has 59.7%, 21.2%, and 11.2% identity to AhlS from Solibacillus silvestris, AiiA from Bacillus cereus, and AidC from Chryseobacterium sp., respectively. Homologs of aiiT were also found in Thermaerobacter nagasakiensis, T. composti, and T. subterraneus. A purified AiiT-maltose binding fusion showed high AHL-degrading activity against N-hexanoyl-L-homoserine lactone, N-octanoyl-L-homoserine lactone, and N-decanoyl-L-homoserine lactone at temperatures ranging from 40 to 80 °C. HPLC analysis revealed that AiiT functions as an AHL-lactonase that catalyzes AHL ring opening by hydrolyzing lactones. AiiT displayed maximal activity at high temperatures (60-80 °C) and showed higher thermostability than other AHL lactonases.

Keywords: Acylhomoserine lactone; Lactonase; Quorum sensing; Thermaerobacter; Thermostable enzyme.