Abstract
Acyl homoserine lactones (AHLs) are the most common class of quorum sensing signal molecules (autoinducers) that have been reported to be essential for virulence of many relevant pathogenic bacteria such as Pseudomonas aeruginosa. New approach for controlling infections of such bacteria is through quorum quenching. In this study, the acyl homoserine lactone inhibitory activity of the crude enzyme from a Bacillus weihenstephanensis-isolate P65 was characterized. The crude enzyme was found to have relatively high thermal stability and was stable in pH range 6 to 9. The crude enzyme extract was found to have lactonase activity of 36.3 U/mg total protein. Maximum enzyme activity was achieved within a range of 28–50°C and pH 6–9. None of the metals used enhanced the activity neither did EDTA inhibit it. However, a concentration of 10 mM Fe+2 reduced the activity to 73.8%. Catalytic activity and kinetic constants were determined using hexanoyl homoserine lactone as a substrate. Studying enzyme substrate specificity using synthetic standard signals displayed broad spectrum of activity. The enzyme was found to be constitutive. Isolation and complete nucleotide sequence of the respective lactonase gene were done and submitted to the Genbank database under accession code KC823046.
Highlights
Bacteria communicate with each other using a mechanism known as quorum sensing, a mechanism that is dependent on their population density and which was first reported in the bioluminescent bacterium Vibrio fischeri [1].Quorumsensing bacteria can release, detect, and respond to small signal molecules—the autoinducers (AIs)—that accumulate in the environment as the population grows [2, 3]
The majority of natural Acyl homoserine lactones (AHLs) reported to date share conserved structural characteristics, a homoserine lactone ring unsubstituted at the β- and γ-positions, which is N-acylated at the α-position with an acyl group derived from fatty acid biosynthesis [6]
We studied the activity of crude AHL degrading enzyme from the B. weihenstephanensis which was found to be closely related to lactonases that are widespread in B. thuringiensis and Bacillus cereus strains
Summary
Bacteria communicate with each other using a mechanism known as quorum sensing, a mechanism that is dependent on their population density and which was first reported in the bioluminescent bacterium Vibrio fischeri [1].Quorumsensing bacteria can release, detect, and respond to small signal molecules—the autoinducers (AIs)—that accumulate in the environment as the population grows [2, 3]. Quorumsensing systems have been found in pathogenic bacteria of plants, animals, and humans [5]. Acyl homoserine lactones (AHLs) are the most common autoinducers used by Gramnegative bacteria. The majority of natural AHLs reported to date share conserved structural characteristics, a homoserine lactone ring unsubstituted at the β- and γ-positions, which is N-acylated at the α-position with an acyl group derived from fatty acid biosynthesis (a fatty acyl group) [6]. The quorum-sensing systems can induce antibiotic production [7]; pigmentation [8]; biofilm formation [5]; and BioMed Research International
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