Quorum quenching activity inAnabaenasp. PCC 7120: identification of AiiC, a novel AHL-acylase

Abstract

Many bacteria use quorum sensing (QS) to coordinate responses to environmental changes. In Gram-negative bacteria, the most extensively studied QS systems rely on the use of N-acylhomoserine lactones (AHLs) signal molecules. Some bacteria produce enzymes that are able to inactivate AHL signals produced by other bacteria and hence interfere with QS-mediated processes via a phenomenon known as quorum quenching. Acylase-type AHL degradation activity has been found in the biomass of the filamentous nitrogen-fixing cyanobacterium Anabaena (Nostoc) sp. PCC 7120, being absent from the culture media. The gene all3924 has been identified and cloned whose product exhibits homology to the acylase QuiP of Pseudomonas aeruginosa PAO1, demonstrating that it is at least partially responsible for the AHL-acylase activity. The recombinant enzyme, which was named auto-inducer inhibitor from Cyanobacteria (AiiC), shows broad acyl-chain length specificity. Because the presence of AHLs in the biomass of nitrogen-fixing cultures of Anabaena sp. PCC 7120 has been described recently, AiiC could represent a self-modulatory system to control the response to its own QS signals but could also be involved in the interference of signalling within complex microbial communities in which Cyanobacteria are present.

Mini-review: Inhibition of biofouling by marine microorganisms

“…This enzyme, named 'autoinducer inhibitor from cyanobacteria' (AiiC), showed broad acyl chain length specificity and was produced during the exponential growth phase, but disappeared after 24 h. The AiiC enzyme could be used by the cyanobacterium to control the response of its own QS signals, but can potentially be used to interfere with signalling within mixed microbial communities. The search for the acylase sequences revealed the presence of similar genes in other cyanobacteria, such as Nostoc punctiforme, N. violaceus and Synechocystis sp., which indicate that these enzymes may be widespread among cyanobacteria (Romero et al 2008).…”

“…PCC 7120 (Romero et al 2008). This enzyme, named 'autoinducer inhibitor from cyanobacteria' (AiiC), showed broad acyl chain length specificity and was produced during the exponential growth phase, but disappeared after 24 h. The AiiC enzyme could be used by the cyanobacterium to control the response of its own QS signals, but can potentially be used to interfere with signalling within mixed microbial communities.…”

Inhibition ofSteptococcus mutansbiofilm formation by extracts ofTenacibaculumsp. 20J, a bacterium with wide-spectrum quorum quenching activity

“…The pellet was washed with 15 ml of phosphate buffered saline (PBS) pH 6.5, resuspended in 1.5 ml of the same buffer, sonicated for 5 min in ice, and centrifuged at 16,000 × g for 30 min at 4°C. The PCEs obtained in this way were filtered through 0.22 μm and stored at 4°C [34]. Total protein concentration in the PCEs was estimated by Lowry’s method [35].…”

Exploiting Quorum Sensing To Confuse Bacterial Pathogens

“…strain PCC 7120 and a Shewanella sp. isolated from the fish gut, respectively (49,50). Applied studies with Aac have been limited to transformation of aac into the fish pathogen Vibrio anguillarum, where it was demonstrated to decrease AHL accumulation and interrupt biofilm formation in vitro (50); no studies of AiiC inhibition of pathogenesis have been published.…”