Abstract:
Antibiotic resistance has led to the emergence of `superbugs` that are bacteria resistant to multiple
drugs commonly prescribed for treatment of bacterial infections. Currently we are left with very
limited options to combat these infections. Many novel antibacterial approaches are under
investigation. Quorum Sensing has been reported to be extensively involved in causing bacterial
infections. It includes synthesis of signaling molecules for intercellular communication of bacteria.
Identification of Quorum Sensing signaling molecules has led to the discovery of new targets to
inhibit infections. These signaling molecules can be targeted at their production, after production
or at their recognition site by receptor protein. This process is known as Quorum Quenching and
can serve as a powerful tool to combat multidrug resistant infections without imposing selection
pressure on bacteria thus eliminating the risk of antimicrobial resistance. In the present study,
bacteria responsible for degradation of signal molecules in the bacterial pathogens have been
isolated from sludge of membrane bioreactor. Four of the isolated strains showed maximum
growth on minimal media with Acyl Homoserine Lactones (AHLs), signaling molecules in
bacteria, as their sole Carbon and Nitrogen source. These strains were characterized for their ability
to degrade AHLs and were checked for their inhibition effect on biofilms formed by the pathogenic
Pseudomonas aeruginosa. After 16S rDNA sequencing, these four strains were verified at the
species level as Bacillus cereus strain QSP03, Bacillus subtilis strain QSP10, Pseudomonas putida
strain QQ3 and Pseudomonas aeruginosa strain QSP01. Presence of three Quorum Quenching
enzymes (AHL lactonases and AHL acylases) producing genes, AiiA, PvdQ and QuiP was
confirmed via respective primers and sequencing. The AHL degradation capability and
identification of respective enzyme producing genes indicates the current bacterial isolates to be
potential Quorum Quenching strains.
