Abstract
Quorum sensing regulates bacterial virulence determinants, therefore making it an interesting target to attenuate pathogens. In this work, we screened edible, endemic plants in Malaysia for anti-quorum sensing properties. Extracts from Melicope lunu-ankenda (Gaertn.) T. G. Hartley, a Malay garden salad, inhibited response of Chromobacterium violaceum CV026 to N-hexanoylhomoserine lactone, thus interfering with violacein production; reduced bioluminescence expression of E. coli [pSB401], disrupted pyocyanin synthesis, swarming motility and expression of lecA::lux of Pseudomonas aeruginosa PAO1. Although the chemical nature of the anti-QS compounds from M. lunu-ankenda is currently unknown, this study proves that endemic Malaysian plants could serve as leads in the search for anti-quorum sensing compounds.
Highlights
Most Gram-negative bacteria use ‘‘quorum sensing’’ (QS) to coordinate their population behaviour including expression of virulence factors through the action of extracellular signal molecules, such as the N-acyl-L-homoserine lactones (AHLs)
M. lunu-ankenda is a kind of “ulam” that is widely consumed as garden salad by the Malay community in Malaysia and it has shown no adverse effects on human health
M. lunu-ankenda shows promising anti-QS properties and it has been confirmed that its extracts inhibited QS-dependent virulence determinants of the human pathogens namely P. aeruginosa PAO1
Summary
Most Gram-negative bacteria use ‘‘quorum sensing’’ (QS) to coordinate their population behaviour including expression of virulence factors through the action of extracellular signal molecules, such as the N-acyl-L-homoserine lactones (AHLs). Sensors 2012, 12 which in turn modulates QS-mediated gene expressions [1,2]. Gram negative and Gram positive bacteria employ different signal molecules, inasmuch that the former use AHLs while the latter use post-translationally processed peptides [3,4]. Pseudomonas aeruginosa is the opportunistic Gram negative bacterium which is a well-studied model for AHL-mediated QS. Regulation of virulent factors expressed by P. aeruginosa is controlled by the las and rhl [6,7] which are arranged in a hierarchical manner such that the las system activates the rhl system [7]. Myriad virulence factors of P. aeruginosa namely pyocyanin, proteases, haemolysins, exotoxin A and exoenzyme S are QS-dependent [8,9]
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