Abstract
In the search of new and safe antibacterial compounds, the quorum sensing system (QS) modulation by natural products has been studied. As a result, many plant-derived compounds have been identified as potent quorum sensing inhibitors. Piper nigrum L. (black pepper) ethanolic extract inhibits the QS in some Gram-negative bacteria but the active components have not been previously identified. Thus, the objective of this work was to identify the P. nigrum peppercorns main components that block the QS, applying bioassay and chromatographic techniques. Piperine and trichostachine were identified as the main components responsible for the quorum quenching (QQ) activity of P. nigrum peppercorns extract. Piperine at 30 mg/L, decreased the violacein production by Chromobacterium violaceum CV026 by 35%, without affecting bacterial growth. Piperine concentration of 40 mg/L decreases violacein production by C. violaceum CV026 by 70% and growth in only 4.34%. Trichostachine at 50 mg/L decreases violacein production by C. violaceum CV026 by 12%, without affecting bacterial growth. P. nigrum extract concentration of 0.5 g/L decreased violacein production in 40 % and no effects on growth were observed. Neither P. nigrum extract, piperine, nor trichostachine did affect QS of Pseudomonas aeruginosa PAO1. Data here described exhibit the potential of piperamides as modulators of QS, not previously reported.
Highlights
Microbial communication comprises the coordinate response mechanisms to changes in the environment, that some microorganisms have developed
Subsequent to the 2, 3, 5-triphenyltetrazolium chloride (TTC) application, these two bands acquired a pink hue (Figure 1C). This colouration change is due to TTC reduction by the active cells of C. violaceum CV026, as interpreted by Seidler and van Noorden (1994)
These results indicate that the components retained at retention factor (Rf) of 0.07 and 0.21 are the main compounds responsible for the quorum quenching (QQ) in the P. nigrum extract, since these compounds inhibited the violacein production but not the bacterial growth
Summary
Microbial communication comprises the coordinate response mechanisms to changes in the environment, that some microorganisms have developed. The quorum sensing system (QS) is the most studied microbial communication mechanism (Fuqua and Greenberg, 2002; Abisado et al, 2018). Via QS, microorganisms evaluate their cell density and, above a threshold level, trigger collective development changes through synthesis, detection and response to chemical signals known as autoinducers (Nealson, 1977; Fuqua and Greenberg, 2002). One of the autoinducer-compounds family synthesized by Gram-negative bacteria is the denominated acyl homoserine lactones (AHLs) (Schuster et al, 2013). The Gram-negative soil bacterium Chromobacterium violaceum, in response to QS, modulates its violacein production, a purple antibiotic. The main autoinducer produced by C. violaceum ATCC 31532 is the
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