Swimming Motility in Agrobacterium tumefaciens is Controlled by Quorum Sensing and Inhibited by Garlic Bulb Extract

摘要

Bacteria can produce and sense signal molecules, allowing the whole population to initiate a concerted action once a critical concentration (corresponding to a particular population density) of the signal has been reached; a phenomenon known as Quorum Sensing (QS). The current study was conducted to examine the possible role of QS in the regulation of swimming motility of Agrobacterium tumefaciens. In addition, we investigated the anti-QS or Quorum-Quenching (QQ) activity of garlic bulb and Salvadora persica extracts. We found that treatment of A. tumefaciens culture with different exogenous QS compounds induced swimming motility. C4 AHL, C6 AHL, C7 AHL, C8AHL, CIO AHL and C14 AHL induced bacterial swimming motility by about 3.5,4,4.5,4.5, 3.5 and 4 fold, respectively, providing strong evidence that quorum sensing in A. tumefaciens controls cell motility, or at least plays a major role in its regulation. We also found that different QS compounds affect the bacterial phenotype, including the colony pattern and morphology. In addition, garlic bulb and Salvadora persica extracts were investigated for their QQ activity. While S. persica extract did not show any significant QQ activity, garlic bulb extract showed QQ activity against C4 AHL, C8 AHL, CIO AHL and C14 AHL, repressing the A. tumefaciens swimming motility induced by these QS compounds. To the best of our knowledge, this is the first report of a possible role for QS in the regulation of swimming motility in A. tumefaciens.