Quorum sensing near the coral reef at the Eilat gulf

Quorum sensing (QS) is a chemical communication system in bacteria, based on chemical signal molecules called "autoinducers". This system enables bacteria to regulate important social phenotypes such as virulence, motility, luminescence and biofilm formation. QS was discovered 25 years ago in two marine bacteria called V. fischeri and V .harveyi. When V.harveyi activates its QS system, it becomes bioluminescent and forms a biofilm layer.

In the beginning, we took six samples of water and sand from Eilat gulf, numbered from one to six, when six is the closest to the coral reef and one is the furthest. We extracted the molecules that the bacteria in each sample produce, and ran a bioassay of V.harveyi (mm30) with the molecules. Afterwards, we used TLC and LC-MS to separate the molecules in the samples that have showed activity, and did another bioassay of V.harveyi (mm30) with those fractions. The last experiment was biofilm assay of V.harveyi (bb120) with the fractions.

In the first bioassay, samples three and five were the only that have showed activity. Both inhibit the luminescence in high concentration, but also the growth of the V.harveyi.
We succeed in separating only sample five, and the masses of the fractions were 224 and 497. In the second bioassay, both fractions activated the QS system. In that bioassay the bacteria grew well in any concertation, therefore, we can presume that we took out the toxic molecules in the separation part. In the biofilm assay there was lower OD of biofilm layer as the concentration of the fractions was higher.

Following the results of all the experiments, we can assume that the bacteria that are close to the coral reef have a QS. system, and can communicate with V.harveyi.