In this case we all wondered

A milestone observation of bacterial Silmitasertib is that bacteria can communicate with one another by a system called quorum sensing (QS) [8], which regulates gene expression in response to fluctuations in the cell population density [9]. The bacteria which have QS system produce quorum signaling molecules and then release them to their surroundings. When the cell population density increased to a certain value, the signals concentration reached a threshold value, and the binding of signal molecules and regulatory proteins activates quorum sensing-regulated genes to activate relevant phenotypes. Generally, signal molecules of Gram-negative bacteria are AHLs [9]. AHLs-based QS-regulated phenotypes, such as symbiosis, competence, conjugation, antibiotic production and virulence, have been studied in medicine and toxicology [10]. Recently, the biofilm formation, activity and growth rates of bacteria for the wastewater treatment have been investigated because they provide information that is required to solve problems related to water treatment [11]. Previous studies have been verified the community activity (phenol degradation) could be improved under conditions that 2 μM AHL were added to a sludge sample from an industrial wastewater treatment plant [12]. N-octanoyl-l-homoserine lactone (C8-HSL) was reported to be closely associated with membrane biofouling of the membrane bioreactor, while the formation of membrane biofilms can be prevented by quenching AHLs [13]. Moreover, De Clippeleir et al. demonstrated that the oxidation rate of Oxygen Limited Autotrophic Nitrification Denitrification (OLAND) biomass at low concentrations could be significantly increased with the addition of exogenous AHLs [14].