Where are signal molecules likely to be located in anaerobic granular sludge?

A sustainable method for effective regulation of anaerobic granular sludge: Artificially increasing the concentration of signal molecules by cultivating a secreting strain

“…According to the method used for the previous studies concerning the different distribution of three types of signal molecules in AnGS (Feng et al, 2014), 100 mL of the sludge-water mixture was used to simultaneously extract and measure AHLs and DSF. The pretreated mixture was extracted with an equivalent volume of ethyl acetate, evaporated to dryness, and the dried material redissolved in 2 mL of 50% acetonitrile for subsequent analysis (Wang et al, 2012).…”

“…The bioluminescence was measured by a multifunctional microplate reader (SpectraMax M5, USA), as described in the previous studies (Feng et al, 2014).…”

“…DSF-QS regulation controlled the average diameters at a relatively lower level, ranging from 50 to 70 lm. Previous papers had indicated the inhibition of cell aggregates and biofilm formation (Deng et al, 2011;Feng et al, 2014), and it was expected that DSF would order cells to disperse into a broader habitat. The smaller sludge diameter mostly resulted from the intervention of DSF-QS regulation which provided a higher DSF content environment.…”

“…QS secrets signal molecules to regulate the behaviors and relationships between microorganisms to guide the expression of a particular gene when these signal molecules reach a threshold concentration (Shrout and Nerenberg, 2012). To date, the types of signal molecules found in water and wastewater treatment systems include N-acyl-homoserine lactones (AHLs) in Gram negative bacteria, autoinducer-2 (AI-2) in interspecies communication, and diffusible signal factor (DSF) in intra-and interspecies bacteria (Feng et al, 2014;Shrout and Nerenberg, 2012). There are many papers demonstrating the positive effects of AHLs or AI-2 in aerobic sludge granulation (Li and Zhu, 2014;Ren et al, 2013Ren et al, , 2010Tan et al, 2014;Liu, 2012, 2010;Zhang et al, 2011) and increasing the efficiency of the granulating process by improving granular properties.…”

“…Zhang et al (2011) speculated that the addition of boron would promote the formation of the precursor of AI-2, which resulted in accelerated aerobic granulation. After verifying the promotion of QS on aerobic granulation, Li (2014) and Wang (2014) made attempts to change the concentration of signal molecules, and both found that the granulation of aerobic granules was accelerated under an alternative feeding scheme or a comfortable pH environment with a higher concentration of AHLs.…”