Exploring the Function of Quorum Sensing Regulated Biofilms in Biological Wastewater Treatment: A Review

Abstract

Quorum sensing (QS), a type of bacterial cell–cell communication, produces autoinducers which help in biofilm formation in response to cell population density. In this review, biofilm formation, the role of QS in biofilm formation and development with reference to biological wastewater treatment are discussed. Autoinducers, for example, acyl-homoserine lactones (AHLs), auto-inducing oligo-peptides (AIPs) and autoinducer 2, present in both Gram-negative and Gram-positive bacteria, with their mechanism, are also explained. Over the years, wastewater treatment (WWT) by QS-regulated biofilms and their optimization for WWT have gained much attention. This article gives a comprehensive review of QS regulation methods, QS enrichment methods and QS inhibition methods in biological waste treatment systems. Typical QS enrichment methods comprise adding QS molecules, adding QS accelerants and cultivating QS bacteria, while typical QS inhibition methods consist of additions of quorum quenching (QQ) bacteria, QS-degrading enzymes, QS-degrading oxidants, and QS inhibitors. Potential applications of QS regulated biofilms for WWT have also been summarized. At last, the knowledge gaps present in current researches are analyzed, and future study requirements are proposed.

Natural Strategies as Potential Weapons against Bacterial Biofilms

“…A red algae-halogenated furanone, Dilsea pulchra , has been reported to have effective anti-biofilm properties [ 263 ]. Some synthetic and natural brominated furanones have been reported as significant QS inhibitors against gram-negative and positive bacterial species [ 264 , 265 , 266 , 267 ].…”

Application of psychrotolerant quorum quenching Planococcus versutus sp. L10.15T to membrane bioreactors for biofouling control at low temperatures

“…Cells secrete and sense signaling molecules (e.g., N-acyl homoserine lactones or AHLs) to detect their population density. [4][5][6][7] When the concentration of signaling molecules exceeds a threshold value, QS controls specific group behaviors, including biofilm formation. 8 Previous studies reported some challenges posed by low temperatures in MBRs.…”

“…, N -acyl homoserine lactones or AHLs) to detect their population density. 4–7 When the concentration of signaling molecules exceeds a threshold value, QS controls specific group behaviors, including biofilm formation. 8…”

The Antibacterial Effect of Cannabigerol toward Streptococcus mutans Is Influenced by the Autoinducers 21-CSP and AI-2

“…The first one encompasses the homologous QS networks in Gram-negative bacteria where the autoinducers are acylated homoserine lactones (AHL) operating in genetic pathways akin to the LuxIR in Vibrio fischeri [ 6 , 7 ]. The second category is the two-component signal-transduction pathway of Gram-positive bacteria, with post-translational processed peptides serving as the messengers [ 8 ]. The third category is the interspecies communication that relies on autoinducer-2 (AI-2) synthases and the LuxS protein family [ 9 ].…”