N-Acyl Homoserine Lactone-Mediated Quorum Sensing with Special Reference to Use of Quorum Quenching Bacteria in Membrane Biofouling Control

Abstract

Membrane biofouling remains a severe problem to be addressed in wastewater treatment systems affecting reactor performance and economy. The finding that many wastewater bacteria rely on N-acyl homoserine lactone-mediated quorum sensing to synchronize their activities essential for biofilm formations; the quenching bacterial quorum sensing suggests a promising approach for control of membrane biofouling. A variety of quorum quenching compounds of both synthetic and natural origin have been identified and found effective in inhibition of membrane biofouling with much less environmental impact than traditional antimicrobials. Work over the past few years has demonstrated that enzymatic quorum quenching mechanisms are widely conserved in several prokaryotic organisms and can be utilized as a potent tool for inhibition of membrane biofouling. Such naturally occurring bacterial quorum quenching mechanisms also play important roles in microbe-microbe interactions and have been used to develop sustainable nonantibiotic antifouling strategies. Advances in membrane fabrication and bacteria entrapment techniques have allowed the implication of such quorum quenching bacteria for better design of membrane bioreactor with improved antibiofouling efficacies. In view of this, the present paper is designed to review and discuss the recent developments in control of membrane biofouling with special emphasis on quorum quenching bacteria that are applied in membrane bioreactors.

Languages and dialects: bacterial communication beyond homoserine lactones

“…Similar to Photorhabdus and pseudomonads, bacterial communication is often linked to virulence. Inhibition of LuxR-type receptors by specific agonists or antagonists, or inactivation of the respective signaling molecule, has already been observed for acyl-HSL-dependent QS systems and is termed quorum quenching [11]. Overall, muzzling the bacteria is a promising target for novel species-specific antimicrobials and a promising alternative to classical antibiotics.…”

Process-Oriented Review of Bacterial Quorum Quenching for Membrane Biofouling Mitigation in Membrane Bioreactors (MBRs)

“…However, the use of such a recombinant strain is hardly conceivable because of its very poor chances of survival in a real MBR but also because of the need to introduce antibiotics to maintain its QQ activity. Considering the significant number of natural QQ bacteria that have been identified to date (reviewed by Czajkowski and Jafra [39] and Lade et al [3]), the isolation of an indigenous QQ bacterium from a real MBR appeared to be the most reasonable method. Thus, Rhodococcus sp.…”

“…A major part of the biocake is composed of biofilm, which refers to the bacterial tendency to grow as a confined population forming cell clusters embedded in a self-produced slimy matrix composed of extracellular polymeric substances (EPS) [1,2]. In the last decade, several studies have focused on demonstrating the involvement of Quorum Sensing (QS) in biofouling, as reviewed by Lade et al [3,4] and Siddiqui et al [5]. QS is defined as cell-to-cell communication enabling the bacteria to harmonize their behavior and to function as a coordinated social cluster.…”

“…Thus, the prevalent bacterial communication in MBRs is believed to be Gram-negative QS which is ensured through AHLs as autoinducers. These molecules are composed of a lactone ring and an acylated chain containing four to 18carbons as reviewed by Lade et al [3] (Figure 1). …”

“…Recently, three interesting reviews have given overviews of the QS and QQ mechanisms, together with summaries of all the QSIs and all the QS-based ways to mitigate membrane biofouling in general [3,4,5]). However, these reviews do not plainly explain biofouling in MBRs: the links between QQ and the physical phenomena of the MBR process are not explored in depth, and the recent trends in QS-based biofouling mitigation are not fully supported by numerical data.…”