AI-2-mediated signalling in bacteria

Abstract

Success in nature depends upon an ability to perceive and adapt to the surrounding environment. Bacteria are not an exception; they recognize and constantly adjust to changing situations by sensing environmental and self‐produced signals, altering gene expression accordingly. Autoinducer‐2 (AI‐2) is a signal molecule produced by LuxS, an enzyme found in many bacterial species and thus proposed to enable interspecies communication. Two classes of AI‐2 receptors and many layers and interactions involved in downstream signalling have been identified so far. Although AI‐2 has been implicated in the regulation of numerous niche‐specific behaviours across the bacterial kingdom, interpretation of these results is complicated by the dual role of LuxS in signalling and the activated methyl cycle, a crucial central metabolic pathway. In this article, we present a comprehensive review of the discovery and early characterization of AI‐2, current developments in signal detection, transduction and regulation, and the major studies investigating the phenotypes regulated by this molecule. The development of novel tools should help to resolve many of the remaining questions in the field; we highlight how these advances might be exploited in AI‐2 quorum quenching, treatment of diseases, and the manipulation of beneficial behaviours caused by polyspecies communities.

Inhibition ofSteptococcus mutansbiofilm formation by extracts ofTenacibaculumsp. 20J, a bacterium with wide-spectrum quorum quenching activity

“…According to the hypothesis proposed by Kolenbrander et al [19], high levels of AI-2 would accelerate the growth of pathogens while reducing growth of commensal bacteria, contributing to subgingival plaque formation and maturation and leading to periodontal diseases. However, LuxS is also a central metabolic enzyme which plays a crucial role in methionine metabolism [20] and participates in protein, RNA, and DNA synthesis [17], and therefore, the effects observed when its gene is mutated have to be interpreted carefully. Furanones, which are known to inhibit communication based on acyl homoserine lactone (AHL) and AI-2 signals [21], have been reported to affect biofilm formation in S. mutans .…”

Programming the group behaviors of bacterial communities with synthetic cellular communication

“…One such example is the communication systems mediated by the universal signaling molecule autoinducer-2 (AI-2), a furanosyl borate diester synthesized by LuxS from S-adenosylmethionine and present in roughly half of all sequenced bacterial genome [81,82]. Towards programmable behaviors in multiple bacterial species, AI-2 is hence an ideal candidate for exploitation.…”

Post-Segregational Killing, Altruistic Cell Death, and Other Toxin/Antitoxin Fallacies

“…One of the main problems with the claim of quorum sensing 90 via EDF is the necessity of adding rifampicin to see an effect (Kolodkin-Gal, et al, 2007); however, quorum-sensing systems do not, in general, require antibiotic pre-treatments to function, and the addition of rifampicin to inhibit transcription should activate many of the type I TA systems in E. coli in which the antitoxins are labile. Furthermore, no genes have been shown to be controlled by EDF nor has a protein import or export system been elucidated; yet, quorum-sensing systems are based on secreted signals being 95 either recognized by surface proteins or being imported and then affecting gene expression, like AI-2 (Pereira, et al, 2013) and indole (Lee, et al, 2015) in E. coli. Also, the protein from which EDF is supposed to be derived, Zwf, contains the sequence NNWDN, not NNWNN (Kumar, et al, 2016).…”