How do Quorum Sensing Signals Mediate Algae–Bacteria Interactions?

Abstract

Quorum sensing (QS) describes a process by which bacteria can sense the local cell density of their own species, thus enabling them to coordinate gene expression and physiological processes on a community-wide scale. Small molecules called autoinducers or QS signals, which act as intraspecies signals, mediate quorum sensing. As our knowledge of QS has progressed, so too has our understanding of the structural diversity of QS signals, along with the diversity of bacteria conducting QS and the range of ecosystems in which QS takes place. It is now also clear that QS signals are more than just intraspecies signals. QS signals mediate interactions between species of prokaryotes, and between prokaryotes and eukaryotes. In recent years, our understanding of QS signals as mediators of algae–bacteria interactions has advanced such that we are beginning to develop a mechanistic understanding of their effects. This review will summarize the recent efforts to understand how different classes of QS signals contribute to the interactions between planktonic microalgae and bacteria in our oceans, primarily N-acyl-homoserine lactones, their degradation products tetramic acids, and 2-alkyl-4-quinolones. In particular, this review will discuss the ways in which QS signals alter microalgae growth and metabolism, namely as direct effectors of photosynthesis, regulators of the cell cycle, and as modulators of other algicidal mechanisms. Furthermore, the contribution of QS signals to nutrient acquisition is discussed, and finally how microalgae can modulate these small molecules to dampen their effects.

Quorum‐quenching enzymes: Promising bioresources and their opportunities and challenges as alternative bacteriostatic agents in food industry

“…In the past 20 years, there has been an increased study of QS systems of food microorganisms (e.g., bacteria, fungi, algae, etc. ), with bacterial QS considered the most relevant QS system for the food industry (Dow, 2021; Galloway et al., 2012; Padder et al., 2018). Most bacterial QS systems are driven by three mechanisms for sensing and responding to AIs (Figure 1).…”

A methodological review on the characterization of microalgal biofilm and its extracellular polymeric substances

“…In addition to the techniques mentioned above, AFM is frequently integrated with Raman spectroscopy tools such as confocal resonance Raman microscopy (CRRM), tip‐enhanced Raman spectroscopy (TERS) and surface‐enhanced Raman spectroscopy (SERS) to provide valuable insights into the underlying cell and EPS adhesion mechanisms at different biofilm maturation phases (Keleştemur et al, 2018; Laviale et al, 2019; Lebedev et al, 2014; Schmid et al, 2008). Such combinations of topographical data, compositional data and microscopic data were worth‐mentioning to assist studies regarding quorum sensing, a chemical communication system or so‐called ‘molecular circuit’ in algal‐bacterial biofilm (Dow, 2021; Keleştemur et al, 2018). Study of AFM on colony biofilms has served as strong evidence to showcase the biofilm‐forming potential and the adhesive strength onto different substrates.…”