The Role of Quorum Sensing Molecules in Bacterial–Plant Interactions

Abstract

Quorum sensing (QS) is a system of communication of bacterial cells by means of chemical signals called autoinducers, which modulate the behavior of entire populations of Gram-negative and Gram-positive bacteria. Three classes of signaling molecules have been recognized, Al-1, Al-2, Al-3, whose functions are slightly different. However, the phenomenon of quorum sensing is not only concerned with the interactions between bacteria, but the whole spectrum of interspecies interactions. A growing number of research results confirm the important role of QS molecules in the growth stimulation and defense responses in plants. Although many of the details concerning the signaling metabolites of the rhizosphere microflora and plant host are still unknown, Al-1 compounds should be considered as important components of bacterial–plant interactions, leading to the stimulation of plant growth and the biological control of phytopathogens. The use of class 1 autoinducers in plants to induce beneficial activity may be a practical solution to improve plant productivity under field conditions. In addition, researchers are also interested in tools that offer the possibility of regulating the activity of autoinducers by means of degrading enzymes or specific inhibitors (QSI). Current knowledge of QS and QSI provides an excellent foundation for the application of research to biopreparations in agriculture, containing a consortia of AHL-producing bacteria and QS inhibitors and limiting the growth of phytopathogenic organisms.

N -acyl homoserine lactones lactonase est816 suppresses biofilm formation and periodontitis in rats mediated by Aggregatibacter actinomycetemcomitans

“…Biofilm formation and maturation are mainly regulated by quorum sensing (QS), which depends on the synthesis of small signal molecules that regulate virulence factor expression and biofilm development in a density-dependent manner [ 5 ]. Acyl-homoserine lactones (AHLs) are important QS-related signaling molecules that are mainly produced by Gram-negative bacteria [ 6 ]. AHLs have been isolated from several oral pathogens in dentine caries and dental plaque [ 7 ].…”

Impact of CeO2 nanoparticles on the microbiota of the S. flos-cuculi L. (Caryophyllaceae) rhizosphere

“…The actions of mycorrhizae and PGPR can mitigate these effects by intervening in the ROS compounds produced in the root system, thereby reducing the mimetic and catalytic peroxidase-like activity of CeNPs. [90][91][92][93][94][95][96] Considering climate change, these conditions characterized by reduced water and humidity content in soils are expected to become increasingly prevalent. In such scenarios, in addition to the abovementioned effects, different studies reported a direct beneficial effect of nCeO 2 .…”

Biofilm-Forming Ability of Phytopathogenic Bacteria: A Review of its Involvement in Plant Stress

“…The disease cycle, which comprises differentiated stages and is represented in Figure 1, starts with a source of inoculum and ends with the appearance of symptoms such as tumors [106], decay and chlorosis [107], blight [108], wilting [109], rot [110], and cankers [111]. QS is responsible for regulating pathogenicity and colonization [83,112], and some phytopathogenic bacteria may have more than one QS system (featuring AHLs or diffusible signal factors, DSF) as well as a virulence factor modulation system [113]. For bacteria such as E. amylovora, P. syringae, Xanthomonas spp., and Ralstonia spp., T3SS are also involved in pathogenesis since they enable the direct introduction of pathogenic proteins into host cells.…”

“…The synthesis of these polymers and that of cellulose, another component of the biofilm matrix, are positively regulated by an increase in intracellular c-di-GMP [82,115]. QS is responsible for regulating pathogenicity and colonization [83,112], and some phytopathogenic bacteria may have more than one QS system (featuring AHLs or diffusible signal factors, DSF) as well as a virulence factor modulation system [113]. For bacteria such as E. amylovora, P. syringae, Xanthomonas spp., and Ralstonia spp., T3SS are also involved in pathogenesis since they enable the direct introduction of pathogenic proteins into host cells.…”