Botanicals as Quorum Quenching Molecules and Their Effect in Plant Growth Promoting Traits in Pantoea, Paenibacillus, and Rhizobium

Quorum sensing is a cell-to-cell communication mechanism that was reported in Rhizobium mayense S11R1, Pantoea dispersa YBB19B, and Paenibacillus illionoisensis YBB20 by the presence of N-acyl homoserine lactones. This study explored possible mechanisms for expressing plant growth-promoting traits meditated through the quorum-sensing molecules. To prove the above hypothesis, a quorum quenching approach was carried out to study the regulation of plant growth-promoting traits of three isolates using botanicals like Curcuma longa (Turmeric) and Andrographis paniculata (Nilavembu) extracts (500, 1000, and 1500 ppm). At 1500 ppm, indole acetic acid production was completely inhibited in all three isolates. Extracellular Polymeric Substances (EPS) production was significantly reduced in Pantoea dispersa YBB19B (24 µg/mL) when treated with nilavembu extract. Biofilm-forming ability was weakened to a greater extent in Pantoea dispersa YBB19B and Paenibacillus illionoisensis YBB20 when treated with nilavembu extract. Hence, it is concluded that plant growth promotion traits in the selected bacteria are mediated through quorum sensing.