Impact of quorum sensing from native peanut phosphate solubilizing Serratia sp. S119 strain on interactions with agronomically important crops

Bacteria communicate with each other using a language based on the use of autoinducer molecules (AI) to collectively control gene expression through the process known as quorum sensing (QS). The N- acylhomoserine lactones (AHLs) are the most common AIs known in Gram-negative bacteria. Numerous genes encoding QS systems have been reported in plant beneficial endophytic bacterial genomes although there are fewer studies evaluating the participation of QS in the mechanisms of plant growth promotion. The aim of this study was to describe the genetic background and the types of AHLs produced by a phosphate-solubilizing bacterial strain isolated from the roots of peanut Serratia sp. S119, and to evaluate the participation of these AIs in promoting the growth of plants of agronomic importance. Bioinformatics analysis indicated that the genome of S119 strain harbors genes encoding proteins involved in the production and detection of AHLs. This strain was found to produce the QS molecules C8-HSL, C10-HSL, 3-OH-C8-HSL and 3-OH-C10-HSL with the latter being the most abundant AHL. By overexpressing a heterologous lactonase enzyme in Serratia sp. S119, this strain was depleted in the production of all AHLs with the exception of 3-OH-C10-HSL which levels were reduced by 50%. The ability to solubilize phosphate, produce biofilms and promote plant growth was analyzed in the AHL attenuated strain. This strain was able to maintain the ability to solubilize phosphate while biofilm production was significantly reduced. Plant inoculation assays with the QS attenuated strain showed differences responses on growth parameters of the three plants employed. These results indicate that the AHLs from the phosphate solubilizing Serratia sp. S119 strain may not affect its ability to solubilize phosphate. However, they play a role in biofilm formation that is a key trait for bacterial colonization in its interaction with plant species.