Effect of heterologous AHLs on the phosphate solubilizing ability of Serratia sp S119 and Enterobacter sp J49

LUCERO, CT; TAURIAN, T; LORDA, GS

Congreso; XVI Symposium on Biological nitrogen fi xation with NON-LEGUMES IV Latinamerican Workshop of PGPR; 2018

The bacterial phosphate solubilizing ability in the plant rhizosphere is influenced by several factors being one of them the presence of other microorganisms that share the same environment. It is widely described that bacterial communication is subject to the release of molecules of the acyl homoserine lactone (AHLs) type. The objective of this work was to evaluate the influence of heterologous AHLs potentially present in this environment on the phosphate solubilizing capacity of Serratia sp S119 and Enterobacter sp J49. Heterologous AHLs were obtained from the phosphate solubilizer strain Pseudomonas fluorescens P3, the free-living N2 fixer and producer of phytohormones Azospirillum brasilense Az39, and the soybean microsymbiont, Bradyrhizobum japonicum E109. The effect of heterologous AHLs on the phosphate solubilizing activity was analyzed by quali- and quantitative assays. For the former, Petri dishes containing NBRIP-BPB culture medium supplemented with AHLs were used and the phosphate solubilization halo formation was analyzed. For the quantitative estimation assay the modified colorimetric technique of Fiske and Subbarow (1925) was used. Bacteria were grown in liquid cultures of NBRIP supplemented with the heterologous AHLs at 28°C under agitation. Samples were taken at different times to determine soluble P content and pH. Results obtained from both assays indicated the heterologous AHLs showed no effect on the phosphate solubilizing ability of the bacteria. The low pH values obtained from the bacterial supernatants in the quantitative test, suggests that the bacteria would be expressing the main mechanism of solubilization by releasing organic acids. The results obtained indicate that the phosphate solubilization phenotype is not dependent on quorum sensing. Keyword: PLANT GROWTH PROMOTING BACTERIA; RHIZOSPHERE.