ROLE OF PROTEIN PQQ IN PHOSPHATE SOLUBILIZING ABILITY AND LEVELS OF PQQE GENE EXPRESSION IN THE NATIVE PEANUT BACTERIUM SERRATIA SP S119.

LILIANA M. LUDUEÑA, ADRIANA FABRA, TANIA TAURIAN,

La Falda

Workshop; pgpr latinoamérica 2014; 2014

Universidad Nacional de Quilmes, Río Cuarto y de Antioquia

Introduction: Of the total P present in the soil only 0, 1% is available to the plants. This problem can be overcome to some extent by P-solubilizing microbes. In Gram negative bacteria this mineral phosphate solubilization phenotype is attributed to the secretion of organic acids such as gluconic acid. The enzyme glucose dehydrogenase catalyzes the oxidation of glucose to gluconic acid and requires PQQ protein for its activity. PQQ is encoded by an operon consisting of at least 5 genes. Among these genes, pqqE gene is highly conserved even though it function remains undetermined. Objetives: Analyze the role of PQQ protein on the mineral phosphate solubilizing activity of Serratia sp. S119 and the expression of pqqE gene under P-limiting conditions. Material and methods: Serratia sp S119 and Serratia sp RSLpqqE- strains were grown in LB medium. Complementation experiments using synthetic PQQ protein were performed with mutant RSLpqqE-. Soluble P released by the bacteria was determined in NBRIP-BPB medium at 10, 24 and 48 h. The CFU/ml and the pH value of supernatants of each sample were also measured. RT PCR qualitative analysis and quantitative real-time PCR were performed to evaluate expression of pqqE gene under P-limiting condition. RESULTS: The addition of PQQ to the bacterial growth medium restored phosphate solubilizing ability of pqqE- mutant reaching similar values of wt strain at the three time points of bacterial growth tested. Complemented mutant also showed a diminished supernatant pH value as the wild type strain. RT-PCR analysis showed that pqqE gene from Serratia sp was expressed in both phosphate starvation and available soluble P conditions. Expression levels of pqqE gene at 10 h of growth under phosphate starvation condition were similar to that from bacteria growing with available soluble P. CONCLUSIONS: PQQ protein is involved in the phosphate solubilizing ability of Serratia sp S119 and according to our results in this bacterium pqqE gene expression seems to be constitutive. Área temática: mecanismos probióticos.