METABOLIC RESPONSES MEDIATED BY PHOSPHATE IN HERBASPIRILLUM SEROPEDICAE: CHEMOTAXIS, PHB SYNTHESIS AND ROOT COLONIZATION

GRILLO-PUERTAS, M.; VILLEGAS, J. M.; PANKIEVICZ, V.C.; TADRA-SFEIR, M.; MOTA, T.; BRUSAMARELLO-SANTOS, L.; PEDRAZA, R.O.; SOUZA, E.M.; RAPISARDA, V. A.

Salta

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB Congress; 2019

SAIB

Polyphosphate (polyP) is a molecule that plays important roles in microbial metabolism. Environmental phosphate (Pi) modulates intracellular polyP levels in Herbaspirillum seropedicae, a plant growth promoting bacteria (PGPB) associated with important agricultural crops. In low and high polyP accumulating conditions, RNA-seq transcriptional profile revealed several responses associated to energy production process, two component regulatory systems, and amino acid transport and metabolism, among others. The aim of the present work was to evaluate, in the differential polyP conditions, the molecular and phenotypical changes related to chemotaxis, polyhydroxybutyrate (PHB) synthesis and maize colonization. Assays were carried out in cells grown in high polyP condition (M+P, media containing 50 mM Pi,) or low polyP condition (M-P, with 5 mM Pi ). In M+P cells, most chemotaxis genes (tar, tsr, and che), and a wide range of flagella biosynthesis, assembly and structure genes, were up-regulated. As expected, SmR1 cells presented higher motility in M+P than those grown in M-P. Also, results showed that taxis of cells grown in M+P was significantly higher than that observed in M-P, being this difference greater in the presence of root exudates and phytohormones. Several genes related to biofilm development and colonization were down-regulated in the high polyP condition, which is in agreement with the lower biofilm formation capacity and endophytic maize root colonization observed in cells grown in this condition. Genes encoding enzymes related to PHB metabolism were up-regulated in cells grown in M+P, correlating with the higher PHB levels compared to those in cells grown in M-P. Present findings provide new insights about signals triggered by intracellular polyP that could be critical for H. seropedicae applications as PGPB.