Different phosphate sources are associated with specific, active bacterial communities in the rhizosphere and endorhiza of barley

Phosphate is a macronutrient and often the limiting growing factor of many ecosystems. The aim of this work was to assess the effect of various phosphate sources on the active bacterial microbiota of barley rhizosphere and endorhiza, grown under salt stress. Barley was grown on nutrient–depleted soil amended with either Ca(H2PO4)2 (CaP), Gafsa rock phosphate (GAFSA), sodium hexaphytate (NaHex) or not amended. RNA was extracted from both rhizosphere and endorhiza of barley roots; the obtained 16S cDNA was sequenced by IonTorrent and analyzed with QIIME. Relationships between bacteria and phosphate sources were assessed by correlation network analysis.CaP–amended barley showed the highest yield, followed by GAFSA–, NaHex– and no phpsphate– amended plants. Phosphate source significantly affected the structure of the active microbiome in both habitats, and CaP determined higher diversity indices. Co–occurrence network analysis showed that Nocardioaceae and Acidobacteriaceae OTUs were enriched by CaP, while Oxalobacteriaceae OTUs (related to the genus Massilia) were enriched by both NaHex and GAFSA. Negative correlations were also identified, indicating complementary taxa under different phosphate amendments. This study shows for the first time the differential response of the rhizosphere– and endorhiza bacterial microbiota of barley to various phosphate sources in soil, thus shedding light onto this largely unknown aspect of the soil microbiome ecology and interactions.