Microbially produced fertilizer provides rhizobacteria to hydroponic tomato roots by forming beneficial biofilms

Hydroponic cultivation of Solanum lycopersicum (tomato) is important, and high tomato production depends on the use of nitrogen and phosphate fertilizers. We had developed a microbial fertilizer (MF), which is mainly composed of nitrate. To investigate the effect of MF on plant growth, hydroponic tomato was grown with MF or commercial inorganic fertilizer (IF), and the microbiomes of the rhizosphere and the liquid phase were analyzed by confocal microscopy and high-throughput sequencing. Plant biomass and biofilm formation were increased by growth in MF compared to IF. The microbial commu-nity structures of tomato roots and hydroponic water differed between the two conditions, and three operational taxonomic units (OTUs) dominated in plants grown with MF. The three OTUs were related to Rudaea spp., Chitinophaga spp., and Stenotrophobacter terrae, which are reported to be disease-suppressive epiphytic or endophytic microbes of plant roots. Because these three OTUs also predominated in the MF itself, they were likely provided to the rhizosphere or endophytic environments of tomato roots via hydroponic water.

Automated summary

This study shows that the use of microbial fertilizer (MF) can increase biomass and biofilm formation in hydroponic tomato plants. The microbial community structures of tomato roots and hydroponic water are affected by MF compared to commercial inorganic fertilizer (IF), especially with the dominance of three specific operational taxonomic units (OTUs) related to disease-suppressive microbes.