Bacterial fitness for plant colonization is influenced by plant growth substrate

Abstract

O_LIBacteria colonize plants and contribute to their health. Despite advances in our understanding of bacterial plant colonization, the extent to which growth substrate influences the molecular mechanisms enabling bacteria to efficiently colonize plants remains poorly understood. C_LIO_LITo evaluate if genes important for plant colonization are influenced by substrate, we used randomly barcoded transposon mutagenesis sequencing (RB-TnSeq) in Paraburkholderia graminis OAS925, an efficient rhizosphere colonizer, and Brachypodium distachyon plants grown in six different substrates. C_LIO_LIOf the 382 rhizosphere colonization genes that we identified in strain OAS925, 348 genes (91.1%) are dependent on the growth substrate evaluated, and 34 genes (8.9%) are shared across all the substrates. To further characterize the plant colonization fitness genes, we compared our data to growth in 110 distinct in vitro conditions. To validate our results, we used individual mutants of selected genes and tested them in different growth substrates. We also show the influence of substrate on colonization by P. phytofirmans PsJN, Variovorax sp. OAS795 and Rhizobium sp. OAE497. C_LIO_LIOur data confirms that bacterial fitness for plant colonization is strongly influenced by plant growth substrate type, and highlights the importance of taking this parameter into consideration when engineering bacterial strains for improved host colonization. C_LI