Project description:Gene expression patterns of the plant colonizing bacterium,Pseudomonas putida KT2440 were evaluated as a function of growth in the Arabidopsis thaliana rhizosphere. Gene expression in rhizosphere grown P. putida cells was compared to gene expression in non-rhizosphere grown cells. Keywords: Gene expression
Project description:Root exudates contain specialised metabolites that affect the plant’s root microbiome. How host-specific microbes cope with these bioactive compounds, and how this ability shapes root microbiomes, remains largely unknown. We investigated how maize root bacteria metabolise benzoxazinoids, the main specialised metabolites of maize. Diverse and abundant bacteria metabolised the major compound in the maize rhizosphere MBOA and formed AMPO. AMPO forming bacteria are enriched in the rhizosphere of benzoxazinoid-producing maize and can use MBOA as carbon source. We identified a novel gene cluster associated with AMPO formation in microbacteria. The first gene in this cluster, bxdA encodes a lactonase that converts MBOA to AMPO in vitro. A deletion mutant of the homologous bxdA genes in the genus Sphingobium, does not form AMPO nor is it able to use MBOA as a carbon source. BxdA was identified in different genera of maize root bacteria. Here we show that plant-specialised metabolites select for metabolisation-competent root bacteria. BxdA represents a novel benzoxazinoid metabolisation gene whose carriers successfully colonize the maize rhizosphere and thereby shape the plant’s chemical environmental footprint
Project description:Understanding biological diversity and distribution patterns at multiple spatial scales is a central issue in ecology. Here, we investigated the biogeographical patterns of functional genes in soil microbes from 24 arctic heath sites using GeoChip-based metagenomics and principal coordinates of neighbour matrices (PCNM)-based analysis. Functional gene richness varied considerably among sites, while the proportions of each major functional gene category were evenly distributed. Functional gene composition varied significantly at most medium and broad spatial scales, and the PCNM analyses indicated that 14-20% of the variation in total and major functional gene categories could be attributed primarily to relatively broad-scale spatial effects that were consistent with broad-scale variation in soil pH and total nitrogen. The combination of variance partitioning and multi-scales analysis indicated that spatial distance effects contributed 12% to variation in functional gene composition,whereas environmental factors contributed only 3%. This relatively strong influence of spatial as compared to environmental variation in determining functional gene distributions contrasts sharply with typical microbial phylotype/species-based biogeographical patterns in the Arctic and elsewhere. Our results suggest that the distributions of soil functional genes cannot be predicted from phylogenetic distributions because spatial factors associated with historical contingencies are relatively important determinants of their biogeography.
Project description:Understanding the biogeographical patterns and underlying drivers of microbial functional diversity is essential for anticipating climate change impacts on ecosystem functioning worldwide. However, this matter remains scarcely addressed in freshwater ecosystems. Using the high-throughput gene array GeoChip 4.0, we show that functional gene alpha diversity and compositon differ across mountains, alpha diversity declines towards high elevations and compositional turnover increases with larger elevational distances. Both continental- and mountain-scale patterns were primarily driven by climatic variables.