Project description:Microbial consortia consist of a multitude of prokaryotic and eukaryotic microorganisms. Their interaction is critical for the functioning of ecosystems. Until now, there is limited knowledge about the communication signals determining the interaction between bacteria and fungi and how they influence microbial consortia. Here, we discovered that bacterial low molecular weight arginine-derived polyketides trigger the production of distinct natural products in fungi. These compounds are produced by actinomycetes found on all continents except Antarctica and are characterized by an arginine-derived positively charged group linked to a linear or cyclic polyene moiety. Producer bacteria can be readily isolated from soil as well as fungi that decode the signal and respond with the biosynthesis of natural products. Both arginine-derived polyketides and the compounds produced by fungi in response shape microbial interactions.
Project description:Elevated atmospheric CO2 can influence the structure and function of rhizosphere microorganisms by altering root growth and the quality and quantity of compounds released into the rhizosphere via root exudation. In these studies we investigated the transcriptional responses of Bradyrhizobium japonicum cells growing in the rhizosphere of soybean plants exposed to elevated atmospheric CO2. The results of microarray analyses indicated that atmospheric elevated CO2 concentration indirectly influences on expression of large number of Bradyrhizobium genes through soybean roots. In addition, genes involved in C1 metabolism, denitrification and FixK2-associated genes, including those involved in nitrogen fixation, microanaerobic respiration, respiratory nitrite reductase, and heme biosynthesis, were significantly up-regulated under conditions of elevated CO2 in the rhizosphere, relative to plants and bacteria grown under ambient CO2 growth conditions. The expression profile of genes involved in lipochitinoligosaccharide Nod factor biosynthesis and negative transcriptional regulators of nodulation genes, nolA and nodD2, were also influenced by plant growth under conditions of elevated CO2. Taken together, results of these studies indicate that growth of soybeans under conditions of elevated atmospheric CO2 influences gene expressions in B. japonicum in the soybean rhizosphere, resulting in changes to carbon/nitrogen metabolism, respiration, and nodulation efficiency.
