Echinacea purpurea microbiota: bacterial-fungal interactions and the interplay with host and non-host plant species in vitro dual culture.

Important evidence is reported on the antimicrobial and antagonistic properties of bacterial endophytes in Echinacea purpurea and their role in the modulation of plant synthesis of bioactive compounds. Here, endophytic fungi were isolated from E. purpurea, and the dual culture approach was applied to deepen insights into the complex plant-microbiome interaction network. In vitro experiments were carried out to evaluate the species specificity of the interaction between host (E. purpurea) and non-host (E. angustifolia and Nicotiana tabacum) plant tissues and bacterial or fungal endophytes isolated from living E. purpurea plants to test interactions between fungal and bacterial endophytes. A higher tropism towards plant tissue and growth was observed for both fungal and bacterial isolates compared to controls without plant tissue. The growth of all fungi was significantly inhibited by several bacterial strains that, in turn, were scarcely affected by the presence of fungi. Finally, E. purpurea endophytic bacteria were able to inhibit mycelial growth of the phytopathogen Botrytis cinerea. Bacteria and fungi living in symbiosis with wild Echinacea plants interact with each other and could represent a potential source of bioactive compounds and a biocontrol tool.

Isolation and characterisation of a new antagonistic Burkholderia strain from the rhizosphere of healthy tomato plants.

A new Burkholderia strain (PVFi5A) which exhibits antagonism towards many bacterial and fungal plant pathogens has been partially characterised. This strain was isolated from the rhizosphere of tomato plants and was referred to the Burkholderia cepacia complex on the basis of cultural, morphological and biochemical characteristics, including determination of the 16S ribosomal DNA sequence and fatty acid profile. Strain PVFi5A is a Gram-negative, aerobic bacterium, oxidase- and catalase-positive, motile with a polar tuft of flagella, able to grow on a variety of media without producing diffusible pigments; it is avirulent to onion, able to grow at 41 degrees C and resistant to several antibiotic substances. Its fatty acid profile contains the hydroxy acids 18:1 20H, 14:0 3OH and 16:0 3OH, but not the hydroxy acids 16:0 2OH. The antagonistic activity of strain PVFi5A is due to its production of various, as yet unidentified, antimicrobial compounds, one or more of which may differ from those reported previously for certain 'B. cepacia' strains. The ability of PVFi5A to suppress the growth of important bacterial and fungal phytopathogens makes this strain a potential biocontrol agent.