Premise of the study: The antimicrobial properties and toxicity of Euphorbia plant latex make it a hostile environment to microbes. However, when specimens from Euphorbia spp. were propagated in tissue culture, microbial growth was observed routinely, raising the question whether the latex of this diverse plant genus can be a niche for viable microbiota.
Methods: Latex from a diseased Euphorbia mandravioky plant and a healthy vegetative cutting was sampled aseptically and selective media were used to isolate axenic microbial cultures. The microorganisms were identified by 16S/SSU rRNA Sanger gene sequencing. Latex from a phylogenetically diverse set of Euphorbia species was collected and genomic microbial DNA extracted. Deep sequencing of bar-coded amplicons from phylogenetically informative gene fragments was used to measure bacterial and fungal species richness and evenness and composition.
Key results: Bacterial and fungal isolates from the diseased and healthy E. mandravioky, respectively, were identified by marker gene sequencing. Euphorbia latex, a presumably inhospitable niche for microbial growth, was found to contain unexpectedly complex bacterial (mean: 44.0 species per sample; 12 plants analyzed) and fungal (mean: 20.9 17 species per sample; 22 plants analyzed) communities using culture-independent methods.
Conclusions: Our results suggest that Euphorbia plant latex, a hostile antimicrobial environment, unexpectedly supports diverse bacterial and fungal communities. The ecological role of these microorganisms, and potential interactions with their host plant, is unexplained and warrants further research.