Populations of uncultivated American cranberry in sphagnum bog communities harbor novel assemblages of Actinobacteria with antifungal properties

The American cranberry (Vaccinium macrocarpon Aiton) is a perennial plant in northern latitudes that co-occurs with sphagnum mosses in uncultivated populations, in habitats characterized by high acidity, low nitrogen, and fungal pathogens that thrive in wet environments. We investigated the association of Actinobacteria with cranberry and co-inhabiting sphagnum moss and their antifungal properties, across several natural populations. Based on 16S-rRNA gene phylogeny, the majority of these species were in the genus Streptomyces. Neither site nor plant source explained the phylogenetic relationships of these isolates. Most sequences did not group with known Streptomyces sequences, indicating a potentially high diversity of novel strains from this environment. We observed antibiosis by some Actinobacteria isolates against the phytopathogenic fungus Colletotrichum acutatum and a general antagonistic fungus, Trichoderma sp. Individual isolates varied in antifungal ability within and between fungi. Variation in bacterial antifungal properties was not explained by plant species or site, but was partially related to phylogenetic relationship. These results document novel associations between cranberry and sphagnum moss with Actinobacteria, including strains capable of inhibiting fungi. These results suggest candidates for development as biological control agents in agriculture.