Melissospora conviva gen. nov., sp. nov., a novel actinobacterial genus isolated from beehive through cross-feeding interactions

Most micro-organisms remain unculturable under standard laboratory conditions, limiting our understanding of microbial diversity and ecological interactions. One major cause of this uncultivability is the loss of access to essential cross-fed metabolites when bacteria are removed from their natural communities. During a bioprospecting campaign targeting actinomycetes of an <i>Apis mellifera</i> beehive, we identified five isolates (DT32, DT45^T, DT55, DT59 and DT194) that required co-cultivation for growth recovery, suggesting a dependence on microbial interactions in their native habitat. Whole-genome sequencing and phylogenetic analysis positioned these isolates within a distinct lineage of <i>Micromonosporaceae</i>, separate from the five officially recognized clades of the <i>Micromonospora</i> genus. A combination of microscopic, chemotaxonomic and physiological characterizations further supported their uniqueness. Notably, they exhibited high auxotrophy, being unable to use all carbon sources tested, likely due to genome reduction (4.6 Mbp) compared to other <i>Micromonosporaceae</i>. Pangenomic comparisons with their closest <i>Micromonospora</i> relatives revealed gene losses in key metabolic pathways, including the glyoxylate bypass and the Entner-Doudoroff pathway, which may explain their metabolic reliance. These findings reveal a highly specialized, ecologically adapted lineage with deep evolutionary divergence and further support microbial interdependence isolation strategies to explore the microbial dark matter. We propose <i>Melissospora conviva</i> as a novel genus and species within the <i>Actinomycetota</i> phylum, with isolate DT45^T as the representative type species and type strain, which has been deposited in public collections under the accession numbers DSM 117791 and LMG 33580.