Metagenomic approach for the isolation and cultivation of cellulose-degrading myxobacteria

Cellulose-degrading myxobacteria are common soil microorganisms with unique morphologies and are united forming the distinct Sorangium and Byssovorax clades in the Polyangiaceae family, order Myxococcales. Cells of these fascinating bacteria can glide, form fruiting bodies and degrade agar and cellulose. However, phenotypic studies based on the swarm, fruiting bodies and cellulose degradation pattern have shown many dissimilarities among strains suggesting more potential to identify new species in Sorangium clade. Currently, nine validly described species are recognized capable of decomposing cellulose in myxobacteria, of which eight species belong to the genus Sorangium and one species to Byssovorax. With the increasing number of species recently validated in Sorangium, likely there will also be more species of Byssovorax that can be found in the environment. BLAST search analysis of Byssovorax 16S rRNA gene sequences in NCBI public database (GenBank) revealed 97-98.8 % similarity with sequences derived from clones of uncultured bacteria. In Sorangium, six 16S rRNA gene sequences derived from clones of uncultured bacteria were identified occupying novel branches and exhibiting 96.9% – 98.6% similarities with type strains. Molecular phylogenetic analysis confirmed the affiliations of these clones within Sorangium and Byssovorax clades, indicating potentially new species within these genera. Surprisingly, one sequence derived from a clone (DEN_SIP_103) may potentially represent a novel genus only if this strain can be successfully cultured in the future.