Adding complexity to soil food webs: Myxobacteria have broad predation spectra with bacteria, yeasts and filamentous fungi in vitro

In the multifaceted soil habitat, predation is one of the most successful strategies for obtaining food. An example of prokaryotic predators is myxobacteria. Although the prey spectra of some myxobacteria have been the subject of numerous studies, these myxobacteria are usually rare in soils compared to other myxobacterial families. Consequently, predation assays featuring easily cultivable myxobacteria provide only limited information on the myxobacterial potential and their interactions with organisms in the soil. Therefore, the prey spectrum of representatives of more common families was tested and compared with members of the model family Myxococcaceae. In a newly developed assay, the extent of lysis was tested against various Gram-positive and Gram-negative bacteria, as well as four yeasts. It was shown that Kofleria flava and Haliangium ochraceum have an equally diverse prey spectrum as the model genera Myxococcus and Corallococcus. However, less well-studied myxobacteria often lyse the prey colonies to a larger extent. Yeasts were lysed just as efficiently as bacteria. Furthermore, it was tested whether different myxobacteria can inhibit the growth of filamentous fungi. Almost every strain was able to prevent the spread of at least one fungus. H. ochraceum showed the highest activity and inhibited all fungi, including plant pathogenic Fusarium. These multiple interactions together with the high relative abundance in situ, suggest that myxobacteria, especially understudied families, could have a more important role in the soil food web than previously thought. The individual interaction spectra of the different myxobacteria provide only a glimpse at the complex relationships between the organisms in soil, which still remain understudied.