The Predatory Properties of Bradymonabacteria, the Representative of Facultative Prey-Dependent Predators

Bradymonabacteria, as the representative of the facultative prey-dependent predators, were re-classified from the preceding <i>Deltaproteobacteria</i> into the phylum <i>Myxococcota</i> and proposed as a novel class named <i>Bradymonadia</i>. However, it was ambiguous whether their predatory pattern and properties were similar to those of the other myxobacterial predators. Therefore, the physiologic features were compared to determine the similarities and differences during the process of group attack and kin discrimination. Comparative genomic analyses were performed to conclude the core genome encoded commonly by bradymonabacteria, <i>Myxococcia</i>, and <i>Polyangia</i>. In conclusion, we proposed that bradymonabacteria have a predation pattern similar to the that of the representative of opportunistic predators like <i>Myxococcus xanthus</i> but with some subtle differences. Their predation was predicted to be initiated by the needle-less T3SS*, and the S-motility mediated by T4P also participated in the process. Meanwhile, their group attacks relied on cell contact and cell destiny. Inter-species (strains) kin discriminations occurred without the existence of T6SS. However, no extracellular lethal substance was detected in the fermentation liquor culture of bradymonabacteria, and the death of prey cells could only be observed when touched by their cells. Moreover, the prey-selective predation was observed when the predator encountered certain prey from <i>Bacillus</i> (G⁺), <i>Algoriphagus</i> (G^-), and <i>Nocardioides</i> (G⁺). Bradymonabacteria can be regarded as a potential consumer and decomposer, and preying on many sea-dwelling or human pathogenic bacteria allows this group a broad application prospect in marine culture and clinical disease control. Our study will provide more evidence for its exploitations and applications.