In nature, microorganisms exist in complex communities of multiple species that interact with each other. While some of these interactions are beneficial for the partners involved, others are parasitic or even competitive. A common interaction among microorganisms is predation. Predatory bacteria show an enormous diversity of feeding strategies. At present, four basic predatory lifestyles are known, such as wolf pack" or group predation, epibiotic attachment, direct cytoplasmic invasion, and periplasmic invasion.
Among the most well researched predators are myxobacteria capable of digesting whole microcolonies by swarming on their prey. Myxococcus xanthus is a social bacterium that preys on prokaryotic and eukaryotic microorganisms. M. xanthus is a Gram-negative soil bacterium with a complex life cycle including social gliding, fruiting body formation and predation. The latter behavior is characterized by unusual mechanisms that do not resemble any of the predation mechanisms described above. M. xanthus cells can penetrate prey colonies and kill nearby cells using special enzymes. Motility gives it the advantage of being able to actively search for prey, and regulate the mechanism of cell killing in a targeted manner, such that killing factors are released in response to prey cell contact, rather than solely in response to nutritional cues.4
Source: Tomada, Puopolo, Perazzolli, Musetti, Loi and Pertot. via PubMed Central
Potential Therapeutic Agents
Predatory bacteria are Gram-negative bacteria that prey on other Gram-negative bacteria and have been considered as potential therapeutic agents against multi-drug resistant pathogens. These organisms can predate upon a wide range of pathogenic bacterial strains in both planktonic and biofilm environments. Perhaps the best studied strategy involves invading the periplasm of other Gram-negative bacteria, where they undergo a complex developmental cycle that terminates the prey cell viability and ultimately leads to the release of the predator’s progeny.2
Animal studies have confirmed that although only a small number of evidence exists regarding the safety of using predatory bacteria, predatory bacteria have the ability to attack “real-life” Gram-negative human pathogens associated with ocular infection. Furthermore, laboratory studies had revealed that the presence of high concentrations of predatory bacteria don’t appear to be harmful to human cells.3 Bdellovibrio bacteriovorus has potential as a biocontrol agent, or living antibiotic.
The genus Lysobacter includes several species that produce a range of extracellular enzymes and other metabolites with activity against bacteria, fungi (particularly against fungal root pathogen Rhizoctonia solani), oomycetes (suppress damping-off disease caused by Pythium species in sugar beet and Aphanomyces cochlioides in spinach, Swiss chard, and beets), and nematodes. Lysobacter species use a feeding strategy similar to that of myxobacteria. For efficient predation they need to outnumber their prey, suggesting that they exclusively practice group predation.
- Quantitative Analysis of Lysobacter Predation
Ivana Seccareccia,a Christian Kost,b and Markus Nettcorresponding authora Appl Environ Microbiolv.81(20); 2015 Oct
- Investigating the Responses of Human Epithelial Cells to Predatory Bacteria
Ajay K. Monnappa,1,* Wasimul Bari,b,1,* Seong Yeol Choi,1 and Robert J. Mitchella,1 Scientific ReportsPMC5024164
- An Eye to a Kill: Using Predatory Bacteria to Control Gram-Negative Pathogens Associated with Ocular Infections
Robert M. Q. Shanks,1 Viral R. Davra,2 Eric G. Romanowski,1 Kimberly M. Brothers,1 Nicholas A. Stella,1 Dipti Godboley,2 and Daniel E. Kadouri2,* PLoS Onev.8(6); 2013
- Deciphering the hunting strategy of a bacterial wolfpack
James E. Berleman and John R. Kirby* FEMS Microbiol Rev. 2009 Sep; 33(5): 942–957.