Predatory Bacteria: A Potential Ally against Multidrug-Resistant Gram-Negative Pathogens

Multidrug-resistant (MDR) Gram-negative bacteria have emerged as a serious threat to human and animal health. Bdellovibrio spp. and Micavibrio spp. are Gram-negative bacteria that prey on other Gram-negative bacteria. In this study, the ability of Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus to prey on MDR Gram-negative clinical strains was examined. Although the potential use of predatory bacteria to attack MDR pathogens has been suggested, the data supporting these claims is lacking. By conducting predation experiments we have established that predatory bacteria have the capacity to attack clinical strains of a variety of ß-lactamase-producing, MDR Gram-negative bacteria. Our observations indicate that predatory bacteria maintained their ability to prey on MDR bacteria regardless of their antimicrobial resistance, hence, might be used as therapeutic agents where other antimicrobial drugs fail. © 2013 Kadouri et al

An Eye to a Kill: Using Predatory Bacteria to Control Gram-Negative Pathogens Associated with Ocular Infections

Ocular infections are a leading cause of vision loss. It has been previously suggested that predatory prokaryotes might be used as live antibiotics to control infections. In this study, Pseudomonas aeruginosa and Serratia marcescens ocular isolates were exposed to the predatory bacteria Micavibrio aeruginosavorus and Bdellovibrio bacteriovorus. All tested S. marcescens isolates were susceptible to predation by B. bacteriovorus strains 109J and HD100. Seven of the 10 P. aeruginosa isolates were susceptible to predation by B. bacteriovorus 109J with 80% being attacked by M. aeruginosavorus. All of the 19 tested isolates were found to be sensitive to at least one predator. To further investigate the effect of the predators on eukaryotic cells, human corneal-limbal epithelial (HCLE) cells were exposed to high concentrations of the predators. Cytotoxicity assays demonstrated that predatory bacteria do not damage ocular surface cells in vitro whereas the P. aeruginosa used as a positive control was highly toxic. Furthermore, no increase in the production of the proinflammatory cytokines IL-8 and TNF-alpha was measured in HCLE cells after exposure to the predators. Finally, injection of high concentration of predatory bacteria into the hemocoel of Galleria mellonella, an established model system used to study microbial pathogenesis, did not result in any measurable negative effect to the host. Our results suggest that predatory bacteria could be considered in the near future as a safe topical bio-control agent to treat ocular infections. © 2013 Shanks et al

Shedding Light on Microbial Predator-Prey Population Dynamics Using a Quantitative Bioluminescence Assay

This study assessed the dynamics of predation by Bdellovibrio bacteriovorus HD 100. Predation tests with two different bioluminescent strains of Escherichia coli, one expressing a heat-labile bacterial luciferase and the other a heat-stable form, showed near identical losses from both, indicating that protein expression and stability are not responsible for the "shutting-off" of the prey bioluminescence (BL). Furthermore, it was found that the loss in the prey BL was not proportional with the predator-to-prey ratio (PPR), with significantly greater losses seen as this value was increased. This suggests that other factors also play a role in lowering the prey BL. The loss in BL, however, was very consistent within nine independent experiments to the point that we were able to reliably estimate the predator numbers within only 1 h when present at a PPR of 6 or higher, Using a fluorescent prey, we found that premature lysis of the prey occurs at a significant level and was more prominent as the PPR ratio increased. Based upon the supernatant fluorescent signal, even a relatively low PPR of 10-20 led to approximately 5 % of the prey population being prematurely lysed within 1 h, while a PPR of 90 led to nearly 15 % lysis. Consequently, we developed a modified Lotka-Volterra predator-prey model that accounted for this lysis and is able to reliably estimate the prey and bdelloplast populations for a wide range of PPRs.close0

Emerging horizons for industrial applications of predatory bacteria

26 p.-4 fig.-2 tab. The Ecology of Predation at the Microscale pp 173-194This chapter reviews the potential of the predatory bacteria Bdellovibrio bacteriovorus, an obligate predator of other gram-negative bacteria, as a biotechnological tool. Due to the unique lifestyle and the different applications, predatory bacteria have awakened interest to be developed as a lytic tool. The lack of physiological and metabolic information makes difficult this development. However, in the last years, different approaches have been described in order to understand the physiology, morphology, and metabolism of the predators, as well as the population dynamics of the prey-predator interactions. Besides its potential of “living antibiotic”, predatory bacteria have been proposed as a biocontrol agent in the food industry or aquaculture. A recent work using B. bacteriovorus as a biological lytic tool for the recovery of intracellular bioproducts highlighted the potential use of predators in industrial bioprocesses. The bottlenecks of using other Bdellovibrio and like organisms (BALOs) have been also considered and discussed during this chapter.This work was supported by the European Union’s Horizon 2020 Research and Innovation Programme, grant agreement no. 760994-2 (ENGICOIN), the Spanish Ministry of Science, Innovation and Universities (BIO2017-83448-R) and the Community of Madrid (P2018/ NMT4389).Peer reviewe