Molecular Pathogens 2024, Vol.15, No.4, 170-178 http://microbescipublisher.com/index.php/mp 172 Figure 1 TEM images of various stages of predation (Adopted from Cavallo et al., 2021) Image caption: Images I, II and III showB. bacteriovorus HD100 (indicated with arrows) attached to the outer surface of a prey cell or in its immediate surroundings. Image IV shows a late stage of predation where the new-born predators are in the bdelloplast, prior to its disruption (Adopted from Cavallo et al., 2021) 3.3 Other emerging predatory bacterial species In addition to Bdellovibrio bacteriovorus and Myxococcus xanthus, other predatory bacteria are emerging as potential biocontrol agents. For instance, Bacteriovorax stolpii HI3 and Myxococcus sp. MH1 have been isolated from freshwater environments and characterized for their predation capabilities. B. stolpii HI3 exhibits rapid and extensive predation on a wide spectrum of Gram-negative bacteria, although prey bacteria can regrow through phenotypic resistance. In contrast, Myxococcus sp. MH1 shows lower predation efficiency but longer-lasting effects (Osińska et al., 2020; Inoue et al., 2022). These findings highlight the diverse predation strategies and environmental preferences of different predatory bacteria, suggesting their potential for biotechnological applications in various settings. 4 Predatory Bacteria as a Tool Against Pathogens 4.1 Mechanisms of action against pathogens Predatory bacteria, such as Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus, exhibit unique mechanisms to combat pathogens. These bacteria prey on Gram-negative bacteria by attaching to their prey, penetrating their outer membrane, and consuming their cellular contents. This process involves a free-living, invasive attack phase followed by an intracellular reproductive phase, where the predator degrades the host's macromolecules and reuses them for its own growth (Figure 2) (Madhusoodanan, 2019; Makowski et al., 2019). Mathematical models have been instrumental in understanding these mechanisms, allowing researchers to predict the dynamics of predator-prey interactions and the potential effectiveness of predatory bacteria in various environmental conditions (Summers and Kreft, 2022). The study by Makowski et al. (2019) revealed the unique mechanism by which carnivorous Bdellovibrio grow and reproduce through the degradation and utilization of host resources, providing new insights for the development of novel antimicrobial therapies, particularly in addressing multidrug-resistant pathogens. These predatory bacteria hold promise as "living antibiotics" for combating various pathogenic infections.
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