Molecular Pathogens 2024, Vol.15, No.2, 50-60 http://microbescipublisher.com/index.php/mp 52 contact-dependent mechanism is central to effective prey colony invasion and consumption. Similarly, B. bacteriovorus invades the periplasm of Gram-negative bacteria, where it replicates and eventually lyses the prey (Dörr, 2023). 3.2 Secretion of lytic enzymes Once attached, microbial predators secrete a variety of lytic enzymes to break down the cell walls of their prey. M. xanthus secretes hydrolytic enzymes, including a family 19 glycoside hydrolase, which display bacteriolytic activity (Arend et al., 2020). These enzymes are particularly effective against Gram-positive bacteria, while cell-associated mechanisms are more crucial for killing Gram-negative bacteria. Streptomyces species also produce numerous lytic enzymes, such as glucanases, mannosidases, and chitinases, to digest the cell walls of yeast (Yamada et al., 2023). Additionally, B. bacteriovorus secretes specialized lytic transglycosylases to clear prey cell septum obstructions, enhancing its ability to consume prey. 3.3 Consumption and digestion After the prey cell wall is breached, microbial predators proceed to consume and digest the prey's cellular contents. M. xanthus induces prey lysis from the outside and feeds on the released biomass, a process facilitated by its gliding motility and induced cell reversals (Thiery and Kaimer, 2020). This allows M. xanthus to remain within the prey area and efficiently consume the available nutrients. B. bacteriovorus digests the prey within the periplasmic space, utilizing the prey's cellular components as nutrients (Negus et al., 2017). The production of antifungal polyenes and cholesterol oxidase by Streptomyces further destabilizes the prey cell membrane, aiding in the assimilation of yeast cells. In summary, microbial predators utilize a combination of attachment and invasion, secretion of lytic enzymes, and consumption and digestion to effectively kill and consume their prey. These mechanisms highlight the potential of microbial predators in disease management by targeting pathogenic bacteria and fungi. 4 Role in Disease Management 4.1 Targeting pathogenic bacteria Microbial predators have shown significant potential in targeting pathogenic bacteria, offering a promising alternative to traditional chemical treatments. For instance, the predatory myxobacteriumCitreicoccus inhibens has demonstrated bacteriolytic properties against both Gram-negative and Gram-positive phytopathogenic bacteria, making it a versatile biocontrol agent (Zhou et al., 2021). Additionally, the interactions between bacteria and fungi within the human microbiota can influence bacterial pathogenesis, with certain fungi regulating bacterial growth and virulence, thereby impacting human health. 4.2 Controlling fungal infections Microbial predators also play a crucial role in controlling fungal infections. The use of microbial antagonists, such as certain bacteria and fungi, has been explored for postharvest disease suppression in fruits and vegetables. These antagonists can inhibit fungal growth through various mechanisms, including competition for nutrients, mycoparasitism, and the secretion of antifungal metabolites (Dukare et al., 2019). Furthermore, the entomopathogenic fungi, which have been used as biocontrol agents for over 150 years, not only kill insect pests but also exhibit antifungal properties, contributing to plant pathogen antagonism (Bamisile et al., 2021). 4.3 Applications in agriculture and medicine The applications of microbial predators extend to both agriculture and medicine. In agriculture, microbial predators like the endosymbiotic bacteria Mycoavidus in Mortierella fungi protect their host from nematode attacks, promoting plant growth and soil health (Figure 1) (Büttner et al., 2021). Similarly, the Rhizopus-Mycetohabitans symbiosis produces rhizoxin, a toxin that defends the fungal host against protozoan and metazoan predators, highlighting the ecological role of microbial predators in maintaining soil health (Richter et al., 2022). In medicine, the potential of microbial predators is being explored for developing new antimicrobials and antivirulence factors, leveraging the interactions within the human microbiota to discover novel therapeutic
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