MMBL proteins: from lectin to bacteriocin.

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bacteriocins are diverse protein toxins used in bacterial warfare.
• Monocot mannose-binding lectins (MMBLs), also known as Galanthus nivalis agglutinin (GNA) lectins, are found in various eukaryotes and possess protective functions.
• Previous research identified eukaryotic MMBLs with antifungal, insecticidal, nematicidal, and antiviral activities, and mammalian C-type lectins with bactericidal properties.

Purpose of the Study:

• To identify and characterize novel bacteriocins within the MMBL family.
• To investigate the genus-specific killer activity of these novel prokaryotic MMBLs.
• To explore the structural and functional implications of dual MMBL domains and accessory domains in bacteriocins.

Main Methods:

• Identification of novel bacteriocins in prokaryotic genomes.
• Phylogenetic analysis of bacterial MMBL modules.
• Characterization of genus-specific killer activity against Gram-negative bacteria (Pseudomonas and Xanthomonas).

Main Results:

• Discovery of the first prokaryotic MMBL member with genus-specific bacteriocin activity.
• Identification of novel bacteriocins in Gram-negative bacteria, Pseudomonas and Xanthomonas.
• Observation of dual divergent MMBL domains and accessory protease-like domains in some bacteriocins, suggesting modular task distribution and potential roles in target recognition and killing.

Conclusions:

• The discovery of prokaryotic MMBL bacteriocins expands the known repertoire of bacterial toxins.
• The presence of multiple domains suggests complex mechanisms for target specificity and activity.
• Phylogenetic analysis indicates potential trans-kingdom acquisition of ancestral MMBL genes, primarily in soil-dwelling and rhizosphere bacteria.