Transcriptomic Analysis Followed by the Isolation of Extracellular Bacteriolytic Proteases from Lysobacter capsici VKM B-2533T

The aim of the study was to search for, isolate and characterize new bacteriolytic enzymes that show promising potential for their use in medicine, agriculture and veterinary. Using a transcriptomic analysis, we annotated in Lysobacter capsici VKM B-2533^T the genes of known bacteriolytic and antifungal enzymes, as well as of antibiotics, whose expression levels increased when cultivated on media conducive to the production of antimicrobial agents. The genes of the secreted putative bacteriolytic proteases were also annotated. Two new bacteriolytic proteases, Serp and Serp3, were isolated and characterized. The maximum bacteriolytic activities of Serp and Serp3 were exhibited at low ionic strength of 10 mM Tris-HCl, and high temperatures of, respectively, 80 °C and 70 °C. The pH optimum for Serp was 8.0; for Serp3, it was slightly acidic, at 6.0. Both enzymes hydrolyzed autoclaved cells of Micrococcus luteus Ac-2230^T, Proteus vulgaris H-19, Pseudomonas aeruginosa and Staphylococcus aureus 209P. Serp also digested cells of Bacillus cereus 217. Both enzymes hydrolyzed casein and azofibrin. The newly discovered enzymes are promising for developing proteolytic antimicrobial drugs on their basis.

The Discovery of the Role of Outer Membrane Vesicles against Bacteria

Gram-negative bacteria are intrinsically resistant to many commercialized antibiotics. The outer membrane (OM) of Gram-negative bacteria prevents the entry of such antibiotics. Outer membrane vesicles (OMV) are naturally released from the OM of Gram-negative bacteria for a range of purposes, including competition with other bacteria. OMV may carry, as part of the membrane or lumen, molecules with antibacterial activity. Such OMV can be exposed to and can fuse with the cell surface of different bacterial species. In this review we consider how OMV can be used as tools to deliver antimicrobial agents. This includes the characteristics of OMV production and how this process can be used to create the desired antibacterial activity of OMV.

Deletion of alpB Gene Influences Outer Membrane Vesicles Biogenesis of Lysobacter sp. XL1

Outer membrane vesicles (OMVs) produced by Gram-negative bacteria constitute important factors in defining interactions with the extracellular milieu. Lysobacter sp. XL1 produces OMVs capable of lysing microbial cells due to the presence in their cargo of bacteriolytic protease L5 (AlpB). Although protein L5 has been functionally and biochemically characterized (including aspects of its packing into OMVs), its role in vesicle biogenesis through genetic deletion of alpB had not been studied previously. Here, we have successfully deleted alpB by allelic replacement and show that the alpB deletion mutant produces a significantly lower amount of OMVs that lack bacteriolytic activity and display altered ultrastructural characteristics in relation to the OMVs produced by the wild-type strain. These results confirm that, as previously proposed, protein L5 participates in OMV production through a mechanism that is not yet fully understood.

Lytic potential of Lysobacter capsici VKM B-2533T: bacteriolytic enzymes and outer membrane vesicles

Recent recurrent outbreaks of bacterial resistance to antibiotics have shown the critical need to identify new lytic agents to combat them. The species Lysobacter capsici VKM B-2533^T possesses a potent antimicrobial action against a number of bacteria, fungi and yeasts. Its activity can be due to the impact of bacteriolytic enzymes, antibiotics and peptides. This work isolated four homogeneous bacteriolytic enzymes and a mixture of two proteins, which also had a bacteriolytic activity. The isolates included proteins identical to L. enzymogenes α- and β-lytic proteases and lysine-specific protease. The proteases of 26 kDa and 29 kDa and a protein identified as N-acetylglycosaminidase had not been isolated in Lysobacter earlier. The isolated β-lytic protease digested live methicillin-resistant staphylococcal cells with high efficiency (minimal inhibitory concentration, 2.85 μg/mL). This property makes the enzyme deserving special attention. A recombinant β-lytic protease was produced. The antimicrobial potential of the bacterium was contributed to by outer membrane vesicles (OMVs). L. capsici cells were found to form a group of OMVs responsible for antifungal activity. The data are indicative of a significant antimicrobial potential of this bacterium that requires thorough research.

Structural and functional properties of antimicrobial protein L5 of Lysоbacter sp. XL1

The Gram-negative bacterium Lysobacter sp. XL1 secretes into the extracellular space five bacteriolytic enzymes that lyse the cell walls of competing microorganisms. Of special interest are homologous lytic proteases L1 and L5. This work found protein L5 to possess Gly-Gly endopeptidase and N-acetylmuramoyl-L-Ala amidase activities with respect to staphylococcal peptidoglycan. Protein L5 was found to be capable of aggregating into amyloid-like fibril structures. The crystal structure of protein L5 was determined at a 1.60-Å resolution. Protein L5 was shown to have a rather high structural identity with bacteriolytic protease L1 of Lysobacter sp. XL1 and α-lytic protease of Lysobacter enzymogenes at a rather low identity of their amino acid sequences. Still, the structure of protein L5 was revealed to have regions that differed from their equivalents in the homologs. The revealed structural distinctions in L5 are suggested to be of importance in exhibiting its unique properties.