The Gram-negative bacterium Lysobacter sp. XL1 secretes lytic enzymes (L1-L5) into the culture medium. Enzyme L5 is the most recently found extracellular lytic enzyme of this bacterium. The paper presents the results of the isolation and characterization of some properties of this enzyme. Thus, enzyme L5 of Lysobacter sp. XL1 is a lytic serine protease. Earlier, the enzyme was shown to be secreted into the culture medium by means of outer membrane vesicles, which possess a lytic effect towards living cells of Erwinia caratovora B15 [Vasilyeva et al., FEBS J 2008;15:3827-3835]. This work shows the action of enzyme L5 either as a vesicle component or the homogeneous enzyme L5 on a broad range of Gram-positive and Gram-negative microorganisms. Moreover, the vesicles containing this enzyme were shown to lyze the selected test cultures more efficiently than the soluble enzyme L5. It appears to be one of the first precedents of a bacteriolytic effect mediated by the action of outer membrane vesicles filled with extracellular lytic enzymes. The results suggest that the enzyme L5 of Lysobacter sp. XL1 and the vesicles containing this enzyme can be used as an antimicrobial drug.
The CYSTM (cysteine-rich transmembrane module) protein family comprises small molecular cysteine-rich tail-anchored membrane proteins found in many eukaryotes. The Saccharomyces cerevisiae strains carrying the CYSTM genes YDRO34W-B and YBR056W-A (MNC1) fused with GFP were used to test the expression of these genes under different stresses. The YBR056W-A (MNC1) and YDR034W-B genes are expressed under stress conditions caused by the toxic concentrations of heavy metal ions, such as manganese, cobalt, nickel, zinc, cuprum, and 2.4-dinitrophenol uncoupler. The expression level of YDR034W-B was higher than that of YBR056W-A under alkali and cadmium stresses. The Ydr034w-b-GFP and Ybr056w-a-GFP proteins differ in the cellular localization: Ydr034w-b-GFP was mainly observed in the plasma membrane and vacuolar membrane, while Ybr056w-a-GFP was observed in the cytoplasm, probably in intracellular membranes. The null-mutants in both genes demonstrated decreased cell concentration and lytic phenotype when cultivated in the presence of excess manganese. This allows for speculations about the involvement of Mnc1 and Ydr034w-b proteins in manganese stress overcoming.
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