Role of prodigiosin and chitinases in antagonistic activity of the bacterium Serratia marcescens against the fungus Didymella applanata.

The molecular features of antagonism of the bacterium Serratia marcescens against the plant pathogenic fungus Didymella applanata have been studied. The chitinases and the red pigment prodigiosin (PG) of S. marcescens were isolated and characterized.

Extracellular chitinases of mutant superproducing strain Serratia marcescens M-1.

Four extracellular proteins with chitinase activity capable of binding chitin substrates have been revealed in the culture liquid of chitinase superproducing mutant strain M-1 of Serratia marcescens. Proteins were analyzed by SDS-PAGE and MALDI-TOF mass spectrometry. Based on the data obtained, the proteins were identified as typical chitinases of S.

[Extracellular chitinase production by wild-type B-10 and mutant M-1 strains of Serratia marcescens].

Molecular weights of extracellular chitinases from wild-type B-10 (62, 54, 43, 38, and 21 kDa) and mutant M-1 strains of Serratia marcescens (62, 52, 43, 38, and 21 kDa) were estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the absence of chitin inductors, chitinolytic enzymes were not found in the culture liquid of B-10, while M-10 cells produced the chitinase complex (to 470 pU/cell). Crystalline chitin insignificantly stimulated the synthesis of chitinases with molecular weights of 62, 54, and 21 kDa by B-10 (up to 20 pU/cell), but caused overproduction of all chitinases by the mutant strain (up to 2600 pU/cell).

[Isolation and properties of extracellular lipase of native (B-10) and mutant (M-1) Serratia marcescens strains].

The cultivation conditions of wild-type strain V-10 and mutant strain M-1 (overproducer of endonuclease and chitinase) of Serratia marcescens optimal for extracellular lipase biosynthesis were determined. The strain V-10 displayed the maximal lipase yield (840 AU/ml) after 10-12 h of cultivation; the strain M-1 (33 AU/ml), after 25-30 h. The data showed that extracellular lipases from V-10 and M-1 can be precipitated in a weakly acid medium (pH 5.

[Obtaining of mutants of Streptomyces fradiae producing tylosin by action of nitrosomethylurea on synchronously germinating spores].

The method of localized mutagenesis was applied to obtain mutants of Streptomyces fradiae producing higher amounts of tylosin. The populations of the germinating spores were subjected to a short-term treatment with nitrosomethylurea during different periods of the first DNA replication cycle. The method reveals defines periods sensitive to mutation induction and isolates a mutant producing a 60% increase in the yield of tylosin as compared to that provided by the stock strain.