The influence of ortho- and para-diphenoloxidase substrates on pigment formation in black yeast-like fungi.

Dothideaceous black yeast-like fungi (BYF) are known to synthesise DHN-melanin that is inhibited by the systemic fungicide tricyclazole. The final step of the DHN melanin pathway is the conjoining of 1,8-DHN molecules to form the melanin polymer. There are several candidate enzymes for this step, including phenoloxidases such as tyrosinase and laccases, peroxidases, and perhaps also catalases. We analysed the type polyphenoloxidases that are involved in biosynthesis of BYF melanins. For that purpose we used substrates of o-diphenoloxidases (EC 1.10.3.1.): 4-hydroxyphenyl-pyruvic acid, L-beta-phenyllactic acid, tyrosine, pyrocatechol, 3,4-dihydroxyphenylalanine and homogentisic acid, as well as substrates of p-diphenoloxidases (EC 1.10.3.2.): syringaldazine, resorcinol, p-phenylenediamine, phloroglucinol, guaiacol and pyrogallic acid. Fourteen strains of black yeasts originating from different natural biotopes were investigated. The tested strains could be divided into four groups based on their ability to produce dark pigments when cultivated on aromatic substrates of o- and on p-diphenoloxidases. It was established that syringaldazine, pyrogallic acid and 4-hydrophenyl-pyruvic acid, beta-phenyllactic acid optimally promote melanin biosynthesis. Average intensity of pigmentation of all strains studied was minimal when guaiacol was used as a substrate. The present investigation indicates that the melanisation process may involve more enzymes and more substrates than those commonly recognised. Black yeasts are likely to contain a multipotent polyphenoloxidase.

[The effect of yeast glycans in experimental LPS-induced endotoxicosis]. / Vliianie glikanov drozhzhei pri éksperimental'nom éndotoksikozom, vyzvannom LPS.

The immunomodulating action of yeast glycans obtained from Rhodotorula rubra (rhonasan) and Sporobolomyces albo-rubescens (heteroglycan Sp-50) was studied under the conditions of experimental endotoxicosis in mice, induced by the injection of the sublethal dose of Escherichia coli lipopolysaccharide (LPS). In endotoxicosis glycans produced a protective effect, depending on the time of injection. The study demonstrated that after the injection of glycans the survival rate of the animals increased and the LPS-inhibited function of peritoneal macrophages and B lymphocytes was completely or partially restored.

[The bacteriocin typing of Klebsiella pneumoniae strains]. / Bakteriotsinotipirovanie shtammov Klebsiella pneumoniae.

Results of bacteriocin typing of 196 strains of the Klebsiella genus are presented. They are typified by their sensitivity to bacteriocins and by their production using colicinogenic and indicating strains from collection of P. Fredericq [correction of Frederick], D. G. Kudlai, N. I. Koshanova as well as klebocinogenic K-type cultures of Klebsiella previously suggested by the authors. Investigation results have shown sufficient stability of a bacteriocinotype of the cultures confirmed by the population analysis. It is concluded that bacteriocin typing may be recommended as an additional method in epidemiological labelling of Klebsiella cultures.