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Applied Biochemistry and Microbiology (v.48, #3)
Antibacterial metabolites of lactic acid bacteria: Their diversity and properties by L. G. Stoyanova; E. A. Ustyugova; A. I. Netrusov (pp. 229-243).
The review is devoted to literature data on antimicrobial metabolites produced by lactic acid bacteria (LAB), which have long been used for the preparation of cultured dairy products. This paper summarizes data on low-molecular-weight antimicrobial substances, which are primary products or by-products of lactic fermentation. Individual sections are devoted to a variety of antifungal agents and bacteriocins produced by LAB; their potential use as food preservatives has been discussed. The characteristics and classification of bacteriocins are presented in a greater detail; their synthesis and mechanism of action are described using the example of nisin A, which belongs to class I lantibiotics synthesized by the bacterium Lactococcus lactis subsp. lactis. The mechanism of action of class II bacteriocins has been demonstrated with lacticin. Prospective directions for using LAB antimicrobial metabolites in industry and medicine are discussed in the Conclusion.
The involvement of Pseudomonas bacteria in induced systemic resistance in plants (Review) by U. Jankiewicz; M. Kołtonowicz (pp. 244-249).
This article reviews the most recent results of studies on the mechanism of induced systemic resistance (ISR) elicited in plants by non-pathogenic bacteria of the genus Pseudomonas. Several examples of Pseudomonas strains eliciting resistance against fungal phytopathogens in different species of crop plants are presented. Literature data dealing with bacterial elicitors and the effect of their interaction with plant receptors are quoted. Special focus is focused on the controversial issue of the correlation between the synthesis of pathogenesis-related proteins (PRs) and ISR.
Antioxidant activity of hydroxy derivatives of coumarin by M. V. Potapovich; D. I. Metelitza; O. I. Shadyro (pp. 250-256).
The inhibition efficiency (antioxidant activity) of hydroxy derivatives of coumarin, such as esculetin, dicumarol, and fraxetin, was studied in the methemalbumin-H2O2-tetramethylbenzidine (TMB) pseudoperoxidase system at 20°C in a buffered physiological solution (pH 7.4) containing 6% DMF and 0.25% DMSO. The inhibitor’s efficiency was quantitatively characterized by the inhibition constants (K i, μM) and the inhibition degree (%). The K i values for esculetin, dicumarol, and fraxetin were 9.5, 15, and 26 μM, respectively. Esculetin and fraxetin inhibited pseudoperoxidase oxidation of TMB in a noncompetitive manner; dicumarol, in a mixed manner. The inhibiting activity of esculetin in peroxidase-catalyzed TMB oxidation at pH 6.4 is characterized by a K i value equal to 1.15 μM, and the inhibition process is competitive. Esculetin was found to be the most effective antioxidant of plant origin among all derivatives previously studied in model biochemical systems.
E. coli propionyl-CoA synthetase is regulated in vitro by an intramolecular disulfide bond by Y. Guo; D. J. Oliver (pp. 257-261).
The E. coli propionyl-CoA synthetase (PCS) was cloned, expressed, purified, and analyzed. Kinetic analyses suggested that the enzyme preferred propionate as substrate but would also use acetate. The purified, stored protein had relatively low activity but was activated up to about 10-fold by incubation with dithiothreitol (DTT). The enzyme activation by DTT was reversed by diamide. This suggests that the protein contains a regulatory disulfide bond and that the reduction to two sulfhydryl groups activates PCS while the oxidation to a disulfide leads to its inactivation. This idea was tested by sequential mutagenesis of the 9 Cys in the protein to Ala. It was revealed that the C128A and C315A mutants had wildtype enzyme activity but were no longer activated by DTT or inhibited by diamide. The data obtained indicate that two Cys residues could be involved in redox-regulated system through formation of an intramolecular disulfide bridge in PCS.
Role of polymer complexes in the formation of biofilms by corrosive bacteria on steel surfaces by L. M. Purish; L. G. Asaulenko; D. R. Abdulina; V. N. Vasil’ev; G. A. Iutinskaya (pp. 262-269).
The composition of exopolymer complexes (EPCs), synthesized by the monocultures Desulfovibrio sp. 10, Bacillus subtilis 36, and Pseudomonas aeruginosa 27 and by microbial associations involved in the corrosion of metal surfaces has been studied. An analysis of the monosaccharide composition of carbohydrate components, as well as the fatty acid composition of the lipid part of EPCs, was carried out by gasliquid chromatography (GLC). It was found that bacteria in biofilms synthesized polymers; this process was dominated by glucose, while the growth of bacteria in a suspension was marked by a high rhamnose content. Hexouronic acids and hexosamine have been revealed as a part of B. subtilis 36 and P. aeruginosa 27 EPCs. Qualitative differences were revealed in the fatty acid composition of exopolymers in biofilms and in a bacterial suspension. It was shown that the transition to a biofilm form of growth led to an increase in the unsaturation degree of fatty acids in the exopolymers of associative cultures. The results can be used to develop methods to control microbial corrosion of metal surfaces.
Role of superoxide anion radicals in the bacterial corrosion of metals by D. V. Belov; A. A. Kalinina; T. N. Sokolova; V. F. Smirnov; M. V. Chelnokova; V. R. Kartashov (pp. 270-274).
It was found that seven strains of bacteria can cause corrosion damage to aluminum, its alloys, and zinc. With respect to the studied metals, the most active bacteria were Proteus vulgaris 1212 and Pseudomonas aeruginosa 969. Superoxide anion radicals were demonstrated to play a role in the initiation of corrosive damage to aluminum and zinc, while bacterial exometabolites participate in the later stages of this process.
Effect of volatile metabolites from germinating seeds on the reproduction of the bacteria Listeria monocytogenes and Yersinia pseudotuberculosis by M. L. Sidorenko; L. S. Buzoleva (pp. 275-279).
The biological activity of volatile metabolites of germinating seeds of cabbage (Brassica oleacia), carrot (Daukus carota), salad (Zactuca sativa), and corn (Zea mays L.) against Listeria monocytogenes and Yersinia pseudotuberculosis was studied. It was shown that volatile metabolites are transfer factors and can be the sole carbon and energy source for these bacteria. Methanol is the main substance affecting their growth and reproduction.
Auxin synthesis by the higher fungus Lentinus edodes (Berk.) sing in the presence of low concentrations of indole compounds by O. M. Tsivileva; E. A. Loshchinina; O. E. Makarov; V. E. Nikitina (pp. 280-289).
The auxin formation in a submerged culture of the xylotrophic basidiomycete Lentinus edodes (Berk.) Sing (Lentinula edodes (Berk.) Pegler) (shiitake) is studied. Biologically active substances of an indole nature are identified, “the effect of small doses” of which lies in not only the stimulation of growth of the mycelium (indole-3-acetic acid, 2 × 10−7–2 × 10−4 g/l), but also in the induction of tryptophan-independent paths of auxin biosynthesis. The above-mentioned path is realized in the presence of exogenous indole (1 × 10−3–1 × 10−4 g/l), as well as while inducing the biosynthesis of indole-3-acetic acid by its microadditives (1 × 10−5−1 × 10−8 g/l), and is accompanied by the formation of anthranilic acid (up to 1.5 mg/l). Induction of the generative development stage of shiitake by indole derivatives is revealed. It was found that among the studied compounds only indoleacetamide at a concentration of an order of ×10−4 g/l in the culture fluid of L. edodes had a pronounced stimulatory effect on the formation of shiitake’s brown mycelial film.
Induction, purification and molecular characterization of sulfhydryl oxidase from an Egyptian isolates of Aspergillus niger by H. Moubasher; A. A. Fahmi; M. Abdur-Rahman (pp. 290-294).
The conditions for the sulfhydryl oxidase (SOX) production and activity from an Egyptian isolate of Aspergillus niger were optimized. Purification and determination of the kinetic properties (K m and V max) of the purified enzyme have been done. The possibility for the SOX induction using L-Cys (as a natural substrate) was studied to determine whether SOX could be produced as an inducible enzyme in addition to being a constitutive one (i.e. whether induction leads to increase SOX production and activity or not). The optimum temperature and pH for its activity were found to be 60°C and 5.5, respectively. The activity of the induced intracellular SOX, was measured according to Ellman’s method using the standard GSH oxidation where it reached 94% while that of non-induced one reached only 27.6%. This wide difference in activity between the induced and non-induced SOX indicates the successful L—Cys-induction of the SOX production (i.e. SOX from A. niger AUMC 4947 is an inducible enzyme). Molecular characterization of the pure SOX revealed that it is constituted of two 50–55 KDa subunits. K m and V max were found to be 6.0 mM and 100 μM/min/mg respectively.
α-L-rhamnosidase from Aspergillus clavato-nanicus MTCC-9611 active at alkaline pH by Vinita Yadav; Saroj Yadav; Sarita Yadav; K. D. S. Yadav (pp. 295-301).
An a-L-rhamnosidase secreting fungal strain has been isolated and identified as Aspergillus clavato-nanicus MTCC-9611. The enzyme was purified to homogeneity from the culture filtrate of the fungus using concentration by ultrafiltration membrane and ion-exchange chromatography on CM-cellulose. The native PAGE analysis confirmed the homogeneity of the purified enzyme. The SDS-PAGE analysis of the purified enzyme revealed a single protein band corresponding to the molecular weight 82 kDa. The α-L-rhamnosidase activity of Aspergillus clavato-nanicus MTCC-9611 had optimum at pH 10.0 and 50°C. The K m values of the enzyme were 0.65 mM and 0.95 mM using p-nitrophenyl α-L-rhamnopyranoside and naringin as a substrates respectively. The enzyme transforms naringin to prunin at pH 10.0 and further hydrolysis of prunin to naringenin does not occur under these reaction conditions that makes α-L-rhamnosidase activity of Aspergillus clavato-nanicus MTCC-9611 promising enzyme to get prunin for pharmaceutical purposes.
Biosynthesis of fumiquinazolines by the fungus Penicillium thymicola by V. P. Zhelifonova; T. V. Antipova; A. G. Kozlovskii (pp. 302-306).
Biosynthesis of fumiquinazolines F and G (FQs), PC-2, and pigments by the fungus P. thymicola VKM FW-869 is directly dependent on the content of carbon substrate (mannitol) in the medium. Pigment production prevailed at all of the tested mannitol concentrations. The necessary conditions for predominant FQ biosynthesis by the fungus P. thymicola are carbon source (mannitol) limitation and presence of NaCl in the cultivation medium. NaCl has a regulatory effect on the formation of secondary metabolites by enhancing FQ biosynthesis and reducing pigment formation. The maximum values of FQ biosynthesis and inhibition of pigment production are obtained at a mannitol concentration of 20 g/l and 2.5% NaCl in the medium.
Chitin-glucan complex in cell walls of the Peltigera aphthosa lichen by N. R. Meichik; D. V. Vorob’ev (pp. 307-311).
Cell walls and chitin-glucan complexes isolated from uneven-aged components of the thallus of the Peltigera aphthosa lichen were studied. The mass fraction of the cell wall and chitin-glucan complexes increased with age, but the content of nitrogen in these structures decreased with age. The basal area of the thallus was characterized by the largest mass fraction of the chitin-glucan complex from the dry mass of the thallus; the apical area, by the largest mass fraction of chitin in the complex. It was demonstrated that in P. aphthosa, the degree of deacetylation of chitin in the complex (depending on the age) was 33 and 54% in the apical and basal areas, respectively. The suggested method of functional analysis of chitin-glucan complexes for the presence of free amino groups in them can be used for studying other lichenified fungi.
Effect of particle size on the enzymatic hydrolysis of polysaccharides from ultrafine lignocellulose particles by V. V. Shutova; A. I. Yusipovich; E. Yu. Parshina; D. O. Zakharkin; V. V. Revin (pp. 312-317).
The efficiency of the enzymatic hydrolysis of wood polysaccharides ground into ultrafine particles (UFPs) has been investigated. The content of reducing sugars (RS’s) in powdered raw materials and the yield of sugars during enzymatic hydrolysis have been shown to depend on the particle size. Laser interference microscopy and dynamic light scattering studies have shown that increasing the grinding time from 20 to 40 min resulted in the formation of particles ranging from 2 to 200 nm in size. Enzymatic hydrolyzates of UFPs mostly contained glucose and galactose. The grinding intensity (mill rotation rate) and time had a significant effect on the extent of the enzymatic hydrolysis of wood.