Mikrobiologiia最新文献

Immobilization of photobacteria in the cryogel of polyvinyl alcohol (PVA) was carried out. Immobilization was found to result in increased intensity and stability of bioluminescence. The elements determining the stability of bioluminescence were investigated. Selection of the strain was found to be of the highest importance. Among immobilized cells, Photobacterium phosphoreum exhibited the most intense and prolonged light emission, while Vibrio harveyi showed the least one. The technological procedures for cryogenic immobilization of photobacteria were determined. The role of the environment of gel formation in the preservation of the bioluminescence activity was determined. In the gels formed in rich medium for submergedcultivation of photobacteria, almost 100% luminescence activity was preserved, while light emission was considerably prolonged. Bioluminescence intensity of the preparations was shown to depend significantly on pH of the incubation medium. The pH shift to acidic values during prolonged incubation of immobilized cells was shown to be one of the factors of bioluminescence quenching. The stress effects of cryogenic immobilizationwere found to have an insignificant effect on the temperature profile of bioluminescence. Decreased reduction rate of the luciferase flavin substrate was shown to be a possible reason for bioluminescence quenching.

Effect of selenium-containing biocomposites obtained from submerged cultures of macrobasidiomycetesGanoderma applantum, G. cattienensis, G. colossus G. lucidum, G. neojaponicum, and G. valesiacum,on plant pathogenic bacteria Clavibacter michiganensis ssp. sepedonicus (Cms), Micrococcus luteus, Pectobacteriumatrosepticum, Pectobacterium carotovorum subsp. carotovorum, Pseudomonas fluorescens, Pseudomonasviridiflava, and Xanthomonas campestris was studied. Oxopropyl-4-hydroxychromenones were used as componentsof the fungal nutrient media. The bacteriostatic and bactericidal activity of the Se-containing and Sefreesubstances of fungal origin against plant pathogenic bacteria was determined using colony-forming unitscount, the agar well diffusion method, and by turbidity measurements of bacterial suspensions. The compositesproduced from the extracellular metabolites of G. cattienensis SIE1302 with 4-hydroxy-3-(3-oxo-1,3-diphenyl propyl)-chromen-2-one (S(45)), and of G. lucidum SIE1303 with 4-hydroxy-3-(3-oxo-1-(3-nitrophenyl)-3-phenylpropyl)-chromen-2-one (S(NO2)) possessed the most pronounced antibacterial actionagainst Cms. The composites produced from the isolates of G. valesiacum 120702 with S(NO2) showed themaximal antibacterial activity against Xanthomonas campestris B-610. High antimicrobial effect of G. lucidum1315 with S(NO2) against Xanthomonas campestris B-610 and of G. colossus SIE1301 against Pseudomonas fluorescensEL-2.1 was revealed. The pioneering information on the biological activity of coumarin series compoundsin their application for producing the substances of fungal origin was obtained.

A complex of Ag/AgCl nanoparticles was synthesized on the basis of the extracellular polysaccharide of Azotobacter chroococcum XU1 and 10 mM AgNO3 solution. The complex was characterized by UV spectroscopy, X-ray diffraction, and scanning electron microscopy. Colloidal solutions of the complex had absorption peaks at 260 and 420 nm, indicating the formation Ag/AgCl nanoparticles. The size of the nanoparticles varied from 6 to 50 nm. The nanobiocomposite consisting of the exopolysaccharide matrix and Ag/AgCl nanoparticles exhibited a fungicidal effect against such plant pathogens as Fusarium oxysporum f. sp. vasinfectum and Verticillium dahliae.

Yeast abundance and species diversity of endophytic complexes in galls (cecidia) formed on the leaves of Salix fragilis, Salix caprea, Quercus robur, Tilia cordata, and Ulmus laevis and the epiphytic yeast communities of undamaged leaves of these plants were studied. Dynamics of yeast abundance in the galls was significantly different from that of the epiphytic yeast communities. Maximum numbers of endophytic yeastcells in the galls (up to 104 CFU/g) were comparable to abundance of epiphytic yeasts. A total of 14 species of endophytic yeasts were isolated from galls of different plants. Ascomycetous yeasts were found to predominate in the insect galls on willows and oak, while basidiomycetous yeasts dominated in mite galls on linden and elm, as well as on plant leaves. These results indicate that gall formation may be considered not only as abidirectional pathological process of the interaction between plants and invertebrates, but also as a process in which the endophytic microbial population of the galls plays an important role.

Survival of bifidobacteria and preservation of their morphological characteristics after 12-month storage of lyophilized cells was studied for the strains of Bifidobacterium bifidum and B. animalis isolated and maintained in the microbial collection of the Department of Microbiology, Moscow State University. A combined approach to pre-lyophilization treatment of microorganisms and subsequent storage was developed in order to improve cell survival. Compared to the standard cryoprotector concentrations, sucrose and glucose (5% and higher) in skim milk, as well as freezing at ‒70°C with subsequent storage at the same temperature resulted in improved survival of bifidobacteria. Under such conditions, the number of viable cells (CFU) after 12 months of storage was two to three orders of magnitude higher than in the case of the standard lyophilization procedure. Investigation of dynamics of resistance of reactivated clones to such gastrointestinal stress factors as gastric juice and bile acids revealed preservation of these properties at all storage modes. However, since the number of surviving cells decreased during storage according to the standard procedure, the number of stress-affected cells was correspondingly lower. Reactivated cultures exhibited high resistance to oxygen, with survival decreasing to 35% of the initial level.

Dynamics of the taxonomic structure of epiphytic bacterial communities of the rhizosphere and phyllosphere of seven weed species was studied. The major types of isolated organisms were identified using phenotypic and molecular biological approaches. Dispersion analysis revealed that the ontogenesis stage and plant organ were the factors with the greatest effect on the taxonomic structure of the communities. The dominantmicroorganisms of weeds were similar to those of cultivated plants. The minor components revealed in the spectra of bacterial communities of weeds belonged to poorly studied genera of chemolithotrophic proteobacteria.

The system of the green microalgal order Protosiphonales (Chlorophyceae, Chlorophyta) constructedbased on morphological, ecological, and molecular genetic data is considered. Subdivision of theorder (=macroclade Stephanosphaerinia) into four groups is proposed, with three probably corresponding tothe families Stephanosphaeraceae, Chlorococcaceae, and Protosiphonaceae and the fourth having an indefinitestatus. The diagnostic characteristics of the families, genera, and species are discussed, as well as the independentrank of some taxa. Morphological descriptions of a number of species are supplemented. Based onpolyphasic approach, strain ACSSI 23 is proposed as a candidate for a new genus and species.

The preservation of activity of extracellular enzymes in soil is presently associated with their immobilization on organic or inorganic carriers. Enzyme immobilization results, however, in a significant decrease in enzymatic activity. In the present work, the mechanism responsible for promotion of the catalytic activity was revealed, as well as the favorable effect of low-molecular alkylhydrozybenzenes of the class of alkylresorcinols, which are common in soil organic matter, on stability of immobilized enzymes (exemplified by amylases) by their post-translational modification. Optimal conditions (enzyme to sorbent ratio, pH optimum, CaCl2 concentration, and sorption time) for amylase sorption on a biological sorbent (yeast cell walls) were determined and decreased activity of the immobilized enzyme compared to its dissolved state was confirmed. Alkylresorcinols (C7AHB) at concentrations of 1.6 to 80 mM were found to cause an increase of amylase activity both in the case of already sorbed enzymes (by 30%) and in the case of a free dissolved enzyme with its subsequent immobilization (by 50–60%). In both cases, the optimal C7AHB concentration was16 mM. Amylase stability was determined for C7AHB-modified and unmodified enzymes immobilized on the biological sorbent after two cycles of freezing (–20°C) and thawing (4°C). Inverse dependence was revealed between increasing stability of C7AHB-modified enzymes and an increase in their activity, as well as higher stability of immobilized modified amylases than of the dissolved modified enzyme. Investigation of the effect of C7HOB-modification in the preservation of activity in immobilized amylases after four freeze–thaw cycles revealed: (1) better preservation of activity by the modified immobilized enzymes compared to immobilized ones; (2) differences in the dynamics of activity loss within compared pairs, with activity ofimmobilized amylases decreasing after the second cycle to a lower level (42%) than activity of the modified immobilized enzymes after the fourth cycle (48%). These results demonstrate that in the preservation of activity of extracellular enzymes in soil both stabilization mechanisms are of importance: immobilization on organic carriers and modification of the enzyme conformation by low-molecular compounds with the functions of chemical chaperones.