[Sizes of bacterial cells in soils determined by cascade filtration technique].

This paper studies the number of bacteria in typical chernozem and mountain-meadow soil by the traditional method and the cascade filtration technique. The total number of bacteria in these soils, which was obtained in filters of different diameters during filtering the suspension of a certain amount, is 1.5-5 times higher than that obtained by the traditional method. In the structure of the bacterial biomass in both soils, the biomass of bacterial cells with a diameter of 0.38-0.43 microm was dominating by 8-90%. In the typical chernozem, the biomass of cells with a diameter of 0.17 microm was slightly more than 1%; in the mountain-meadow soil, the percentage of the biomass of cells with a diameter of 0.17 microm increased by 5%. The average volume and diameter of the bacteria in the studied soils were calculated. In typical chernozem, the average volume of bacterial cells was equal to 0.0046 microm3 and the diameter was 0.206 microm. In the mountain-meadow soils, these values were slightly lower, 0.0038 microm3 and 0.194 microm, respectively. The biomass of the bacterial cells, which is usually calculated based on the cell volume of 0.1 microm3, is overestimated by about five times when counting the number on the filters. The percentage of the real biomass of soil bacteria is traditionally much lower than that estimated.

[Fungal to bacterial biomass ratio in the forest soil profile].

The carbon content in microbial biomass (Cmic-BM) was determined in various horizons of the soil profile (sod-podzo, gray, podzol, and rzhavozem) of various forests (oak, spruce Yellow Archangel, spruce moss, aspen, spruce broadleaf) in the southern taiga of European Russia (Moscow and Kaluga oblasts) by the substrate induced respiration (SIR) and direct microscopy (DM) methods. The fungi-to-bacteria ratio was measured by the selective inhibition technique and DM. A quantitative differentiation of the fungal mycelium was suggested. The Cmic-DM/Cmic-SIR in various horizons of the soil profile was about 98%. The fungal contribution to MB was 52-74% and 92-99% according to the SIR and DM data, respectively. The microbial parameters were associated with the CO2 and N2O production by the soils. The contradictory data about the fungi proportion in the MB of soils of various ecosystems were discussed.

[Comparative assessment of soil microbial biomass determined by the methods of direct microscopy and substrate-induced respiration].

The content of microbial biomass (MB) was determined in samples of gray forest, chestnut, and tundra soils with different physicochemical properties (0.4-22.7% Corg; 8.4-26.8% silt particles; pH 4.3-8.4) by the methods of substrate-induced respiration (MB(SIR)) and direct microscopy (MB(M)). The samples of two upper soil layers, 0-5 and 5-10 cm (without plant litter), from different ecosystems (forest, forest shelter belt, meadow, fallow, and arable land) and elements of relief of interfluvial tundra (block/upper land plateau, depression between blocks) have been analyzed. The content of microbial biomass in the 0-5-cm soil layer was 216-8134 and 348-7513 microg C/g soil as measured by the methods of substrate-induced respiration and direct microscopy, respectively. The MB(SIR) and MB(M) values closely correlated with each other: r = 0.90 and 0.74 for 0-5 and 5-10 cm, respectively. The average MB(SIR)/MB(M) ratio was 90 and 60% for 0-5 and 5-10 cm, respectively. The portion of microbial carbon in total organic soil carbon was, on average, 4 and 3% (SIR) and 5 and 7% (direct microscopy) for 0-5 and 5-10 cm, respectively. Possible reasons for the differences between MB(SIR) and MB(M) values in the soils under study are discussed.

[Estimation of abundance dynamics of gram-negative bacteria in soil].

Bacterial succession in soil was studied for two variants of initiation (moistening and moistening with addition of glucose). To determine the numbers of viable gram-negative bacteria, the modified nalidixic acid method was applied. The numbers of gram-negative bacteria revealed by this method were 2 to 3.5 times higher than those determined by the traditional method. In a developing community, the highest total bacterial numbers were observed on day 7; afterwards their numbers decreased and stabilized at a level exceeding four- to fivefold the initial one. In both experimental variants, the highest numbers of viable gram-negative bacteria were revealed on day 15 (75-85% of the total bacterial numbers). Morphology of these bacteria suggests their classification as cytophagas (chitinophagas) utilizing chitin from the dead fungal mycelium.

[Succession of chitinolytic microorganisms in chernozem soil].

The chitinolytic prokaryotic and eukaryotic microbial complex of chernozem soil has been investigated in the course of a succession initiated by the introduction of chitin and humidification. The dynamics of the cell numbers of chitinolytic microorganisms and of their biomass was assessed by fluorescent microscopy and by inoculation of selective media. Emission of carbon dioxide and nitrous oxide, as well as dinitrogen fixation, was assessed by gas chromatography. It was found that, when the succession was initiated by the introduction of both chitin and humidification, it resulted in greater cell numbers and biomass of chitinolytic microorganisms and higher levels of CO2 and N2O emission and of nitrogen fixation than when the succession was initiated by humidification alone. As compared to the control samples, a significant (twofold) increase in the prokaryote cell number and biomass was found on the fourth day of the succession initiated by humidification and introduction of chitin. One week after the initiation of succession, the fungal biomass and length of mycelium were twice as high as those in the control samples. These results led to the conclusion that chitin utilization in chernozem soil starts during the initial stages of succession and is performed by both prokaryotic and eukaryotic microorganisms.

[137Cs distribution and accumulation in the tissues of cultivated fungi (Pleurotus ostreatus)].

The authors examined 137Cs accumulation and distribution in different structures and tissues of Pleurotus ostreatus cultivated under laboratory conditions. The fungi were shown to concentrate 137Cs. A higher concentrations of the radionuclides in the fungi compared to their substrate is manifested at the first stages of the fruit body formation, the maximum content of 137Cs is accumulated by fungi in the middle of bearing stage. The fungus tissues are different by their accumulative capacity as follows (ascending range): central, more dense part of the stipe < stipe < mycelium < cap < generative tissues. 137Cs accumulation in the fruit bodies depends also on the fungus size and age.

[Germination of phytopathogenic fungi conidia]. / Zakonomernosti prorastaniia konidii fitopatogennykh gribov.

The autoregulation of conidium germination in phytopathogenic micromycetes of the genera Fusarium, Botrytis, and Bipolaris was studied. It was shown that Trichoderma longibrachiatum was less competitive than Fusarium oxysporum after their simultaneous inoculation but inhibited the phytopathogen growth in the case of earlier introduction. In the latter case, no autoinhibition of the germination of F. oxysporum conidia occurred; moreover, cooperative effect was observed, i.e., the number of germinated F. oxysporum conidia increased with an increase in their density.

[Autoregulation of conidium germination in micromycetes of the genus Trichoderma]. / Autoreguliatsiia prorastaniia konidii mikromitsetov roda Trichoderma.

The amount of germinated conidia of microcytes belonging to the genus Trichoderma considerably decreased with an increase in the population density. Strains exhibited different ecological strategies. The maximum number of germinated conidia (30-70%) was recorded when the average distance between conidia was 50 microns.

[A chitinolytic actinomycete complex in black soil]. / Khitinoliticheskii aktinomitsetnyi komplex chernozema.

A chitinolytic actinomycete complex in chernozem soil has a specific taxonomic composition, which differs from that of the actinomycete complex which is typically isolated on standard nutrient media containing sugars and organic acids as carbon sources. The actinomycete complex that was isolated by using nutrient media with chitin as the source of carbon and nitrogen was dominated by representatives of the genus Streptosporangium, and the actinomycete complex that was isolated by using nutrient media with sugars and organic acids as the carbon sources was dominated by representatives of the genus Streptomyces. The confirmation to the ability of actinomycetes to utilize chitin as a sole source of carbon and nitrogen came from the augmented length and biomass of the mycelium, the increased number and biomass of the actinomycete spores, the production of carbon dioxide, and the accumulation of NH4+ ions in the culture liquid of the actinomycetes that are grown in the nutrient media with chitin.

[The quantity and structure of the root-associated microbial complexes of two greenhouse rose cultivars]. / Chislennost' i struktura mikrobnykh kompleksov kornevykh sistem teplichnykh roz.

The study of the root-associated microbial complexes of affected and healthy rose plants of two cultivars (Grand gala and Royal velvet) grown in a greenhouse showed that the biomass of eukaryotic microorganisms in the rhizoplane and rhizosphere of healthy rose plants and in the surrounding soil was considerably lower than in the same loci of affected plants. In contrast, the biomass of root-associated prokaryotic microorganisms was higher in the case of healthy than in the case of affected rose plants. The root-associated bacterial complexes of both affected and healthy rose plants were dominated by the genera Arthrobacter, Rhodococcus, and Myxobacterium and did not contain phytopathogenic bacteria. The root-associated fungal complex of healthy roses was dominated by fungi of the genus Trichoderma, whereas that of the affected rose plants was dominated by the species Aureobasidium microstictum. The affected cane cuttings and cankers occurring on affected canes were found to contain Coniothyrium fuckelii (the causal fungus of rose stem canker) and sclerotia of Botrytis cinerea (the causal fungus of gray rot). The micromycete complex of healthy rose plants was not so diverse as was the micromycete complex of affected rose plants.

[New criteria for evaluation of soil bacterial complexes]. / Novye kriterii dlia otsenki spetsifiki bakterial'nykh kompleksov razlichnykh pochv.

The initial concentration of prokaryotic microorganisms, the type of their growth, doubling time, and the growth dynamics of bacteria and actinomycetes in three types of soil (meadow, chestnut, and soddy forest) were evaluated by the luminescence microscopic analysis of soil samples incubated in a humid chamber for 1 day. Soddy forest and chestnut soils differed in most of the parameters analyzed. Meadow soil was close to soddy forest soil in some parameters and to chestnut soil in other parameters. All soil suspensions exhibited high growth rates of bacteria and actinomycetes, indicating that the fraction of viable microorganisms in the soils was high.

[The growth-promoting effect of Beijerinckia and Clostridium sp. cultures on some agricultural crops]. / Stimuliatsiia rosta rastenii kul'turami Beijerinckia i Clostridium.

New strains of Beijerinckia mobilis and Clostridium sp. isolated from the pea rhizosphere were studied with respect to their promoting effect on the growth and development of some agricultural crops. Seed soaking in bacterial suspensions followed by the soil application of the suspensions or their application by means of foliar spraying was found to be the most efficient method of bacterization. The application of B. mobilis and Clostridium sp. cultures in combination with mineral fertilizers increased the crop production by 1.5-2.5 times. The study of the population dynamics of B. mobilis by the method of genetic marking showed that this bacterium quickly colonized the rhizoplane of plants and, therefore, had characteristics of an r-strategist. At the same time, Clostridium sp. was closer to K-strategists, since this bacterium slowly colonized the econiches studied. The introduction of the bacteria into soil did not affect the indigenous soil bacterial complex. The presence of Clostridium sp. slowed down the colonization of roots by the fungal mycelium. The possible mechanisms of the plant growth-promoting activity of B. mobilis and Clostridium sp. are discussed.

[The effect of tillage and mesoreief on the structure of soil microbial biomass]. / Vliianie okul'turivaniia i mezorel'efa na strukturu mikrobnoi biomassy pochv.

The investigation of soil microbial cenoses in cultivated catenas and in virgin soils at the foot of catenas showed that the structure of these microbiocenoses depends on the type of the vegetation cover, the characteristics of mesorelief, and the degree of soil tillage. The microbiocenoses were found to be dominated by the fungal mycelium. The proportion of bacteria and fungal spores was higher and the seasonal variations in the soil microbial communities were more distinct in the cultivated than in the virgin swamp and forest soils. The type of mesorelief was found to appreciably influence microbial populations in the top humus-rich horizons of the cultivated soils and not in the mineral soil horizons.

[Features of microorganism distribution in the Al-Fe-humus podzol of the northern-taiga spruce forests: natural and technogenic aspects]. / Osobennosti rasprostraneniia mikroorganizmov v Al-Fe-gumusovykh podzolakh severo-taezhnykh elovykh lesov: prirodnye i tekhnogennye aspekty.

Natural and anthropogenically induced seasonal variations in the abundance and biomass of various groups of microorganisms in the Al-Fe-humus podzols of boreal spruce forests were analyzed. The fungal biomass in these soils was found to be considerably higher than the bacterial biomass. Microbial population was mainly concentrated in a thin surface layer (10-15 cm in thickness), which included the forest litter and the upper mineral root-inhabited soil horizon and greatly differed from other soil horizons in morphology and other properties. This layer was found to be optimal with respect to hydrothermal and nutritional conditions and was characterized by profound seasonal variations in the abundance and biomass of microbiota. The high acidity, typical of the Al-Fe-humus podzols, resulted from the metabolism of their microbial communities. In the polluted podzols, the population of prokaryotes increased and that of eukaryotes decreased.

[Effect of oil on the size of number, biomass, and viability of fungi in highmoor peats]. / Bliianie nefti na chislennost', biomassu i zhiznesposobnost' gribov v verkhovykh torfianikakh.

Some microbiological parameters, such as the fungal mycelium length, the number of fungal spores, the distribution profiles of micromycetes, the viability of fungal propagules, the length distribution of micromycete hyphae, and the proportion between fungal spores and yeastlike cells, can be used to determine the degree of soil contamination with oil and the concentration that is inhibitory to the micromycete complexes of highmoor peats.

[Microsampling of rhizosphere soil and laboratory artefacts]. / Mikronaveski rizosfernoi pochvy i laboratornye artefakty.

A parallel analysis of the microsamples of surrounding soil and microsamples of rhizosphere soil did not reveal the so-called rhizospheric effect. The data obtained showed that dilution significantly influences the results of determination of the number of soil microorganisms. The actual number of microorganisms revealed in soil samples greatly differed from the theoretically predicted values. The enumeration of microorganisms in soil microsamples by direct count and, especially, by the plating method with the use of conversion coefficients based on the degree of sample dilution gave erroneous results.

[Effect of phosphorus on the colonization of barley rhizosphere by microorganisms]. / Vliianie fosfora na kolonizatsiiu mikroorganizmami prokornevoi zony iachmenia.

The mineral phosphorus supply produced two outbreaks in the bacterial population of the barley rhizosphere and rhizoplane but inhibited the growth of fungal mycelium. The inhibition of mycelial growth might be due to the exudation of specific inhibitors by barley roots, since the most pronounced inhibition was observed at high doses of supplementary phosphorus.

[Dynamics of populations of microbial antagonists in nonsterile soil]. / Dinamika populiatsii mikrobov antagonistov v nestril'noi pochve.

The interaction between populations was studied with Arthrobacter crystallopoietes and Streptomyces olivocinereus, an actinomycete producing the antibiotic heliomycin active against Gram-positive microorganisms. The two organisms were either cultivated together in a growth medium or the two populations were introduced simultaneously into nonsterile soil at different levels of population density. The antagonism was found in both cases: A. crystallopoietes cells died off when a population of the potential antagonist was added. The density of a population producing the antibiotic had to be sufficiently high for the antagonism to be manifested. The antagonism influenced the dynamics of a population of the antibiotic-sensitive microorganism. The results have confirmed earlier data to the effect that antibiotic synthesis is possible in nonsterile soil.

[Relationship between the dynamics of the numbers of nodule bacteria in the soil and the stage of microbial succession]. / Zavisimost' dinamiki chislennosti kluben'kovykh bakterii v pochve ot stadii mikrobnoi suktsessii.

The survival of a population of nodule bacteria after its introduction into soil depends on the ratio between favourable and unfavourable microzones. This ratio does not remain constant in one and the same soil at different stages of microbial succession even if the succession is caused by simple humidification of the soil without any introduction of additional substrates. The dynamics of the incidence of nodule bacteria introduced, at one and the same level, into soil samples of different growth stages of a complex of soil microorganisms significantly differed. Successful nitragination may be assisted by determining the growth stage of a microbial system when the population is being introduced and by changing the environment in the soil.

[Dynamics of the development of different microorganisms in soil]. / Dinamika razvitiia razlichnykh mikroorganizmov v pochve.

The dynamics of individual components from the complex of soil microorganisms (bacteria, fungi, actinomycetes) and the population of Stm. olivocinereus introduced into soil was studied by luminescent microscopy and inoculation. The population density maxima for individual components from the complex of soil microorganisms were shown to be separated in time suggesting a succession. Fungi developed at the first steps of succession and dominated in biomass over the remaining components of the complex. Bacteria and actinomycetes developed at the later steps of succession. Glucose addition stimulated still earlier growth of fungi (the maximal mycelium legth was registered by the second day) but had hardly any effect on the dynamics of other components of the complex.