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PubMed2003

Community structure of ammonia-oxidizing bacteria within anoxic marine sediments.

The potential for oxidation of ammonia in anoxic marine sediments exists through anaerobic oxidation by Nitrosomonas-like organisms, utilizing nitrogen dioxide, coupling of nitrification, manganese reduction, and anaerobic oxidation of ammonium by planctomycetes (the Anammox process). Here we describe the presence of microbial communities with the potential to carry out these processes in a natural marine sediment system (Loch Duich, Scotland). Natural microbial communities of Planctomycetales-Verrucomicrobia and beta- and gamma-proteobacterial ammonia-oxidizing bacteria were characterized by analysis of 16S rRNA genes amplified using group-specific primers by PCR- and reverse transcription-PCR amplification of 16S rDNA and RNA, respectively. Amplification products were analyzed by sequencing of clones and by denaturant gradient gel electrophoresis (DGGE). Amplification of primers specific for Planctomycetales-Verrucomicrobia and beta-proteobacterial ammonia-oxidizing bacteria generated products at all sampling sites and depths, but no product was generated using primers specific for gamma-proteobacterial ammonia-oxidizing bacteria. 16S rDNA DGGE banding patterns indicated complex communities of beta-proteobacterial ammonia-oxidizing bacteria in anoxic marine sediments. Phylogenetic analysis of sequences from clones and those excised from DGGE gels suggests dominance of Nitrosospira cluster 1-like organisms and of strains belonging to a novel cluster represented in dominant bands in 16S rRNA DGGE banding patterns. Their presence indicates a group of organisms closely related to recognized beta-proteobacterial ammonia-oxidizing bacteria that may be selected in anoxic environments and may be capable of anoxic ammonia oxidation. Sequence analysis of planctomycete clone libraries and sequences excised from DGGE gels also demonstrated a diverse microbial community and suggested the presence of new subdivisions, but no sequence related to recognized Anammox organisms was detected.

Ammonia↗
PubMed2005

The impact of saponins or saponin-containing plant materials on ruminant production--a review.

Saponins are steroid or triterpene glycoside compounds found in a variety of plants. Some saponin-containing plants, mainly legumes, have been used as animal feed, but others are toxic. Several studies on the effect of saponins on ruminant production have also been reported. Some in vitro and in vivo experiments that demonstrate the beneficial effects of saponin such as defaunation of the rumen and manipulation of the end products of fermentation are described. Defaunation is the selective removal of protozoa from the rumen microbial ecosystem by a cell membrane cholesterol-saponin interaction, which causes cell rupture. Because protozoa in the rumen cause protein turnover by predating on bacteria, defaunation increases the nitrogen utilization of the ruminant and may lead to an increase in growth, milk, or wool production. The growth-promoting effect was evident in the high roughage diet suggesting that the application of saponins or saponin-containing plant materials may be beneficial for the subsistence farmers in developing countries. Saponins are deglycosylated by rumen microbes. Some sapogenins have been detected in the digestive tract of ruminants; however, the direct action of these compounds on the host animal is still unclear. No information on the effects of saponin on ruminant reproduction is available. There is an urgent need for a systematic evaluation of the most active structural components of the saponins, and their interaction with the microbial community, the host animal, and the diet. Along with these studies, the direct effects of saponins or their microbial degradation products on the host must be examined in order to get the full understanding of the metabolism and beneficial effects of saponins on animals.

Animals↗
PubMed1975

Relationship between ruminal ammonia and nonprotein nitrogen utilization by ruminants. II. Application of published evidence to the development of theoretical model for predicting nonprotein nitrogen utilization.

Results from published experiments dealing with several aspects of nitrogen utilization by ruminants were used to test the concept of zero utilization of nonprotein nitrogen under conditions where more ammonia (greater than 5 mg ammonia nitrogen/100 ml) is in the rumen than can be converted to microbial protein. Results from experiments where the flow of non-ammonia nitrogen to the abomasum of sheep was measured indicate that when urea was the source of supplemental nitrogen, a constant quantity of amino acids reached the abomasum for all rations ranging from 10 to 23% crude protein. From growth studies, addition of nonprotein nitrogen to low protein, high energy rations caused an improved rate of gain. Additions of nonprotein nitrogen to rations resulting in predicted ruminal ammonia concentrations greater than 5 mg ammonia nitrogen/100 ml rumen fluid were without benefit. From lactation studies, nonprotein nitrogen supplementation did not improve milk production if the ration contained more than 12.5% crude protein prior to supplementation or if the predicted ruminal ammonia concentration was greater than 4 mg ammonia nitrogen/100 ml rumen fluid. The importance of the amino acid requirement of the animal as well as the composition of the ration in designing and evaluating nitrogen supplementation studies is discussed.

Ammonia↗
PubMed1976

Dynamics of fermentation of a purified diet and microbial growth in the rumen.

Ruminal fermentation and disappearance of glucose, starch, and cellulose, and incorporation of glucose and starch into microbial cells were estimated in a fistulated Jersey cow fed twice daily a purified diet containing urea as the sole nitrogen source. Estimated rumen volume was 59.8 liters. Turnover time and rate of passage of rumen contents were 33.4 h and 1.8 liters per h. Turnover times of glucose, starch, and cellulose were .17, 4.7, and 14.2 h. Fermentation times of glucose, starch, and cellulose were .17, 5.5, and 25.1 h. Percentages of glucose, starch, and cellulose utilized in the rumen were 99.4, 85.4, and 60.6. Thus, 18.5% of the carbohydrate fed bypassed rumen fermentation, and 81.5% was utilized in the rumen. All glucose disappeared from the rumen within an hour. An average of 32.1, 43.0, and 14%, respectively, of glucose utilized was incorporated into microbial cells, volatile fatty acids, and carbon dioxide. Percentage of starch incorporated into cells varied, with time being highest 2 h after feeding at 40% and lowest at 20%, 10 h after feeding. Respective percentages of starch incorporated into microbial cells, volatile fatty acids, and carbon dioxide were 32.4, 45.9; and 13.3. Total microbial protein and cell yields per kilogram carbohydrate utilized in the rumen were 77.1 and 117.5 g. Microbial cell yield per mole (estimated) of adenosine triphosphate was 16.2 g.

Adenosine Triphosphate↗
PubMed2004

Characteristics of neutralization of acids by newly isolated fungal cells.

Soil microorganisms play an important role in maintaining soil pH at levels suitable for other soil organisms. To clarify the biological neutralization mechanism in soil, we isolated soil microorganisms showing a high ability to neutralize acids and studied their characteristics. From our taxonomic study, three isolated strains were identified as filamentous fungi, namely Mucor sp., Aspergillus fumigatus, and Aureobasidium pullulans. These strains could secrete basic materials, such as ammonia, for neutralization, grow in the medium at pH 4.0 and increase the pH of the medium to approximately 8.0. These microbial cells could neutralize not only nitric acid but also sulfuric and hydrochloric acids. The strains could also grow by utilizing nitric acid as a sole nitrogen source. In the soil containing these organisms, the pH was maintained in the neutral range by the buffering action of basic materials that they secrete. These results suggest that these fungal cells are useful for protecting the soil from acidification by acid rain.

Journal Article↗
PubMed1993

Microbial metabolism of quinoline and related compounds. XIX. Degradation of 4-methylquinoline and quinoline by Pseudomonas putida K1.

A bacterial strain, designated K1, which utilizes 4-methylquinoline and quinoline as sole source of carbon, nitrogen and energy was isolated from soil. Based on its morphological and physiological characteristics, it was classified as Pseudomonas putida biovar B. Four metabolites of 4-methylquinoline degradation were isolated from the culture supernatant and identified as 4-methyl-2-oxo-1,2-dihydroquinoline, 8-hydroxy-4-methyl-2-oxo-1,2-dihydroquinoline, 7,8-dihydroxy-4-methyl-2-oxo-1,2-dihydroquinoline and 6-hydroxy-5-(2-carboxyethenyl)-4-methyl-1H-2-pyridone. Formation of the latter compound is suggested to proceed by decarbonylation of a putative meta-cleavage product of the 7,8-dihydroxy derivative. During growth on quinoline four compounds were released into the culture fluid, too. Upon isolation they were identified as 2-oxo-1,2-dihydroquinoline, 6-hydroxy-2-oxo-1,2-dihydroquinoline, 5-hydroxy-6-(3-carboxy-3-oxopropenyl)-1H-2-pyridone and 2H-pyran-2-on-[3,2b]-5H-6-pyridone. Thus it is proved, that Pseudomonas putida possesses two different catabolic pathways for various quinoline derivatives, which are induced selectively depending on the growth substrate.

Biotransformation↗
PubMed1999

Effect of three strains of Pleurotus tuber-regium (Fr.) Sing. on chemical composition and rumen fermentation of wheat straw.

This study was conducted to investigate changes in in vitro dry matter digestibility (IVDMD) and cell wall constituent degradation in wheat straw treated with 3 strains of the fungus Pleurotus tuber-regium (PT). The incubation of wheat straw for 30 days at 28 degrees C improved IVDMD from 30.3% (UWS-untreated wheat straw) to 47.1% for strain PT1, to 48.5% for PT4, and was unchanged IVDMD-29.9% -for PT5. The growth of fungi was accompanied by the dry matter loss of wheat straw: 31.5% for PT1, 20.9% for PT4, and 4.8% for PT5. Fungal treatment was characterized by increased crude protein and ash contents (%) in all fungi-treated straws and reduced hemicellulose and lignin content. It is evident that enzymes of all 3 PT strains preferentially degraded hemicellulose and lignin over cellulose. Wheat straw treated with PT1 (TWS-PT1), PT4 (TWS-PT4), and PT5 (TWS-PT5) and barley (80% : 20%) were used as the experimental diets at the fermentation in the artificial rumen. UWS with barley (80% : 20%) served as the control diet. The fermentation of experimental diets was accompanied with increased IVDMD and a very low degree of hemicellulose degradation. Total gas and methane productions were similar in all diets. Moreover, total volatile fatty acid (VFA) production (mmol day(-1)), mol % of acetate, propionate, butyrate, isobutyrate, and isovalerate were not influenced during the fermentation of experimental diets. From the stoichiometric relations, production, utilization, and recovery of metabolic hydrogen and organic matter fermented were unchanged. Only the recovery of metabolic hydrogen in TWS-PT5 was significantly increased in comparison to control diet. Total microbial production showed the tendency of lower values in experimental diets, and it was accompanied with a significant decrease of ammonia nitrogen (mg L(-1)). Finally the results showed that the strains of Pleurotus tuber-regium can improve the quality of wheat straw, but the loss of dry matter (DM) (mainly hemicellulose) limits the effective utilization of fungi-treated straw in ruminant digestion.

Journal Article↗
PubMed1984

Microbial metabolism of 1,2-propanediol studied by the Rumen Simulation Technique (Rusitec).

A series of experiments with the Rumen Simulation Technique (Rusitec) showed that 1,2-propanediol was metabolized efficiently by rumen micro-organisms and that the main end-products of fermentation were propionic and 2-methylbutyric acids. Propionaldehyde and n-propanol were also formed as intermediate compounds. The effect of the diol on digestion of the basal diet appeared to be small with concentrate, or when the roughage was supplemented with additional nitrogen (urea). The decrease in the output of acetic and butyric acids was consistent with utilization of C2 units for synthesis of 2-methylbutyric acid. The fermentation of 1,2-propanediol resulted in little or no increase in the output of additional microbial matter. The distribution of radioactivity from [1-14C]1,2-propanediol confirmed that propionaldehyde and n-propanol were the primary products of metabolism of the diol and that the end-products were propionic and 2-methylbutyric acids, with very little labelling of microbial matter. Between 2% and 3% of radioactivity was found in gases and surprisingly the specific radioactivity of methane was higher than that of carbon dioxide, particularly during the initial stages of incubation. Possible pathways in the degradation of 1,2-propanediol by rumen micro-organisms are suggested and discussed in relation to similar reactions established in other systems.

Acyl Coenzyme A↗
PubMed2003

A combined mass and energy balance to provide bioindicators of soil microbiological quality.

In this work, a method is proposed to quantify the efficiency of carbon utilization by soil microbes. Microcalorimetry was used to compute the heat yield (Y(Q/X)) of six soil samples collected in the Amazon. A combined mass and energy balance is developed to quantify the enthalpy of the glucose oxidation reaction (Delta(r)H(s)) and the biomass yield (Y(X/S)) from the experimental values of Y(Q/X). Results were compared by graphical analysis to establish the kinetics of the glucose oxidation and the microbial growth reactions in terms of energy dissipation. The correlations found suggest that the measured values for Y(Q/X) and Delta(r)H(s) are biomass yield dependent. The main environmental factors affecting the kinetics of the glucose oxidation and the microbial growth reactions in soils are the initial microbial population and the percentage of nitrogen of the samples. The comparative study among the samples showed that the deforestation of the Primary forests in the Amazon to establish arable lands, affected the efficiency of the carbon utilization by soil microorganisms.

Bacteria↗
PubMedDate not supplied

[Diazotrophs in the digestive tract of termite Neotermes castaneus].

Normal vital activity of termites Neotermes castaneus requires the presence and continuous replenishment of transient nitrogen-fixing bacteria in their digestive tract, which is realized by coprophagy and repeated utilization of substrate enriched in termite feces. This is the first demonstration of significant changes in the complex of aerobic and facultatively anaerobic nitrogen fixers mediated by an extension of microbial group composition and a shift in dominant taxa in termites that cannot reutilize their feces.

Animals↗
PubMed2005

[Engineering issues of microbial ecology in space agriculture].

Closure of the materials recycle loop for water-foods-oxygen is the primary purpose of space agriculture on Mars and Moon. A microbial ecological system takes a part of agriculture to process our metabolic excreta and inedible biomass and convert them to nutrients and soil substrate for cultivating plants. If we extend the purpose of space agriculture to the creation and control of a healthy and pleasant living environment, we should realize that our human body should not be sterilized but exposed to the appropriate microbial environment. We are proposing a use of hyper-thermophilic aerobic composting microbial ecology in space agriculture. Japan has a broad historical and cultural background on this subject. There had been agriculture that drove a closed loop of materials between consuming cities and farming villages in vicinity. Recent environmental problems regarding garbage collection and processing in towns have motivated home electronics companies to innovate "garbage composting" machines with bacterial technology. Based on those matured technology, together with new insights on microbiology and microbial ecology, we have been developing a conceptual design of space agriculture on Moon and Mars. There are several issues to be answered in order to prove effectiveness of the use of microbial systems in space. 1) Can the recycled nutrients, processed by the hyper-thermal aerobic composting microbial ecology, be formed in the physical and chemical state or configuration, with which plants can uptake those nutrients? A possibility of removing any major components of fertilizer from its recycle loop is another item to be evaluated. 2) What are the merits of forming soil microbial ecology around the root system of plants? This might be the most crucial question. Recent researches exhibit various mutually beneficial relationships among soil microbiota and plants, and symbiotic ecology in composting bacteria. It is essential to understand those features, and define how to conduct preventive maintenance for keeping cultivating soil healthy and productive. 3) Does microbial ecology contribute to building sustainable and expandable human habitation by utilizing the on site extraterrestrial resources? We are assessing technical feasibility of converting regolith to farming soil and structural materials for space agriculture. In the case of Mars habitation, carbon dioxide and a trace amount of nitrogen in atmosphere, and potassium and phosphor in minerals are the sources we consider. Excess oxygen can be accumulated by woods cultivation and their use for lumber. 4) Is the operation of space agriculture robust and safe, if it adopts hyper-thermophilic aerobic microbial ecology? Any ecological system is complex and non-linear, and shows latency and memory effects in its response. It is highly important to understand those features to design and operate space agriculture without falling into the fatal failure. Assessment should be made on the microbial safety and preparation of the preventive measures to eliminate negative elements that would either retard agricultural production or harm the healthy environment. It is worth to mention that such space agriculture would be an effective engineering testbed to solve the global problem on energy and environment. Mars and Moon exploration itself is a good advocate of healthy curiosity expressed by the sustainable civilization of our humankind. We propose to work together towards Mars and Moon with microbial ecology to assure pleasant habitation there.

Agriculture↗
PubMed2006

Microbial diversity and bioremediation of a hydrocarbon-contaminated aquifer (Vega Baja, Puerto Rico).

Hydrocarbon contamination of groundwater resources has become a major environmental and human health concern in many parts of the world. Our objectives were to employ both culture and culture-independent techniques to characterize the dynamics of microbial community structure within a fluidized bed reactor used to bioremediate a diesel-contaminated groundwater in a tropical environment. Under normal operating conditions, 97 to 99% of total hydrocarbons were removed with only 14 min hydraulic retention time. Over 25 different cultures were isolated from the treatment unit (96% which utilized diesel constituents as sole carbon source). Approximately 20% of the isolates were also capable of complete denitrification to nitrogen gas. Sequence analysis of 16S rDNA demonstrated ample diversity with most belonging to the infinity, beta and gamma subdivision of the Proteobacteria, Bacilli, and Actinobacteria groups. Moreover, the genetic constitution of the microbial community was examined at multiple time points with a Functional Gene Array (FGA) containing over 12,000 probes for genes involved in organic degradation and major biogeochemical cycles. Total community DNA was extracted and amplified using an isothermal phi29 polymerase-based technique, labeled with Cy5 dye, and hybridized to the arrays in 50% formimide overnight at 50 degrees C. Cluster analysis revealed comparable profiles over the course of treatment suggesting the early selection of a very stable microbial community. A total of 270 genes for organic contaminant degradation (including naphthalene, toluene [aerobic and anaerobic], octane, biphenyl, pyrene, xylene, phenanthrene, and benzene); and 333 genes involved in metabolic activities (nitrite and nitrous oxide reductases [nirS, nirK, and nosZ], dissimilatory sulfite reductases [dsrAB], potential metal reducing C-type cytochromes, and methane monooxygenase [pmoA]) were repeatedly detected. Genes for degradation of MTBE, nitroaromatics and chlorinated compounds were also present, indicating a broad catabolic potential of the treatment unit. FGA's demonstrated the early establishment of a diverse community with concurrent aerobic and anaerobic processes contributing to the bioremediation process.

Bacteria↗
PubMed2001

Microbial thiocyanate utilization under highly alkaline conditions.

Three kinds of alkaliphilic bacteria able to utilize thiocyanate (CNS-) at pH 10 were found in highly alkaline soda lake sediments and soda soils. The first group included obligate heterotrophs that utilized thiocyanate as a nitrogen source while growing at pH 10 with acetate as carbon and energy sources. Most of the heterotrophic strains were able to oxidize sulfide and thiosulfate to tetrathionate. The second group included obligately autotrophic sulfur-oxidizing alkaliphiles which utilized thiocyanate nitrogen during growth with thiosulfate as the energy source. Genetic analysis demonstrated that both the heterotrophic and autotrophic alkaliphiles that utilized thiocyanate as a nitrogen source were related to the previously described sulfur-oxidizing alkaliphiles belonging to the gamma subdivision of the division Proteobacteria (the Halomonas group for the heterotrophs and the genus Thioalkalivibrio for autotrophs). The third group included obligately autotrophic sulfur-oxidizing alkaliphilic bacteria able to utilize thiocyanate as a sole source of energy. These bacteria could be enriched on mineral medium with thiocyanate at pH 10. Growth with thiocyanate was usually much slower than growth with thiosulfate, although the biomass yield on thiocyanate was higher. Of the four strains isolated, the three vibrio-shaped strains were genetically closely related to the previously described sulfur-oxidizing alkaliphiles belonging to the genus Thioalkalivibrio. The rod-shaped isolate differed from the other isolates by its ability to accumulate large amounts of elemental sulfur inside its cells and by its ability to oxidize carbon disulfide. Despite its low DNA homology with and substantial phenotypic differences from the vibrio-shaped strains, this isolate also belonged to the genus Thioalkalivibrio according to a phylogenetic analysis. The heterotrophic and autotrophic alkaliphiles that grew with thiocyanate as an N source possessed a relatively high level of cyanase activity which converted cyanate (CNO-) to ammonia and CO2. On the other hand, cyanase activity either was absent or was present at very low levels in the autotrophic strains grown on thiocyanate as the sole energy and N source. As a result, large amounts of cyanate were found to accumulate in the media during utilization of thiocyanate at pH 10 in batch and thiocyanate-limited continuous cultures. This is a first direct proof of a "cyanate pathway" in pure cultures of thiocyanate-degrading bacteria. Since it is relatively stable under alkaline conditions, cyanate is likely to play a role as an N buffer that keeps the alkaliphilic bacteria safe from inhibition by free ammonia, which otherwise would reach toxic levels during dissimilatory degradation of thiocyanate.

Alkalies↗
PubMed2005

Use of xylan-rich cost effective agro-residues in the production of xylanase by Streptomyces cyaneus SN32.

AIM: The present study aimed at optimization of cultural and nutritional parameters for enhanced production of xylanase from Streptomyces cyaneus SN32. METHODS AND RESULTS: The xylanase production by S. cyaneus SN32 on most of the agro-residues tested in this study was more, as compared with the xylanase yield in the medium supplemented with commercial xylan. The presence of wheat bran as carbon source in the medium induced the highest production of xylanase followed by corn cob. Utilization of maize stalk, gram husk and black gram husk for microbial xylanase production has been reported first time in the present study. Among all the organic and inorganic sources of nitrogen tested in the study, peptone was found to be the best in stimulating xylanase production by S. cyaneus SN32. CONCLUSION: The production of xylanase from this thermoalkalophilic actinomycete has been enhanced 1.44-fold. To the best of our knowledge, the magnitude of enzyme yield i.e. 720 IU ml(-1) by S. cyaneus SN32 has not been reported for any other actinomycete so far. SIGNIFICANCE AND IMPACT OF STUDY: Present studies revealed that thermoalkalophilic S. cyaneus SN32, because of its simple nutritional requirements and its ability to exhibit considerably good enzyme yield, is a potent xylanase producer for its economical application in various industries.

Agriculture↗
PubMed2007

Chemistry and fate of simazine.

Simazine, first introduced in 1956, is a popular agricultural herbicide used to inhibit photosynthesis in broadleaf weeds and grasses. It is a member of the triazine family, and according to its physicochemical properties, it is slightly soluble in water, relatively nonvolatile, capable of partitioning into organic phases, and susceptible to photolysis. Sorption and desorption studies on its behavior in soils indicate that simazine does not appreciably sorb to minerals and has the potential to leach in clay and sandy soils. The presence of organic matter in soils contributes to simazine retention but delays its degradation. The primary sorptive mechanism of simazine to OM has been proposed to be via partitioning and/or by the interaction with functional groups of the sorbent. Farming practices directly influence the movement of simazine in soils as well. Tilled fields lower the runoff of simazine when compared to untilled fields, but tilling can also contribute to its movement into groundwater. Planting cover crops on untilled land can significantly reduce simazine runoff. Such practices are important because simazine and its byproducts have been detected in groundwater in The Netherlands, Denmark, and parts of the U.S. (California, North Carolina, Illinois, and Wisconsin) at significant concentrations. Concentrations have also been detected in surface waters around the U.S. and United Kingdom. Although the physicochemical properties of simazine do not support volatilization, residues have been found in the atmosphere and correlate with its application. Although at low concentrations, simazine has also been detected in precipitation in Pennsylvania (U.S.), Greece, and Paris (France). Abiotically, simazine can be oxidized to several degradation products. Although hydrolysis does not contribute to the dissipation of simazine, photolysis does. Microbial degradation is the primary means of simazine dissipation, but the process is relatively slow and kinetically controlled. Some bacteria and fungal species capable of utilizing simazine as a sole carbon and nitrogen source at a fast rate under laboratory conditions have been identified. Metabolism of simazine in higher organisms is via cytochrome P-450-mediated oxidation and glutathione conjugation.

Environmental Pollutants↗
PubMed1983

Effect of lasalocid sodium on rumen fermentation and digestion in sheep.

Four adult sheep were fed 4 diets successively according to a Latin-square design. They were fitted with a rumen cannula and with simple cannulae at the duodenum and ileum. The basal diet (L0) was composed of highly-pressed ensiled sugar beet pulp (56.2%), cereal (barley and corn: 27.6%), urea (1.5%) and wheat straw (14.1%). Lasalocid sodium was added to obtain the following respective amounts: 21 ppm for diet L1, 43 ppm for diet L2 and 64 ppm for diet L3 (table 1). In the rumen, lasalocid significantly increased the molar proportion of propionic acid in the volatile fatty acids (VFA) mixture at the expense of the acetic and butyric acid proportions. The total VFA concentration decreased, especially with 43 and 64 ppm (table 2). Accordingly, the proportion of methane in rumen gases decreased. The ciliate population was always lower in animals fed experimental diets L1, L2, and particularly L3. The non-food-particle-associated bacterial population also decreased; the differences were significant only with the highest doses of lasalocid (L3). At the same time, bacterial cellulolytic activity increased 10%, indicating that qualitative modifications had taken place in the rumen bacterial population (table 3). Overall digestive utilization of organic matter (OM) decreased when lasalocid was added to the diets. This was due to a considerable reduction in forestomach digestion (12% decrease) (table 4). A greater supply of OM rich in cell-wall carbohydrates in the duodenum would explain the lower digestibility in the small intestine of animals given diet L1 and especially the L2 and L3 diets. No significant shift in digestion was noted in the large intestine. The composition of the non-ammonia nitrogen that entered the duodenum of sheep given lasalocid differed from that noted with the control diet (L0) (table 5). The amount of microbial proteins was significantly lower, whilst the proportion of non-degraded feed proteins was higher. The efficiency of microbial synthesis (bacterial proteins/kg OM truly digested in the rumen) was not significantly modified by lasalocid. All these modifications in digestion observed with these diets, and resulting from changes in the qualitative and quantitative composition of flora and fauna in the rumen, have an effect on nitrogen and energy utilization in the ruminant.

Animals↗
PubMedDate not supplied

[Nitrogen-fixing activity in peat soils from a raised bog].

The nitrogenase (acetylene reductase) activity in monolithic and minced peat samples was found to be low, no more than 0.014-0.022 mg N/(kg h). Incorporation of the 15N2 isotope into organic compounds of peat soil was from 2.71-8.13 mg N/kg over 15 days. The nitrogen-fixing activity was the highest in a 10-20 cm layer of soil and much lower in the upper (under green moss) and deeper (20-30 cm) layers. The addition of glucose to soil samples stimulated nitrogen fixation considerably after 18-26 h. The maximum nitrogenase activity (3.5-3.8 mg N/(kg h)) observed after 60-70 h coincided with the peak of respiratory activity. A repeated addition of glucose after its exhaustion increased nitrogenase activity without a lag period to 8.5 mg N/(kg h). Investigation of the effect of environmental factors (temperature, pH, aeration, and light intensity) on potential nitrogen-fixing activity in peat samples revealed that nitrogen fixation could proceed in a wide range of pH values (from 3.0 to 7.5) and temperatures (from 5 to 35 degrees C). The nitrogen-fixing bacteria belonging to different trophic groups were enumerated by using nitrogen-free media with pH values and mineralization levels close to those in situ. In samples of peat soil, diazotrophic methanol-utilizing bacteria prevailed (2.0-2.5 x 10(6) cells/g); the second largest group was facultatively anaerobic bacteria of the family Enterobacteriaceae.

Bacteria↗