Autotrophic Research Articles

The influence of light regime on the growth data and pigment composition of the plant Gentiana lutea cultured in vitro

New technologies of reintroduction of plant species presuppose implementing both traditional and biotechnological methods for obtaining certain planting materials. However, plants cultivated in vitro exist in specific conditions that lead to changes in their structural and functional state. This explains why it is hard for them to adapt to ex vitro and in situ conditions. Therefore, there is a need for the development of a multistage method of cultivating in vitro plants that would make the influence on their adaptive mechanism in ex vitro and in situ conditions possible. One of its stages is the optimization of the light regime of cultivation which can both initiate the change of the state of the photosynthetic apparatus of plants and increase their bioproductivity stimulating the work of their protective system. This work studies changes in the morphogenesis, growth data and pigment composition of the rare species of Gentiana lutea L. of three populations in the Ukrainian Carpathian (mountains Pozhyzhevska and Sheshul-Pavlyk, plateau Lemska) in vitro focusing particularly on the cultivation light regime. The research has proved the inefficiency of using fluorescent lamps of daylight lamps (LD) type as source of illumination because the low intensity of luminous flux in the area of photosynthetically active radiation (PAR), as well as high proportion of wavelength of blue (400–500 nm) and green (500–600 nm) range in the spectrum cause specific reactions of photomorphogenesis, which, despite the high content of pigments in plastids, lead to poor development of root systems, stretching the stems, formation of small leaves with thin leaflet plate, generally low productivity and low adaptive potential of G. lutea plants to ex vitro and in situ conditions. Complement of cold white light lamps to the fluorescent lamps LD type in the ratio of 1 : 1 enables one to increase the intensity of illumination in the field of PAR and raise the fraction of wavelength of red range (600–700 nm). Such light conditions both improve the bio-productivity of G. lutea plants of all three populations cultured in vitro in comparison to the LD type regimen, reducing the content of chlorophyll b and carotenoids in light-harvesting complexes of photosystems and facilitate an increase in the microclonal multiplication factor without using higher concentrations of exogenous growth regulators,which significantly reduces the cost of the process of obtaining planting materials. It was proved that a combination of LD type lamps, cold white light lamps and phytolamps in the ratio 1 : 1 : 0.6 should be used on the final stages of preparation of the planting material of G. lutea before transferring it to ex vitro and in situ conditions. This relates to the fact that the increase of the wavelength of the red range results in the widening of the active surface of the leaves, rise in the content of photosynthetic pigments, and the noticeable growth of the aboveground and underground parts of the plants. The article assumes that the use of such illumination mode will ensure a faster transition of cultured in vitro G. lutea plants from heterotrophic to autotrophic nutrition, improving their adaptive potential and enabling easier adaptation to non-sterile ex vitro and in situ conditions.

СОВРЕМЕННЫЕ БИОПРЕПАРАТЫ И СТИМУЛЯТОРЫ РОСТА В ТЕХНОЛОГИИ ВОЗДЕЛЫВАНИЯ ПОДСОЛНЕЧНИКА НА МАСЛОСЕМЕНА

Application of biological preparations and liquid fertilizer-stimulating compositions is a perspective direction of acceleration of growth rates of production of sunflower oil raw materials in soil and climatic conditions of the middle Volga region owing to the following reasons: they stimulate the growth capacity of shoots and accelerate the transition of plants to autotrophic nutrition. As a result, a powerful deep-penetrating sunflower root system is formed, which provides additional sources of food and moisture from such deep layers of soil that are completely inaccessible to cereals; antibiotics produced by biopreparations and chelate form of copper reduces infection of seeds and crops by pathogens of basket and root rot. The number of affected plants is reduced by 35-38% depending on the varietal characteristics of the culture; a positive merger of two factors (additional nutrition and protection of plants from diseases) in one direction is the basis for the formation of highly productive agrocenoses, providing additional production of 0.26-0.27 t/ha of sunflower oil seeds (132-138 kg/ha of vegetable oil).

Can we breed for durable resistance to broomrapes

The broomrapes ( Orobanche and Phelipanche ) are parasitic plants that have modified biology to feed on other plants, completely losing autotrophic capability. Some broomrape species have adapted to agricultural ecosystems becoming parasitic weeds. The most damaging weedy broomrapes are O. crenata , O. foetida , O. minor , O. cumana , O. cernua and P. ramosa and P. aegyptiaca , which can severely constrain important dicotyledonous crops, mainly in the Mediterranean Basin. This adaptation is an active process, with recent instances of jumps from non-weedy to weedy behavior, such as for O. cumana adapting to infect sunflower little more than a century ago; O. cernua adapting to infect tomato, tobacco and eggplant; and the more recent example of O. foetida adapting to infect faba bean a few decades ago. This also relates to parasite speciation towards particular hosts, such as the ongoing process of P. ramosa populations infecting winter oilseed rape. Sunflower is a unique situation, in which highly effective monogenic resistances to broomrape have been identified and widely deployed by sunflower breeders. This was accompanied by the subsequent appearance and spread of new races of O. cumana overcoming the introduced host resistance genes. In contrast, only quantitative resistances were identified and exploited by breeders in other crops against other broomrapes. Achievements and prospects for broomrape resistance breeding are presented and critically discussed, along with complementary measures needed to preserve durability of resistance. Particularly important is the prevention of human-driven broomrape seed dispersal by crop seed trade, together with broomrape seed soil-bank demise.

Evaluation of Thiosulfate-Based Autotrophic and Mixotrophic Denitrification Performances under Different Operational Conditions

Bu calismanin amaci ototrofik ve miksotrofik denitrifikasyon proses performanslarini etkileyen faktorlerin ardisik kesikli reaktorde arastirilmasidir. Calisma verileri ototrofik denitrifikasyon prosesinin karbon icerigi dusuk atiksular icin gercek olcekte uygulanabilirligine isik tutmaktadir. Ototrofik denitrifikasyon prosesinde farkli dongu suresi, elektron vericive organik karbon ilavesinin nitrat giderim performansina etkisi sulfat, nitrat, nitrit, ORP ve inorganik karbon parametreleri ile degerlendirilmistir. Calismanin ilk asamasinda farkli dongu surelerinin (8sa-4sa-2sa) tiyosulfat (S 2 O 3 -2 ) bazli ototrofik denitrifikasyon prosesine etkisi arastirilmistir. Daha sonra 2 saatlik optimum dongu suresinde farkli S 2 O 3 -2 /NO 3 - oranlari (1,5-1,25-1) ile ototrofik denitrifikasyon prosesinin optimizasyon calismalari yurutulmustur. Elde edilen calisma bulgulari goz onunde bulunduruldugunda maksimum %84 nitrat giderim verimi 2 saatlik dongu suresi ve 1,5 S 2 O 3 -2 /NO 3 - orani ile isletilen isletim kosullarindan elde edilmistir. Calismanin son asamasinda ise farkli C/N (0,35-0,70-1,05) oranlarinin miksotrofik denitrifikasyon performansina etkisi incelenmistir ve C/N oranin 1,05 oldugu isletim kosulunda nitratin tamami tuketilirken organik madde kaynagi olarak metanolun artmasiyla nitrat giderim hizinin arttigi gozlemlenmistir.

EFFECT OF CHILLING STRESS ON THE PHOTOSYNTHETIC PERFORMANCE OF YOUNG PLANTS FROM TWO MAIZE (ZEA MAYS) HYBRIDS

: In the climate conditions of Bulgaria, early stages of maize plants development often go under suboptimal temperatures. Chilling stress is known to cause different physiological disturbances in young maize plants during the transition period from heterotrophic to autotrophic nutrition. However, the effect of chilling may differ among maize hybrids. Photosynthetic performance could be a good indicator for the hybrid tolerance to chilling. The aim of our study was to evaluate the tolerance of young maize plants from two hybrids – the new Bulgarian hybrid - Kneza 307 and the hybrid P9528 using as criteria the changes in their photosynthetic performance.Plants at the third leaf stage were exposed for seven days to chilling stress. At the end of the experimental period, growth, leaf lipid peroxidation, and several photosynthetic parameters were measured. We found that chilling stress reduced the fresh mass accumulation, increased lipid peroxidation, diminished net photosynthetic rate and chlorophyll content, and enhanced non-photochemical quenching of chlorophyll fluorescence. Although the responses of both hybrids were similar, some specificity were observed and discussed.

Dissolved organic matter uptake by Trichodesmium in the Southwest Pacific

The globally distributed diazotroph Trichodesmium contributes importantly to nitrogen inputs in the oligotrophic oceans. Sites of dissolved organic matter (DOM) accumulation could promote the mixotrophic nutrition of Trichodesmium when inorganic nutrients are scarce. Nano-scale secondary ion mass spectrometry (nanoSIMS) analyses of individual trichomes sampled in the South Pacific Ocean, showed significant 13C-enrichments after incubation with either 13C-labeled carbohydrates or amino acids. These results suggest that DOM could be directly taken up by Trichodesmium or primarily consumed by heterotrophic epibiont bacteria that ultimately transfer reduced DOM compounds to their host trichomes. Although the addition of carbohydrates or amino acids did not significantly affect bulk N2 fixation rates, N2 fixation was enhanced by amino acids in individual colonies of Trichodesmium. We discuss the ecological advantages of DOM use by Trichodesmium as an alternative to autotrophic nutrition in oligotrophic open ocean waters.

Factors affecting water availability for high Arctic lichens

Lichen symbiosis is a successful nutritional strategy that drives lichen distributions in high Arctic ecosystems. However, the in situ effects of fungal partners (mycobionts) on water availability for the photosynthetic partners (photobionts) and their necessity for survival remain unclear. We investigated the factors creating differences in water availability in high Arctic lichen assemblages using observational and experimental analyses of substrates and thallus morphology in the high Arctic, near Ny-Alesund, Svalbard (79°N) during the snow-free season. We used five lichen species found on five substrate types: moss litter, vascular plant litter, mixed litter, biological soil crust (BSC) and gravel. BSC had significantly higher water content than the other substrates; although it had high levels of surface evaporation, BSC took up more ground water. Moreover, the structure of BSC supported greater water retention than the four other substrates in our study, providing the moistest environment for lichens. In fact, 60 % of the surface area of the crustose lichen Ochrolechia frigida, which was mainly distributed on BSC, was in contact with the substrate. In contrast, the four fruticose lichens had larger surface areas than Och frig and roughly 90 % air exposure. Initial rates of absorption and evaporation increased with greater thallus surface area, suggesting that water availability for photobionts is strongly affected by both morphological characteristics and substrate water properties, both of which depend on mycobionts. We conclude that lichens show preferences for both morphologies and substrates that promote autotrophic nutrition in the water-limited glacier foreland of the high Arctic region.

The preliminary study of lipid production of Nostoc sp. from Bueng Boraphet, Nakhon Sawan Province

Our study was focused on optimum physical and nutritional conditions in lipid accumulation of microalgae (Nostoc sp.) from Bueng Boraphet using BG-11 as cultured media. Results showed that the optimum temperature and acid-base value were at 30 oC and pH 7.0, respectively under autotrophic condition. Nostoc sp. was able to properly grow and gave 0.517 g/L dry cell weight and 4.16% lipid content. The optimum nutrition for lipid accumulation by Nostoc sp. was then examined. These conditions were found to be 0.15% potassium nitrate (KNO3), 10% glucose and 0.004% dipotassium phosphate (K2HPO4) at 30 oC, pH 7.0 under mixotrophic condition. Nostoc sp. showed the highest dry cell weight and lipid content at 1.314 g/L and 4.48 percent respectively. The trend of lipid accumulation was depend on the growth rate of Nostoc sp.

Diversity of Blue Green Algae from Paddy Fields

Blue green algae are found in all types of aquatic bodies. Paddy fields represent one such habitat. An attempt has been made to isolate cyanobacteria from paddy fields of Siddipet region in Telangana State. Blue Green Algae are the most important nitrogen fixing organisms because of their autotrophic nutrition and flourish in paddy fields and known to sustain the fertility of this ecosystem. This paddy ecosystem allows BGA to function properly, selectively and effectively.To initiate the study, soil samples were collected in clean polythene bags. At the time of collection, the surface of the sampling station was cleaned by removing small stones, pebbles and grasses. The collected samples were brought to the laboratory, cultures were maintained and periodical observations were made on alga appearing in the cultures. As many as 34 species of cyanobacteria were identified.Both heterocystous and non- heterocystous forms were observed. The Nostocaceae has been reported by maximum number of genera and species. The genera Scytonema, Oscillatoria, Nostoc and Lyngbya were represented by maximum number of species.

TROPHIC CLASSIFICATION AND TEMPORAL KINETICS OF P/B, P/R, R/B AND NPP/GPP RATIOS IN THE PHOTIC LAYER OF THE DAM ZONE IN AN EQUATORIAL COLOMBIAN RESERVOIR

We studied the kinetic temporal and trophic classification of the reasons P/B, P/R, NPP/GPP and R/B in the area of ??the dam reservoir Riogrande II (6o 35’ 57’’- 6o 28’ 79’’ N; 75o 32’ 17’’-75o 25’ 85’’ O). We measured gross primary production (GPP) and net (NPP) and respiration (R) at five depths within the photic zone. Samples were taken every month between July 2002 and June 2003. Phytoplankton biomass (B) is quantified according to Sartory & Grobbellar (1984) in samples integrated within the photic zone. From the maximum values of the profiles GPP and R were established photosynthetic Coefficient (GPPmax / B), the reason GPPmax / Rmax and metabolic coefficient (Rmax / B). The ratio between the mean values ??of NPP and GPP shows that NPP was 5.2 times GPP, reflecting higher R. These considerations imply that: the biomass present structure remains due to the negentropy relatively high, and metabolically the system is more autotrophic that heterotrophic, behaving as a carbon sink. Therefore, part of the biomass is breathe not in this ecosystem. implying that there is a PPN available, functioning as a nutrient trap of type autotrophic. The metabolic coefficient ranged around the unit, confirming the relative stability of the phytoplankton assemblage, with some catabolic periods, but prioritizing the anabolic character, what effectively converts the system into a carbon sink capable of maintaining stable condition, and therefore contributions resistant entropic or anergic. Assuming that an accumulation B signifies a R increase, then P/R must be less than one. However, the ratio P/R, with an average value of 1.61 shows clearly an imbalance between the produced material and the removed or consumed by R. Considering the concentration of phytoplankton B (17.1 +11.7 MgCl. Am -3 ), the dam of the water body studied is eutrophic. The mean values ??of the coefficient of Assimilation confirm this condition.

Microalgae Biomass as an Alternative Substrate in Biogas Production

The running down of fossil energy sources makes the production of bioenergy an expected need worldwide. Therefore, energy crops have gained increasing attention in recent years as a source for the production of bioenergy because they do not compete with food crops. Microalgae have numerous advantages such as fast growth rates and not competing with food production. Because of the fast growth, many high valuable products are generated, e.g. food, biofuel, etc. Due to the energy crisis, renewable energy becomes a popular issue in this world today and there are several alternatives such as bioenergy, solar, wind, tide, geothermal, etc. For bioenergy, algae are the third generation biofuel crop. There is an increased demand for biogas in the society and one way to meet this is to use cultivated microalgae as fermentation substrate. In the present study, we maintained algae growth process and biomass production in autotrophic condition continuously for over 2 month’s period. Growth system (photobioreactor) was setup under room temperature and continuous illumination light through fluorescent lamps; light intensity was average as 48.31 [µmol-1m-2 per µA]. In reactor, dominant microalgae species were including Anabaena sp., Chlorella sp., Oscillatoria sp., Oedogonium sp. and Scenedesmus sp. The content of total solids (TS) and volatile solids (VS) in the algae biomass was measured; the results were average as 12500 g/m3 and 6320 g/m3, respectively. Furthermore, microalgal biomass is a potentially valuable fermentation substrate, and produce over 60% of methane gas.

Trophic dynamics of scleractinian corals: stable isotope evidence.

Reef-building corals form symbioses with dinoflagellates from the diverse genus Symbiodinium. This symbiotic association has developed adaptations to acquire and share nutrients, which are essential for its survival and growth in nutrient-poor tropical waters. The host is thus able to prey on a wide range of organic food sources (heterotrophic nutrition) whereas the symbionts acquire most of the inorganic nutrients (autotrophic nutrition). However, nutrient fluxes between the two partners remain unclear, especially concerning heterotrophically acquired carbon and nitrogen. We combined physiological measurements and pulse-chase isotopic labeling of heterotrophic carbon and nitrogen, as well as autotrophic carbon to track nutrient fluxes in two coral species, Stylophora pistillata and Turbinaria reniformis, in symbiosis with Symbiodinium clades A, and C,D respectively. We showed a rapid acquisition, exchange and a long-term retention of heterotrophic nutrients within the symbiosis, whereas autotrophic nutrients were rapidly used to meet immediate metabolic needs. In addition, there was a higher retention of heterotrophic nitrogen compared with carbon, in agreement with the idea that tropical corals are nitrogen-limited. Finally, a coupling between auto- and heterotrophy was observed in the species S. pistillata, with a higher acquisition and retention of heterotrophic nutrients under low irradiance to compensate for a 50% reduction in autotrophic nutrient acquisition and translocation. Conversely, T. reniformis conserved an equivalent heterotrophic nutrient acquisition at both light levels because this coral species did not significantly reduce its rates of gross photosynthesis and autotrophic carbon acquisition between the two irradiances. These experiments advance the current understanding of the nutrient exchanges between the two partners of a symbiotic association, providing evidence of the complexity of the host-symbiont relationship.

Effect of bacteria biomass detachment on the ammonium oxidation yield

Nitrification yield can be affected by fixed biomass or biofilm density. Infact, biofilm detachment may influence the nitrification. The present experiment investigated the effect of detachment biomass cells on nitrifying bacteria expressed via nitrification rate. We monitored nitrification rates before and after biomass detachment from gravel sampled in a small-scale model of wastewater treatment using macrophytes in vertical and horizontal filtersystems. The ammonia-oxidizing bacteria (AOB) number decreased after cell detachment whereas the number of nitrite-oxidizing bacteria (NOB) was lower and saving a constant value of 3.0 MPN/100 ml. Despite this detachment, the yield of ammonium oxidation in the vertical filter remains constant but the reaction required more time. After washing, the NO3--N concentration at the bottom of horizontal filter with fine gravel is more important (1.24 mg/l) than that observed at the medium (1.1 mg/l) and the top (0.8 mg/l) of basin; whereas, at the horizontal filter with coarse gravel, the nitrification performance is more important at the medium of basin with NO3--N concentration value of 1.14 mg/l than those obtained at the top (0.7 mg/l) and the bottom (0.98 mg/l). Key words: Autotrophic bacteria, detachment, nitrification, turbidity.

Exoelectrogenic activity of a green microalgae, chlorella vulgaris, in a bio-photovoltaic cells (bpvs)

Bio-photovoltaic cells (BPVs) are a new photo-bio-electrochemical technology for harnessing solar energy using the photosynthetic activity of autotrophic organisms. This is a new technology for the production of sustainable and “clean” energy.Currently power outputs from BPVs are generally low and suffer from scarce efficiencies. However, a better understanding of the electrochemical interactions between the autotrophic microorganisms and conductive materials will be likely to lead to increased power yields. In the current study, the green microalgae Chlorella vulgaris was investigated for exoelectrogenic activity.To assess the exoelectrogenic activity of C. vulgaris a particular bio-photovoltaic cell was designed and built. The most important element is represented by the electrode configuration, based on inexpensive materials, with the anode immersed in the cultural broth and the cathode exposed to the atmosphere. This configuration represents a very interesting simplification for the cell design, furthermore allowing a simple illumination of the algal culture via a light source positioned above the cell, perpendicular to the electrode surface.This new kind of bioelectrochemical system does not need organic substrate and mediators, and the net production of CO2 is zero.This device was then characterized by measuring the electrical performance of the BPV. A power density of 14 µW/m2 was recorded, revealing interesting potentialities for green unicellular algae fuelled BPVs.

Cultivation of microalga, Chlorella vulgaris under different auto–hetero–mixo trophic growths as a raw material during biodiesel production and cost evaluation

The biomass and lipid productivities of green microalga, Chlorella vulgaris TISTR 8580 cultivated in the Bold's basal medium under three different culture conditions namely AC (autotrophic), HC (heterotrophic) and MC (mixotrophic) cultivations in a 20 L rectangular bioreactor were investigated. Maximum cell growths were obtained on day 10, 3 and 5 under AC, HC and MC, respectively. The C. vulgaris cells in heterotrophic condition contained the highest amount of lipids (32.9%) and the lowest amount of proteins (14.5%). The composition of C. vulgaris cells under MC condition was found to be between those found at AC and HC conditions. The most efficient energy production system in terms of lipid production to energy consumption was MC. The biodiesel yield was about 93.3% and fatty acid in methyl esters were found as 35.33% palmitic acid, 19.01% oleic acid, 19.21% linoleic acid, 11.68% linolenic acid and 14.77% others.

A phylogenetic approach to the early evolution of autotrophy: the case of the reverse TCA and the reductive acetyl-CoA pathways.

In recent decades, a number of hypotheses on the autotrophic origin of life have been presented. These proposals invoke the emergence of reaction networks leading from CO or CO₂ to the organic molecules required for life. It has also been suggested that the last (universal) common ancestor (LCA or LUCA) of all extant cell lineages was a chemolitho-autotrophic thermophilic anaerobe. The antiquity of some carbon fixation pathways, the phylogenetic basal distribution of some autotrophic organisms, and the catalytic properties of iron-sulfur minerals have been advanced in support of these ideas. Here we critically examine the phylogenetic distribution and evolution of enzymes that are essential for two of the most ancient autotrophic means of metabolism: the reductive tricarboxylic acid (rTCA) cycle and the reductive acetyl-CoA pathway. Phylogenetic analysis of citryl-CoA synthetase and of citryl-CoA lyase, key enzymatic components of the rTCA cycle, and of CO dehydrogenase/acetyl-CoA synthase, a key enzyme in the reductive acetyl-CoA pathway, revealed that all three enzymes have undergone major lateral transfer events and therefore cannot be used as proof of the LCA's metabolic abilities nor as evidence of an autotrophic origin of life.

AN ASSESSMENT OF NUTRIENT BIOGEOCHEMICAL CYCLES IN THE INNER GULF OF THAILAND

The nutrient dynamics of the Inner Gulf of Thailand were studied using a simple steady-state budget model, according to the Land–Ocean Interaction in the Coastal Zone modelling guidelines. Two sampling campaigns were carried out during the wet (October 2011) and the dry (February 2012) seasons. For each season, budgets for water and salinity, dissolved inorganic phosphate (DIP) and nitrogen (DIN) were determined. The study indicates that the Inner Gulf exports water at the rate of 133-562 MCM.day -1 in the form of residual flux (V R ) at the inner-outer Gulf interface. This results in export of salt to the inner-outer Gulf interface at the rate of 4.3x10 3 –17x10 3 ton.d -1 . Exchange between the Inner Gulf water and the adjoining seawater replaces this salt loss. Mass balance calculations indicate that the Inner Gulf is a net source for DIP and DIN to the adjacent outer Gulf water at the rate of 4.0x10 4 -3.4x10 6 molP.d -1 and 4.1x10 6 - 20.5x10 6 molN.d -1 , during the dry and wet season respectively. The high DIP and DIN exports during the wet season probably reflect the inputs coming from the agricultural, domestic and industrial wastes during the severe flooding over Thailand in 2011. Stoichiometric analysis yields the values of net ecosystem metabolisms (NEM; p-r) and net nitrogen production (nfix-denit) in the Inner Gulf at the rate of 4.4x10 3 tons C.d -1 and 0.7x10 3 tons N.d -1 , indicating that the Inner Gulf is an autotrophic (sink of nutrients) and net nitrogen fixing (nfix-denit >0) ecosystem during the wet season. However in the dry season, the Inner Gulf remains to be autotrophic (p-r = 47 tonsC.d -1 ) but shifted to be a net denitrifying ecosystem (nfix-denit = -88 tonsN.d -1 ). Results from the nitrogen and phosphorus biogeochemical cycling revealed the importance of river discharges in the transport and transformation of these substances within the Inner Gulf of Thailand.

Azo dye remediation in periodic discontinuous batch mode operation: Evaluation of metabolic shifts of the biocatalyst under aerobic, anaerobic and anoxic conditions

Shifts in microbial metabolism with the function of aerobic, anaerobic and anoxic microenvironments were evaluated in periodic discontinuous batch mode operation in response to the treatment of azo dye (C.I.Acid Black 10B) bearing wastewater. Anoxic operation depicted higher dye removal efficiency (95.18%) followed by anaerobic (93.67%) and aerobic (68.77%) operations. Switching between aerobic and anaerobic metabolic functions during anoxic operation facilitated the reduction of dye to its intermediates (anaerobic) followed by their mineralization (aerobic). Function of dye as a terminal electron acceptor (TEA) along with the limited oxygen available might be the reason for the observed higher dye removal under anoxic operation. Azo reductase activity showed marginal variation with the function of anoxic and anaerobic conditions indicating the similar capabilities of the biocatalyst. However, dehydrogenase activity showed significant variation with the function of operating microenvironment indicating the differences in the delivery of reducing powers from the substrate metabolism towards dye removal. The bio-electro kinetics showed well correlation with the redox reactions, enzyme activities and dye removal. Microbial inventory analysis documented the involvement of organisms with anaerobic and facultative metabolic functions having heterotrophic and autotrophic nutrition modes. Aerobic operation documented the dominance of facultative (83%) followed by obligative aerobic (17%) bacteria while anoxic and anaerobic operations facilitated the distribution of facultative (67% and 83%, respectively) and obligative anaerobic (33% and 17%, respectively) bacteria.

The role of promoter methylation in the regulation of genes encoding succinate dehydrogenase in maize seedlings

The activity of succinate dehydrogenase (SDH) changed during maize (Zea mays L.) seed germination. On the fifth day of germination, the activity was the highest, which might be evidently explained by accelerated utilization of stored carbohydrates and lipids. Subsequent decrease in SDH activity might be related to metabolism switching to autotrophic nutrition. The correlation was found between the levels of sdh1-1 and sdh1-2 gene transcription and the extent of methylation of their promoters. During seed germination, promoter methylation of genes encoding the subunit A of SDH was activated, which resulted in suppression of their transcription. It is suggested that this mechanism may play an important role in the regulation of sdh1-1 and sdh1-2 gene transcription in plant tissues.

Culturable autotrophic ammonia-oxidizing bacteria population and nitrification potential in a sheep grazing intensity gradient in a grassland on the Loess Plateau of Northwest China

Liu, T., Nan, Z. and Hou, F. 2011. Culturable autotrophic ammonia-oxidizing bacteria population and nitrification potential in a sheep grazing intensity gradient in a grassland on the Loess Plateau of Northwest China. Can. J. Soil Sci. 91: 925-934. Grazing is known to enhance the activity of soil microbial communities in many types of grasslands; however, the potential impacts of rotational grazing activity on soil microbial functional groups remain poorly understood. We investigated the effects of 9 yr of rotational grazing by livestock on culturable autotrophic ammonia-oxidizing bacteria (AOB) population size, nitrification potential and soil properties in a semi-arid grassland of the Loess Plateau in Northwest China. Three stocking rate treatments of 2.7, 5.3 and 8.7 wether lambs ha-1 were evaluated in geographically separated paddocks. Grazing increased nitrification potential and culturable AOB populations compared with ungrazed treatments. Ammonia-oxidizing bacteria populations increased from 155 bacteria g-1 dry soil with 0 sheep ha-1 to 16 218 bacteria g-1 dry soil with 8.7 sheep ha-1. Grazing led to an increase in population of AOB at 0-10 cm soil depth, but had no effect on AOB at 10-20 cm soil depth. Nitrification potential increased from 1.21 mg NO3-N kg-1 soil d-1 in ungrazed treatments to 2.86 mg NO3-N kg-1 soil d-1 at the highest stocking rate. Soil ammonium and nitrate concentrations increased; however, total soil nitrogen and soil moisture content decreased with increased stocking rate for both sampling depths (0-10 cm and 10-20 cm). Soil organic matter was not affected by grazing treatments. Soil nitrification potential and the size of culturable AOB populations were dependent on grazing intensity, soil depth and season. This information is potentially important for the optimal selection of stocking rate for grazed ecosystems.