Average Transformation Rate Research Articles

Nitrogen Removal Mechanism and Microbial Community Changes of the MBR Bioaugmented with Two Novel Fungi Pichia kudriavzevii N7 and Candida tropicalis N9

Ammonia nitrogen wastewater causes dissolved oxygen concentrations to decrease and the content of harmful substances to increase. To characterize the application properties of two novel strains of highly efficient ammonium transforming fungi—Pichia kudriavzevii N7 and Candida tropicalis N9—this study used both as compound microbial agents to treat nitrogenous wastewater. Here, we investigated the bioaugmentation effect of compound fungi N7 and N9 in the MBR bioreactor and the effect of N7 and N9 on the fungal and bacterial microbial communities in the system. The results revealed that in the first week after inoculation of N7 and N9, the average removal rate of ammonium in the experimental and control groups were 89.43% and 82.86%, respectively, and the NO3−-N accumulation concentrations were 12.56 mg·L−1 and 17.73 mg·L−1, respectively. The average transformation rate of total nitrogen in the experimental and control groups were 46.32% and 30.6%, respectively. ITS sequencing results indicated that N9 could be a dominant fungus in the complex MBR system. The results of 16S rRNA sequencing showed that the dominant bacterial communities in the system were changed by the inoculation of compound fungi. Therefore, the compound fungi can be applied to strengthen the treatment of nitrogenous wastewater due to its compatibility.

Compartmentalization transformation of Fe2+, Mn2+ and NH4+ in groundwater: A comparative research containing experimental medium and functional genera profiling derived from experiment data

Contamination of soluble iron (Fe2+), manganese (Mn2+), and ammonium (NH4+) in groundwater is prevalent, particularly in Northeast China. This study aims to elucidate the intricate biological and physical-chemical reactions involved in the sequential transformation of three target contaminants. Two dynamic column simulations were used to compare quartz sand filtration (QSF) system with riverbank filtration (RBF) system to assess the interactions and respective contributions of the reactions involved in transforming process. Similar pattern of transformation vertical compartmentalization in two systems along the filter depth were founded, and the Fe2+ transformation was mainly distributed in the upper part, while NH4+ and Mn2+ occurred primarily in the downstream sections. The average transformation rate of Fe2+, Mn2+ and NH4+ in RBF system was 84.52 %, 47.68 % and 67.95 %, respectively, which was 5.20 %, 11.43 % and 23.06 % higher than in QSF system. The dominant transformation process for Fe2+ in RBF involved chemical oxidation, bio-oxidation and adsorption. The lower transformation rate for Mn2+ was attributed to abiotic homogenous oxidation limitation and negative affect derived from high concentration of NH4+ with high nitrification rate in RBF system. Nitrification by Nitrosomonas and Nitrospira was critical NH4+ transformation mechanism in RBF system, while the adsorption by iron and manganese oxide and aerobic denitrification were contributed strongly to NH4+ transformation in QSF system. Furthermore, the spatial distribution of functional bacterial genera was in good consistent with the transformation compartmentalization of three target contaminants in both systems, and similar microbial community structure reflected the domestication effect of groundwater chemistry on functional bacteria.

THE EVOLUTION OF DIGITAL TRANSFORMATION IN SMES IN THE MANUFACTURING INDUSTRY IN THE DIFFERENT BLOCKS OF THE BM CANVAS SINCE THE BEGINNING OF THE PANDEMIC

Purpose – The following article focuses on assessment of the evolution of digital transformation in SMEs in the manufacturing industry since the beginning of the pandemic. The digital transformation is assessed in the different blocks of the BM Canvas. The main objective of the paper is to evaluate the impact of the pandemic on the development of digital transformation, and to assess whether it is still influencing it now, or vice versa, or no longer has such an impact. Research methodology – The digital transformation is examined in each block of the Business Model Canvas (BM Canvas) from the beginning of the pandemic to the current state. The individual data is obtained from a survey conducted among 18 SMEs. Small and medium-sized enterprises in the manufacturing industry are examined. The survey is based on semi-structured interviews with SME´s management representatives. The collected data is then processed by examining the average rate of digital transformation in each block, the modus, and the median. The focus was again on developments and changes in the digital transformation of enterprises. The data was collected for three periods – before the pandemic (2019), during the pandemic (2021) and now (July 2022). Findings – The paper shows the evolution of digital transformation in the different building blocks of the BM Canvas for SMEs in the manufacturing industry since the beginning of the pandemic. The evolution of digital transformation varies across the BM Canvas blocks. For the Channels block, as of July 2022, there has been a decrease in the average digital transformation rate. The other blocks have seen an increase and continue to develop. However, the increases are no longer as high as in 2021. Whether digital transformation will continue to develop for individual blocks in future periods is a suitable research question for further research. The findings show that the changes and developments vary from building block to building block. It was found that the importance of each building block changed during the pandemic for each firm representative. The results provide the basis for the analysis of the development and change of BM Canvas for individual companies. Research limitations – At the moment, the current situation in Ukraine, in addition to the COVID-19 pandemic, is playing a major role in SMEs activities as it affects companies. This conflict was not considered in the research, and the development since the beginning of the pandemic was followed. Practical implications – This research highlights how the digital transformation of individual SMEs in the manufacturing industry is evolving. It highlights the impact of the pandemic, which has undoubtedly increased the growth of digital transformation rates. For future research, these results can be very useful, as other influences on the rates of digital transformation can be investigated. Originality/Value – The research was carried out on the basis of primary data collected by the authors themselves. The data were processed and evaluated. The results of the research show how the level of digital transformation in different blocks of the BM Canvas has evolved from the beginning for each SME in the manufacturing industry.

Experimental Investigation on the Inhomogeneities of Transverse Microstructure and Internal Stress of High‐Strength Low‐Alloy Hot‐Rolled Strip

Herein, the evolution of transformation in the width direction of high‐strength low‐alloy hot‐rolled strip is studied by using thermomechanical simulation, and the temperature, microstructure, and internal stress are correlated based on electron backscatter diffraction data. The temperature and time range of the transverse transformation are determined based on the thermal expansion curve. The results show that the transformation at the edge of the steel plate ends earliest and that at the plate center begins at the latest; only 31.9% austenite undergoes transformation at the plate central by the end of laminar cooling. The fraction of transformed austenite at the plate center is the least throughout the laminar cooling process. The proportion of small grains (within the grain size range of 0–4 μm), mean, and variant coefficient of grain sizes at the plate edge are 75%, 4 μm, and 1.29, respectively. In contrast, those values of the central region are 66%, 4.4 μm, and 1.05, respectively. The correlation between temperature and internal stress evolutions is established. It is demonstrated that the internal stress increases monotonically with the average transformation rate.

Response of 2,4,6-trichlorophenol-reducing biocathode to burial depth in constructed wetland sediments

Biocathode systems could be used for in-situ bioremediation of chlorophenols (CPs) in constructed wetland (CW) sediments. However, little is known regarding whether or how cathode burial depths affect the dechlorination of CPs in sediments. Here, 2,4,6-trichlorophenol (2,4,6-TCP)-dechlorinating biocathode systems were constructed under a cathode potential of − 0.7 V (vs. a saturated calomel electrode, SCE) at three different cathode burial depths (5, 10, and 15 cm). The 2,4,6-TCP removal efficiency and average transformation rate with the biocathode increased by 21.46–36.86% and 14.63–34.88% compared to those in the non-electrode groups. Deeper cathode burial depths enhanced the 2,4,6-TCP dechlorination performance. Furthermore, the oxidation-reduction potential (ORP) of the sediment decreased with sediment depth and the applied potential created a more favorable redox environment for the enrichment of functional bacteria. Deeper cathode burial depths also promoted the selective enrichment of electro-active and dechlorinating bacteria (e.g., Bacillus and Dehalobacter, respectively). The biocathode thus served as the carrier, electron source, and regulator of functional bacteria to accelerate the transformation of 2,4,6-TCP (2,4,6-TCP → 2,4-dichlorophenol → 4-chlorophenol → phenol) in sediments. These results offer insights into the effects of cathode burial depth on 2,4,6-TCP dechlorination in sediments from a redox environment and microbial community structure standpoint.

(Invited) Probing Heterogeneous Transformations in NMC Cathodes with Microbeam Diffraction

Ideally, the redox activity in Li-ion batteries, which is associated with storage and release of Li ions, is distributed homogeneously throughout the electrode, thereby minimizing detrimental processes while maximizing battery performance. However, it appears that every electrode material displays inhomogeneous redox activity which is expected to play a dominant role in battery performance parameters such as cycle life, efficiency and rate performance.1 For example, the occurrence of localized redox activity in layered electrodes can accelerate degradation reactions through local strain and/or decomposition1-2. Further, inhomogeneous reactions render estimating the true state of charge challenging and can introduce history effects3 that make optimization of battery performance via a battery management system problematic. Inhomogeneous redox reactions in Li-ion battery electrodes can occur on different length scales, starting at the nm length in individual electrode particles progressing up to the dimensions of complete composite electrodes (tens of μm) and can have various origins. Most directly, inhomogeneous reactions in electrodes stem from charge transport limitations, generally determined by the electrode morphology (including electrode thickness, porosity and tortuosity).4-6 A second origin for inhomogeneous reactions can be a difference in insertion potential, through mixing electrode materials5 or due to a distribution of nanoparticle sizes.7 Lastly, the nature of the phase transition can also give rise to inhomogeneous reactions. For example, the particle-by-particle transformation mechanism in LiFePO4 has been associated with a hysteresis effect8 and has been suggested to give rise to a memory effect that can influence the observed potential.3 Despite the above, limited research has been performed on this subject to date and many questions remain, mainly due to the difficulty to probe these heterogeneities in realistic battery geometries and during cycling conditions.Here we present a study of the phase transformation of ten's of individual NMC crystallites under operando cycling conditions in pouch cells using microbeam diffraction (ID11, ESRF, France). Due to the small, bright and sub-micron sized synchrotron beam diffraction rings observed with powder diffraction fall apart in individual spots each representing individual NMC crystallites in the positive electrode. In this way the phase transition behaviour through time of ten's of individual NMC crystallites is monitored at the same time while varying the electrochemical conditions.9,10 Figure 1 shows snapshots of the (108) and (110) reflection of individual NMC111 crystallites during a full C/4 charge-discharge cycle, demonstrated the anticipated continuous shift. For each individual crystallite the evolution of the lattice parameters provide insight in the distribution of the composition and local potential of each crystallite, as well as the individual transformation rate. In addition the average transformation rate can be translated in the active particle fraction and average local current density. By studying this for the series NMC111, NMC622 and NMC811, we gain insight in the heterogeneous redox activity and the impact of composition, relevant for both rate performance and cycle life of this class of intercalation cathodes. Figure 1. Following the phase transformation of single NCM111 crystallites through the (108) and (110) reflection during C/4 charge and discharge. Zhang et al. Journal of Materials Chemistry A 2019, 7 (41), 23628-23661. Lin et al. Nature Communications 2014, 5 (1), 3529. Sasaki et al. Nature Materials 2013, 12 (6), 569-575. Strobridge et al. Chemistry of Materials 2015, 27 (7), 2374-2386. Sasaki et al. Advanced Science 2015, 2 (7), 1500083. Zhang et al. Advanced Energy Materials 2015, 15, 1500498. Van der Ven et al. Electrochemistry Communications 2009, 11 (4), 881-884. Dreyer et al. Nature Materials 2010, 9 (5), 448-453.van Hulzen et al. Font. Energy Res. 2018, 6 (59). 5.Zhang et al. Nature Commun. 2015, 6 Figure 1

Whole-cell biosynthesis of 2-O-α-D-glu-copyranosyl-sn-glycerol by recombinant Bacillus subtilis

2-O-α-D-glu-copyranosyl-sn-glycerol is a high value-added product with prospective application in food, cosmetics, health products and pharmaceutical industries. However, industrial scale of 2-O-α-D-glu-copyranosyl-sn-glycerol has not yet been applied in China, and there are few related reports on 2-O-α-D-glu-copyranosyl-sn-glycerol synthesis. The purpose of this experiment is to develop a method for catalyzing the synthesis of food-grade 2-O-α-D-glu-copyranosyl-sn-glycerol using whole cells of "Generally Recognized as Safe" (GRAS) recombinant Bacillus subtilis. In our work, a recombinant B. subtilis 168/pMA5-gtfA that heterologously expressing Leuconostoc mesenteroides sucrose phosphorylase was constructed and used as a whole-cell catalyst to synthesize 2-O-α-D-glu-copyranosyl-sn-glycerol. Optimizing the culture temperature, time and whole cell transformation conditions has increased the yield of 2-O-α-D-glu-copyranosyl-sn-glycerol. The results showed that 1.43 U/mL of sucrose phosphorylase was achieved in B. subtilis 168/pMA5-gtfA after culturing for 20 h at 30 °C in fermentation medium. The highest conversion rate reached 75.1%, and the yield of 2-O-α-D-glu-copyranosyl-sn-glycerol was 189.3 g/L with an average transformation rate of 15.6 mmol/(L·h) after 48 hours whole-cell transformation with the sucrose concentration of 1 mol/L and the glycerol concentration of 2.5 mol/L at 30 °C, OD₆₀₀ 40 and pH 7.0. This is the highest yield of 2-O-α-D-glu-copyranosyl-sn-glycerol synthesized catalytically by recombinant B. subtilis that was ever reported, and this study provides the theoretical and experimental basis for the industrial production and application of 2-O-α-D-glucopyranosyl-sn-glycerol.

Characterization of an algal phosphomannose isomerase gene and its application as a selectable marker for genetic manipulation of tomato

Establishing a transgenic plant largely relies on a selectable marker gene that can confer antibiotic or herbicide resistance to plant cells. The existence of such selectable marker genes in genetically modified foods has long been criticized. Plant cells generally exhibit too low an activity of phosphomannose isomerase (PMI) to grow with mannose as a sole carbon source. In this study, we characterized PMI from the green microalga Chlorococcum sp. and assessed its feasibility as a selectable marker for plant biotechnology. Chlorococcum sp. PMI (ChlPMI) was shown to be closely related to higher plants but more distant to bacterial counterparts. Overexpression of ChlPMI in tomato induced callus and shoot formation in media containing mannose (6 g/L) and had an average transformation rate of 3.9%. Based on this transformation system, a polycistronic gene cluster containing crtB, HpBHY, CrBKT and SlLCYB (BBBB) was co-expressed in a different tomato cultivar. Six putative transformants were achieved with a transformation rate of 1.4%, which produced significant amounts of astaxanthin due to the expression of the BBBB genes. Taken together, these findings indicate that we have established an additional tool for plant biotechnology that may be suitable for genetically modifying foods safely.

Isochronal and isothermal phase transformation in β + αacicular Ti–55531

Duplex aging is one of the common heat treatments in titanium alloys. The microstructure introduced in the first-step aging has an effect on the growth/dissolution of α in the second-step aging. In the present work, a β + αacicular microstructure is preset in Ti–55531 (Ti-5Al-5Mo-5V-3Cr-1Zr wt%) alloy. The isochronal and isothermal phase transformation kinetics in the second-step aging is studied by combining the dilatometer test with microstructure characterization and local composition mapping. The phase transformations and corresponding temperature ranges are determined as β → αacicular [643–845 K] and αacicular → β [845–1130 K] by isochronal annealing. A TTT diagram for isothermal transformation kinetics is plotted based on the transformed phase fraction and reproduced by Johnson–Mehl–Avrami theory. The calculated kinetic curves are in good agreement with experiment ones. The C-shaped TTT curves verify the classical nucleation and growth of α in the second-step aging. In comparison with Ti–55531 alloy with preset β + αlath microstructure (in authors’ previous work), the α precipitation exhibits prolonged incubation period and slowed average transformation rate, which is evidenced by a right shift of C-curves for the α precipitation portion along the time axis. However, the C-curves of α dissolution show a left shift on the TTT diagram. The precipitation kinetics of α aciculae from dilatometry is synchronous with that obtained from the diffusion of Al detected in STEM mapping, while the diffusion of slow-diffusion elements lags behind the structural transformation. The TTT diagram and the dataset of microstructure features obtained in the present work can be employed to optimize processing in duplex aging.

Process study of biogeochemical cycling of dissolved inorganic arsenic during spring phytoplankton bloom, southern Yellow Sea

Previous studies in the southern Yellow Sea (SYS) suggest that large spring phytoplankton blooms (SPBs) have occurred in recent decades. Elevated primary production in the water column can lead to the accumulation and transformation of trace elements. Two field study cruises (including two drifting anchor surveys) were conducted on 12–19 February and from 24 March to 15 April 2009, to investigate the impact of different SPB development periods on the concentrations of total dissolved inorganic arsenic (TDIAs: [TDIAs]=[As(V)]+[As(III)]) and As(III) (arsenite) in the SYS. The distribution of TDIAs in the study area was similar between the two field studies, with concentrations increasing from coastal to offshore areas. High arsenite concentrations and As(III)/TDIAs ratios were found in areas having high concentrations of chlorophyll-a, particularly in the subsurface waters of the central SYS during the drifting surveys, where a significant SPB occurred. Results show that the integrated arsenite concentrations increased at an average transformation rate of 0.53±0.24nmol/L/d within the 15days during the bloom, and data from the anchor drifting surveys indicated that approximately 15.1% of the arsenate in the euphotic zone (~30m depth) was converted to arsenite. In addition, 7.1% of TDIAs was scavenged from the water column by phytoplankton forming the blooms (a factor of 5 higher than expected). A preliminary box model was established to estimate the budget for TDIAs in the SYS in early spring (February to April). This showed that biological scavenging is an important sink for TDIAs, which may promote the transformation and migration of inorganic arsenic species, and thus have a substantial impact on the biogeochemical cycling of this element in the SYS. Depletion of arsenate in the upper waters could lead to arsenate stress, potentially damaging fisheries and the ecosystem.

Spatial Variability of Anaerobic Processes and Wastewater pH in Force Mains.

The present study focuses on anaerobic organic matter transformation processes in force mains for the purpose of improving existing sewer process models. Wastewater samples were obtained at 100 m intervals from a 1 km long pilot scale force main and measured for several wastewater parameters. Transformation rates for selected parameters were calculated and their spatial variability analyzed. In terms of electron transfer, fermentation was the most significant process, resulting in a net volatile fatty acid formation of 0.83 mmol/L. Sulfate reduction resulted in a production of 0.73 mmol/L of inorganic sulfide. Methanogenesis was negligable in all experiments despite an anaerobic residence time of more than 30 hours. As a result of the anaerobic processes, the wastewater pH decreased by approximately one pH unit, resulting in a corresponding increase in the fraction of molecular hydrogen sulfide. A significant spatial variablilty was observed for the average transformation rates of all parameters.

Reflective metamaterial polarization converter in a broad frequency range

We propose a broadband reflective metamaterial polarization converter which is composed of arrays of split-ring resonators (SRRs), a dielectric layer and a continuous metallic layer. For the case of a loss-free dielectric layer, the average transformation rate is around 90% at frequencies from 6.68 to 10.91 GHz, and the bandwidth is 56.66% of the central wavelength. The increased loss tangent of the dielectric layer is shown to induce a reduced transformation rate due to enhanced absorption.

Agrobacterium-mediated genetic transformation and regeneration of transgenic plants using leaf midribs as explants in ramie [Boehmeria nivea (L.) Gaud

In this study, leaf midribs, the elite explants, were used for the first time to develop an efficient regeneration and transformation protocol for ramie [Boehmeria nivea (L.) Gaud.] via Agrobacterium-mediated genetic transformation. Sensitivity of leaf midribs regeneration to kanamycin was evaluated, which showed that 40 mg l(-1) was the optimal concentration needed to create the necessary selection pressure. Factors affecting the ramie transformation efficiency were evaluated, including leaf age, Agrobacterium concentration, length of infection time for the Agrobacterium solution, acetosyringone concentration in the co-cultivation medium, and the co-cultivation period. The midrib explants from 40-day-old in vitro shoots, an Agrobacterium concentration at OD600 of 0.6, 10-min immersion in the bacteria solution, an acetosyringone concentration of 50 mg l(-1) in the co-cultivation medium and a 3-day co-cultivation period produced the highest efficiencies of regeneration and transformation. In this study, the average transformation rate was 23.25%. Polymerase chain reactions using GUS and NPTII gene-specific primers, Southern blot and histochemical GUS staining analyses further confirmed that the transgene was integrated into the ramie genome and expressed in the transgenic ramie. The establishment of this system of Agrobacterium-mediated genetic transformation and regeneration of transgenic plants will be used not only to introduce genes of interest into the ramie genome for the purpose of trait improvement, but also as a common means of testing gene function by enhancing or inhibiting the expression of target genes.

Conditions of Retinal Glial and Inflammatory Cell Activation after Irradiation in a GFP-Chimeric Mouse Model

Microglia cells have been associated with immunologic defense and repair. The course of retinal disease after lethal irradiation for bone marrow depletion and substitution was evaluated with respect to macrophage and microglial involvement. Lethal irradiation in C57BL/6 mice was conducted with a low-voltage radiation unit. The animals were randomized to shielded or unshielded radiation and subsequently received transplants of GFP+ bone marrow cells (beta-actin promoter). The GFP transformation rate was analyzed by flow cytometry. GFP+ cells in the retina were examined for co-localization with macrophage and dendritic cell markers at various time points between 1 and 7 months after irradiation. Clodronate liposomes were used to investigate the fate of migrated and residential microglia cells. Pathologic angiogenesis was investigated in laser-induced choroidal neovascularization (CNV) after unshielded and shielded irradiation. Flow cytometry revealed average transformation rates of 78.2% in unshielded and 64.1% in shielded group. Four weeks after transplantation, perfused flat mounts were virtually free of extravasal GFP+ cells in both groups, whereas 4 months after irradiation, cluster cell infiltrations, preferentially in the peripheral retina, became apparent exclusively in the unshielded group. Cell morphology ranged from oval, to a few extensions, to dendritiform with long-branched extensions. Clodronate treatment resulted in a reduction of GFP+ cells in the retinal tissue when applied 3 months after unshielded irradiation. Although GFP+ cells accumulated in the choroidal scar after laser treatment, in both the shielded and unshielded groups, GFP+ cells in the overlying retina were restricted to the unshielded group. Approximately 3 months after lethal full-body irradiation including the eye, bone marrow-derived leukocytes exhibit a wound-healing reaction, and unlike physiological turnover, infiltrate the retina and form microglial cells.

Transgenic ramie [Boehmeria nivea (L.) Gaud.]: factors affecting the efficiency of Agrobacterium tumefaciens-mediated transformation and regeneration

In the present study, an efficient Agrobacterium-mediated gene transformation system was developed for ramie [Boehmeria nivea (L.) Gaud.] based on the examinations of several factors affecting plant transformation efficiency. The effects of Agrobacterium cell density, acetosyringone, co-cultivation temperature, co-cultivation duration, co-cultivation photoperiod and pH on stable transformation were evaluated. Agrobacterium at a concentration of OD = 0.5-0.8 improved the efficiency of transformation. Concentration of acetosyringone at 50 mg/L during co-cultivation significantly increased transformation efficiency. Co-cultivation at 20 degrees C, in comparison to 15, 25 and 28 degrees C, consistently resulted in higher transformation frequencies. A relatively short co-cultivation duration (3 days) was optimal for ramie transformation. Co-cultivation medium at pH 5.9 and co-cultivation in darkness both improved the transformation efficiencies of ramie. An overall scheme for producing transgenic ramie is presented, through which an average transformation rate from 10.5 to 24.7% in five ramie varieties was obtained. Stable expression and integration of the transgenes were confirmed by histochemical GUS assay, kanamycin painting assay, PCR and Southern blotting. This optimized transformation system should be employed for efficient Agrobacterium-mediated transformation of ramie.

Production of recombinant single chain antibodies (scFv) in vegetatively reproductive Kalanchoe pinnata by in planta transformation

We developed an asexual reproductive plant, Kalanchoe pinnata, as a new bioreactor for plant-based molecular farming using a newly developed transformation method. Leaf crenate margins were pin-pricked to infect the plant with the Agrobacterium strain LBA4404 and vacuum infiltration was also applied to introduce the target gene into the plants. Subsequently, the young mother leaf produced new clones at the leaf crenate margins without the need for time- and labor-consuming tissue culture procedures. The average transformation rates were approximately 77 and 84% for pin-prickling and vacuum-infiltration methods, respectively. To functionally characterize an introduced target protein, a nucleic acid hydrolyzing recombinant 3D8 scFv was selected and the plant based 3D8 scFv proteins were purified and analyzed. Based on abzyme analysis, the purified protein expressed with this system had catalytic activity and exhibited all of properties of the protein produced in an E. coli system. This result suggested that vegetatively reproductive K. pinnata can be a novel and potent bioreactor for bio-pharmaceutical proteins.

AGROBACTERIUM-MEDIATED TRANSFORMATION OF OLIVE (OLEA EUROPAEA L.) EMBRYOGENIC CULTURES

Olive (Olea europaea L.) breeding programs are hampered by the long juvenile period shown by this species. Genetic transformation would allow incorporation of interesting agronomical traits in much shorter times. Our group has developed an Agrobacterium-mediated transformation protocol for this species using embryogenic cultures as explants. In this protocol, somatic embryos derived from radicle explants are co-cultured with A. tumefaciens strain AGL1 containing the binary vector pBINUbiGUSint with the nptII gene for kanamycin selection and uidA gene as reporter. After 12 weeks of selection in the presence of 200 mg/L paromomycin, an average transformation rate of 17.5±5.2 was obtained, based on the number of infected explants proliferating in the selection medium. Almost 32% of the paramomycin resistant calli showed GUS activity. Somatic embryos from different transgenic lines were maturated and germinated under a constant selection pressure of 200 mg/L paramomycin, and the shoots obtained proliferated in DKW medium. Putative transgenic shoots were challenged to proliferate in the presence of increasing concentrations of paramomycin. Control shoots did not grow at low antibiotic concentration (25 mg/L). However, transgenic shoots showed good proliferation rates at 25 and 50 mg/L paramomycin, and shoot length was only reduced to 62% compared to the length of control shoots at 100 mg/L paramomycin. Transgenic olive plants have been acclimated in the greenhouse and are currently being analyzed at the molecular level.

RETRACTED ARTICLE: Transgenic ramie [Boehmeria nivea (L.) Gaud.]: factors affecting the efficiency of Agrobacterium tumefaciens-mediated transformation and regeneration

In the present study, an efficient Agrobacterium-mediated gene transformation system was developed for ramie [Boehmeria nivea (L.) Gaud.] based on the examinations of several factors affecting plant transformation efficiency. The effects of Agrobacterium cell density, acetosyringone, co-cultivation temperature, co-cultivation duration, co-cultivation photoperiod and pH on stable transformation were evaluated. Agrobacterium at a concentration of OD = 0.5–0.8 improved the efficiency of transformation. Concentration of acetosyringone at 50 mg/L during co-cultivation significantly increased transformation efficiency. Co-cultivation at 20°C, in comparison to 15, 25 and 28°C, consistently resulted in higher transformation frequencies. A relatively short co-cultivation duration (3 days) was optimal for ramie transformation. Co-cultivation medium at pH 5.9 and co-cultivation in darkness both improved the transformation efficiencies of ramie. An overall scheme for producing transgenic ramie is presented, through which an average transformation rate from 10.5 to 24.7% in five ramie varieties was obtained. Stable expression and integration of the transgenes were confirmed by histochemical GUS assay, kanamycin painting assay, PCR and Southern blotting. This optimized transformation system should be employed for efficient Agrobacterium-mediated transformation of ramie.

Influence of Flow Conditions and System Geometry on Nitrate Use by Benthic Biofilms: Implications for Nutrient Mitigation

The effects of substratum geometry and overlying velocity on nitrate use by periphyton were assessed. Periphyton was cultivated at an average current velocity of 0.5 cm s(-1) in laboratory mesocosms (120 cm long, 60 cm wide) on polyethylene nets of three different geometries, "1-lay er", "3-layer", and "bedform" structures, overlaying a thin bed of sand. Bulk nitrate use was then measured as the reduction of nitrate concentration in the overlying water under average velocities of 0.005, 0.05, and 0.5 cm s(-1). Periphyton structural characteristics were quantified as algal/bacterial biomass, algal species composition, and bacterial densities. Accrual of microbial biomass increased monotonically with increasing benthic net surface area, with upper sections of structures supporting the highest biomass. Maximum rates of nitrate removal were measured in the bedform geometry at intermediate velocity (173 mg NO3-N m(-2) d(-1)), and the lowest was measured with 1-layer geometry at the fastest velocity (11 mg NO3-N m(-2) d(-1)). Oxygen microprofiles within biofilms demonstrated that hydrodynamic conditions and benthic structure both play a key role in the regulation of microbial processing of nitrate delivered from the water column by promotion of denitrification in downstream sections of bedform substrata. Interactions between hydrodynamic conditions and substratum geometry are expected to regulate microbial activity in all surficial natural and engineered environments and must be parameterized to forecast long-term average biochemical transformation rates in rivers and other dynamic aquatic systems.

Biophysicochemical process coupling controls nitrogen use by benthic biofilms

A combination of macroscale and microscale observations was used to show that the interplay between hydrodynamic transport, local chemical conditions, and microbial metabolism controls nitrate use by benthic microbial communities. While it is usually assumed that interfacial transport and nutrient removal both increase monotonically with the velocity of the overlying flow, in laboratory flume experiments we observed substantially greater bulk nitrate removal under slower velocities (0.05 and 0.5 cm s−1) than under a faster velocity (5 cm ss−1), with the greatest rate of nitrate removal occurring under the intermediate flow condition. These results demonstrate that hydrodynamic control of solute transport, specifically here the flux of oxygen and nitrate from the water column to the benthic microbial community, causes facultative bacteria to shift between anaerobic and aerobic metabolism under different flow conditions. Aerobic metabolism is promoted by more rapid hydrodynamic transport conditions, while anaerobic metabolism is favored under low‐transport conditions. This type of coupling is expected to regulate microbial activity in all surficial sedimentary environments and must be parameterized in order to forecast long‐term average biochemical transformation rates in rivers and other dynamic aquatic systems.