No description available.

Engineered nanomaterials (ENMs) have become ubiquitous in consumer products and industrial applications, and consequently the environment. Much of the environmentally released ENMs are expected to enter terrestrial ecosystems via land application of nano-enriched biosolids to agricultural fields. Among the organisms most likely to encounter nano-enriched biosolids are the key soil bacteria known as plant growth promoting rhizobacteria (PGPR). I reviewed what is known concerning the toxicological effects of ENMs to PGPR and observed the need for high-throughput methods to evaluate lethal and sublethal toxic responses of aerobic microbes. I addressed this issue by developing high-throughput microplate assays which allowed me to normalize oxygen consumption responses to viable cell estimates. Oxygen consumption is a crucial step in cellular respiration which may be examined relatively easily along with viability and may provide insight into the metabolic/physiological response of bacteria to toxic substances. Because many of the most toxic nanomaterials (i.e. metal containing materials) exhibit some level of ionic dissolution, I first developed my methods by examining metal ion responses in the PGPR, Bacillus amyloliquefaciens GB03. I found this bacterium exhibits differential oxygen consumption responses to Ag+, Zn2+, and Ni2+. Exposure to Ag+ elicited pronounced increases in O2 consumption, particularly when few viable cells were observed. Also, while Ni2+ and Zn2+ are generally thought to induce similar toxic responses, I found O2 consumption per viable cell was much more variable during Ni2+ exposure and that Zn2+ induced increased O2 utilization to a lesser extent than Ag+. Additionally, I showed my method is useful for probing toxicity of traditional antibiotics by observing large increases in O2 utilization in response to streptomycin, which was used as a positive control due to its known effects on bacterial respiration. After showing the utility of my method for examining metal ion responses in a single species of PGPR, I investigated the toxicity of silver ENMs (AgENMs) and ions to three PGPR, B. amyloliquefaciens GB03, Sinorhizobium meliloti 2011, and Pseudomonas putida UW4. The ENM exposures consisted of untransformed, polyvinylpyrrolidone coated silver ENMs (PVP-AgENMs) and 100% sulfidized silver ENMs (sAgENMs), which are representative of environmentally transformed AgENMs. I observed species specific O2 consumption responses to silver ions and PVP-AgENMs. Specifically, P. putida exhibited increased O2 consumption across the observed range of viable cells, while B. amyloliquefaciens exhibited responses similar to those found in my first study. Additionally, S. meliloti exhibited more complex responses to Ag+ and PVP-AgENMs, with decreased O2 consumption when cell viability was ~50-75% of no metal controls and increased O2 consumption when cell viability was <50%. I also found the abiotically dissolved fraction of the PVP-AgENMs was likely responsible for most of the toxic response, while abiotic dissolution did not explain the toxicity of sAgENMs. My work has yielded a straightforward, cost-effective, and high-throughput method of evaluating viability and oxygen consumption in aerobic bacteria. I have used this method to test a broad range of toxic substances, including, metal ions, antibiotics, and untransformed and transformed ENMs. I observed species specific toxic responses to Ag+, PVP-AgENMs, and sAgENMs in PGPR. These results not only show the clear utility of the methodology, but also that it will be crucial to continue examining the responses of specific bacterial strains even as nanotoxicology, as a field, must move toward more complex and environmentally relevant systems.

O suprimento de proporções de nitrato (NO3-) e amônio (NH4+) no meio de crescimento pode otimizar o metabolismo e o crescimento do Panicum maximum. A toxidez de cobre (Cu) causa estresse oxidativo nas plantas, afetando o metabolismo, a fotossíntese e a produção de massa. Não há pesquisas associando proporções de NO3-/NH4+ no alívio do estresse por Cu em plantas. O objetivo foi avaliar o efeito da toxidez de Cu no metabolismo, nutrição mineral, fotossíntese e produção do capim tanzânia, assim como o papel de proporções de NO3-/NH4+ no alívio dessa toxidez. O delineamento experimental foi de blocos ao acaso em arranjo fatorial 3×4 com seis repetições, sendo três destinadas à avaliação dos atributos metabólicos e fisiológicos e outras três aos atributos nutricionais e produtivos. Os fatores empregados foram: proporções de NO3-/NH4+ (100/0; 70/30 e 50/50) combinadas com doses de Cu (0,3; 250; 500 e 1000 &mu;mol L-1) em solução nutritiva. Foram avaliados dois períodos de crescimento das plantas, sendo o primeiro com exposição ao Cu e o segundo sem exposição ao Cu. No primeiro corte as plantas supridas com 70/30 de NO3-/NH4+ e Cu de 1000 &mu;mol L-1 apresentaram maior concentração de Cu nas folhas recém-expandidas (LR) e maior acúmulo de Cu na biomassa, maior concentração de NH4+ nas LR, maior acúmulo de NH4+ na parte aérea, maior atividade da glutamina sintetase nas LR, maior concentração de prolina nas LR, maior atividade da enzima superóxido dismutase (SOD) nas partes do capim e menor produção de biomassa. No capim suprido com 100/0 de NO3-/NH4+ e Cu de 1000 &mu;mol L-1 foram obtidos menor concentração de Cu nas LR e menor acúmulo de Cu na parte aérea, mas a concentração e o acúmulo desse metal nas raízes foram incrementados mesmo nas mais baixas doses de Cu. As plantas crescidas com N na forma de NO3- ainda apresentaram maior concentração de NO3- nas LR, maior acúmulo de NO3- nas raízes, maior acúmulo de N total, maior atividade da nitrato redutase nas LR, maior condutância estomática e maior produção de biomassa. No capim recebendo 100/0 de NO3-/NH4+ também ocorreu menor atividade da SOD e menor concentração de prolina nas partes da planta. A concentração de malondialdeído foi menor na mais elevada dose de Cu, assim como a taxa de transpiração, a eficiência do fotossistema II, a taxa de transporte de elétrons e a taxa de assimilação de CO2. A atividade da catalase, guaiacol peroxidase, ascorbato peroxidase e glutationa redutase foram ativadas principalmente nas raízes, sendo maiores na mais elevada dose de Cu. A toxidez de Cu afeta negativamente o metabolismo, a nutrição mineral, a fisiologia e a produção do capim tanzânia, mas as proporções de NO3-/NH4+ alteram essa toxidez. O emprego de N na forma de NO3- é estratégia de maior potencial de uso em plantas com elevado estresse por Cu. Entretanto, a combinação de NO3- ao NH4+ no meio de crescimento em situação de moderado estresse por Cu é estratégica para maior fitoextração desse metal. / The supply of nitrate (NO3-) and ammonium (NH4+) proportions in the growth medium can optimize the metabolism and growth of Panicum maximum. Copper (Cu) toxicity causes oxidative stress in plants, affecting metabolism, photosynthesis and biomass production. There are no researchs associating proportions of NO3-/NH4+ for alleviating Cu stress toxicity. The objective was to evaluate the effect of Cu toxicity on metabolism, mineral nutrition, photosynthesis and dry matter production, as well as the role of NO3-/NH4+ proportions in alleviating such toxicity. The experimental was carried out in randomized complete block design in a 3×4 factorial with six replications. Three replications were used to evaluated metabolic and physiological attributes and other three to determine nutrition and productive attributes. The factors were three proportions of NO3-/NH4+ (100/0, 70/30 and 50/50) combined with four rates of Cu (0.3, 250, 500 and 1000 &mu;mol L-1) in nutrient solution. Two plant growth periods evaluated, being the first with plants exposure to Cu and the second without the exposure to Cu. In the first cut, plants supplied with 70/30 of NO3-/NH4+ proportions and Cu rates of 1000 &mu;mol L-1 showed high Cu concentration in recently fully expanded leaf laminae (LR), high Cu accumulation in the biomass, high NH4+ concentration in LR, high NH4+ accumulation in shoots, high glutamine synthetase activity in LR, higher proline concentration in LR, high superoxide dismutase (SOD) activity in parts of grass and low shoot dry matter production. In the grass supplied with 100/0 of NO3-/NH4+ and Cu of 1000 &mu;mol L-1 it was found a low Cu concentration in LR and low Cu accumulation in shoots, but the concentration and accumulation of this metal in roots were increased even in lower Cu rate. Plants supply with 100/0 of NO3-/NH4+ also showed high NO3- concentration in LR, high NO3- accumulation in roots, high N accumulation in shoots, high nitrate reductase activity in LR, high stomatal conductance and high biomass production. In the grass supplied with 100/0 of NO3-/NH4+, there was low SOD activity and low proline concentration in shoots. The concentration of malondialdehyde was low at the high Cu rate, as well as the transpiration rate, photosystem II efficiency, electron transport rate and CO2 assimilation rate. Catalase, guaiacol peroxidase, ascorbate peroxidase and glutathione reductase activities were activated mainly in roots, being high in high Cu rate. Cu toxicity negatively affects metabolism, mineral nutrition, physiology and dry matter productions of tanzania guineagrass, but NO3-/NH4+ proportions change this toxicity. The only use of NO3- in the N supply is a strategy of great potential to be use in plants with of high Cu stress. However, combinations of NO3- with NH4+ in the growth medium when plants suffer moderate Cu stress is strategic for great metal phytoextraction.

O suprimento de proporções de nitrato (NO3-) e amônio (NH4+) no meio de crescimento pode otimizar o metabolismo e o crescimento do Panicum maximum. A toxidez de cobre (Cu) causa estresse oxidativo nas plantas, afetando o metabolismo, a fotossíntese e a produção de massa. Não há pesquisas associando proporções de NO3-/NH4+ no alívio do estresse por Cu em plantas. O objetivo foi avaliar o efeito da toxidez de Cu no metabolismo, nutrição mineral, fotossíntese e produção do capim tanzânia, assim como o papel de proporções de NO3-/NH4+ no alívio dessa toxidez. O delineamento experimental foi de blocos ao acaso em arranjo fatorial 3×4 com seis repetições, sendo três destinadas à avaliação dos atributos metabólicos e fisiológicos e outras três aos atributos nutricionais e produtivos. Os fatores empregados foram: proporções de NO3-/NH4+ (100/0; 70/30 e 50/50) combinadas com doses de Cu (0,3; 250; 500 e 1000 &mu;mol L-1) em solução nutritiva. Foram avaliados dois períodos de crescimento das plantas, sendo o primeiro com exposição ao Cu e o segundo sem exposição ao Cu. No primeiro corte as plantas supridas com 70/30 de NO3-/NH4+ e Cu de 1000 &mu;mol L-1 apresentaram maior concentração de Cu nas folhas recém-expandidas (LR) e maior acúmulo de Cu na biomassa, maior concentração de NH4+ nas LR, maior acúmulo de NH4+ na parte aérea, maior atividade da glutamina sintetase nas LR, maior concentração de prolina nas LR, maior atividade da enzima superóxido dismutase (SOD) nas partes do capim e menor produção de biomassa. No capim suprido com 100/0 de NO3-/NH4+ e Cu de 1000 &mu;mol L-1 foram obtidos menor concentração de Cu nas LR e menor acúmulo de Cu na parte aérea, mas a concentração e o acúmulo desse metal nas raízes foram incrementados mesmo nas mais baixas doses de Cu. As plantas crescidas com N na forma de NO3- ainda apresentaram maior concentração de NO3- nas LR, maior acúmulo de NO3- nas raízes, maior acúmulo de N total, maior atividade da nitrato redutase nas LR, maior condutância estomática e maior produção de biomassa. No capim recebendo 100/0 de NO3-/NH4+ também ocorreu menor atividade da SOD e menor concentração de prolina nas partes da planta. A concentração de malondialdeído foi menor na mais elevada dose de Cu, assim como a taxa de transpiração, a eficiência do fotossistema II, a taxa de transporte de elétrons e a taxa de assimilação de CO2. A atividade da catalase, guaiacol peroxidase, ascorbato peroxidase e glutationa redutase foram ativadas principalmente nas raízes, sendo maiores na mais elevada dose de Cu. A toxidez de Cu afeta negativamente o metabolismo, a nutrição mineral, a fisiologia e a produção do capim tanzânia, mas as proporções de NO3-/NH4+ alteram essa toxidez. O emprego de N na forma de NO3- é estratégia de maior potencial de uso em plantas com elevado estresse por Cu. Entretanto, a combinação de NO3- ao NH4+ no meio de crescimento em situação de moderado estresse por Cu é estratégica para maior fitoextração desse metal. / The supply of nitrate (NO3-) and ammonium (NH4+) proportions in the growth medium can optimize the metabolism and growth of Panicum maximum. Copper (Cu) toxicity causes oxidative stress in plants, affecting metabolism, photosynthesis and biomass production. There are no researchs associating proportions of NO3-/NH4+ for alleviating Cu stress toxicity. The objective was to evaluate the effect of Cu toxicity on metabolism, mineral nutrition, photosynthesis and dry matter production, as well as the role of NO3-/NH4+ proportions in alleviating such toxicity. The experimental was carried out in randomized complete block design in a 3×4 factorial with six replications. Three replications were used to evaluated metabolic and physiological attributes and other three to determine nutrition and productive attributes. The factors were three proportions of NO3-/NH4+ (100/0, 70/30 and 50/50) combined with four rates of Cu (0.3, 250, 500 and 1000 &mu;mol L-1) in nutrient solution. Two plant growth periods evaluated, being the first with plants exposure to Cu and the second without the exposure to Cu. In the first cut, plants supplied with 70/30 of NO3-/NH4+ proportions and Cu rates of 1000 &mu;mol L-1 showed high Cu concentration in recently fully expanded leaf laminae (LR), high Cu accumulation in the biomass, high NH4+ concentration in LR, high NH4+ accumulation in shoots, high glutamine synthetase activity in LR, higher proline concentration in LR, high superoxide dismutase (SOD) activity in parts of grass and low shoot dry matter production. In the grass supplied with 100/0 of NO3-/NH4+ and Cu of 1000 &mu;mol L-1 it was found a low Cu concentration in LR and low Cu accumulation in shoots, but the concentration and accumulation of this metal in roots were increased even in lower Cu rate. Plants supply with 100/0 of NO3-/NH4+ also showed high NO3- concentration in LR, high NO3- accumulation in roots, high N accumulation in shoots, high nitrate reductase activity in LR, high stomatal conductance and high biomass production. In the grass supplied with 100/0 of NO3-/NH4+, there was low SOD activity and low proline concentration in shoots. The concentration of malondialdehyde was low at the high Cu rate, as well as the transpiration rate, photosystem II efficiency, electron transport rate and CO2 assimilation rate. Catalase, guaiacol peroxidase, ascorbate peroxidase and glutathione reductase activities were activated mainly in roots, being high in high Cu rate. Cu toxicity negatively affects metabolism, mineral nutrition, physiology and dry matter productions of tanzania guineagrass, but NO3-/NH4+ proportions change this toxicity. The only use of NO3- in the N supply is a strategy of great potential to be use in plants with of high Cu stress. However, combinations of NO3- with NH4+ in the growth medium when plants suffer moderate Cu stress is strategic for great metal phytoextraction.

No description available.

Thesis (M.Sc. Agriculture. (Soil Science)) -- University of Limpopo, 2022 / The constant growth experienced by the coffee industry has led to the high-volume production of coffee waste worldwide. One of the main coffee wastes is spent coffee ground (SCG), a residue obtained after the ground coffee beans are treated under pressure. The present study was aimed to investigate the utilization of SCG to amend soil physicochemical properties. This study was conducted at Greenhouse Biotechnologies Research Centre of Excellence, University of Limpopo, South Africa, where the effect of various rates of SCG concentration in volume percentage (vol%) was tested for a period of nine months. The spent coffee ground residue was collected from four restaurants at Haenertsburg, and the application rates were 0, 5, 10, 20, 30, 50 vol%. To evaluate the change in soil physicochemical properties overtime, the incubation period was divided into four test periods namely T1 was after a month, T3 after 3 months, T6 after 6 months, and T9 after 9 months. Physicochemical properties including nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), total organic carbon (TOC), cadmium (Cd), copper (Cu), nickel (Ni), zinc (Zn), and lead (Pb), pH, electrical conductivity (EC), C:N ratio, large macroaggregates (LM), small macroaggregates (sM), microaggregates (m), unaggregated silt and clay (s+c), mean weight diameter (MWD) and soil moisture content (SMC) were quantified at the end of each test period. Results revealed that the interaction between incubation periods and various SCG application rates significantly (p<0.05) increased pHw, EC, MWD, LM, base cations and significantly decreased TOC, heavy metals, SMC, m, and sM. Spent coffee ground increased pHw and EC of the soil at all application rates and reached a maximum of 7.8 units at T6 in treatment SCG-5 and 202.30 S/cm at T9 in treatment SCG-50 above the control respectively. Total organic carbon increased by 548% above control in the highest treatment (SCG-50) at T1, but, however, started declining from T3 in all treatments across the incubation period. SCG’s highest application rates (SCG-20 to SCG-50) reduced the soil Cd toxicity (threshold of >2 mg/kg), but however, also reduced the availability of micronutrients (Cu and Zn) during the incubation period. At T9, Mg, Ca, K, and P increased from mean values of 55.9 to 77.9, 40.9 to 62.2, 77.4 to 112, and 22.0 to 30.0 mg/Kg above control in treatments with high application rates. LM increased whilst sM, and m decreased across the incubation period in all treatments. MWD increased by 46% at T1 and reached its maximum of 56% at T6 in treatment SCG-50 above control. Additionally, there was a positive relationship between LM and MWD. Soil moisture content however increased to 60.26% at T1 in treatment SCG-50 and decreased from T3 across the incubation period. Spent coffee ground has the potential to be used as a liming material, a chelating agent, and for water management in semi-arid areas. It retains and cycles nutrients and improves soil structure through aggregation. However, research should be done in field conditions to access the effectiveness of this residue. / NRF

No description available.