RESUMEN
We applied a screening-level phytotoxicity assay to evaluate the effects of 10 antibiotics (at concentrations ranging from 1 to 10,000 µg/L) on germination and early plant growth using three plant species: lettuce (Lactuca sativa), alfalfa (Medicago sativa), and carrot (Daucus carota). The range of phytotoxicity of the antibiotics was large, with EC25s ranging from 3.9 µg/L to >10,000 µg/L. Chlortetracycline, levofloxacin, and sulfamethoxazole were the most phytotoxic antibiotics. D. carota was the most sensitive plant species, often by an order of magnitude or more, followed by L. sativa and then M. sativa. Plant germination was insensitive to the antibiotics, with no significant decreases up to the highest treatment concentration of 10,000 µg/L. Compared with shoot and total length measurements, root elongation was consistently the most sensitive end point. Overall, there were few instances where measured soil concentrations, if available in the publicly accessible literature, would be expected to exceed the effect concentrations of the antibiotics evaluated in this study. The use of screening assays as part of a tiered approach for evaluating environmental impacts of antibiotics can provide insight into relative species sensitivity and serve as a basis by which to screen the potential for toxic effects of novel compounds to plants.
Asunto(s)
Antibacterianos/toxicidad , Germinación/efectos de los fármacos , Raíces de Plantas/efectos de los fármacos , Contaminantes del Suelo/toxicidad , Bioensayo , Daucus carota/efectos de los fármacos , Daucus carota/crecimiento & desarrollo , Daucus carota/metabolismo , Lactuca/efectos de los fármacos , Lactuca/crecimiento & desarrollo , Lactuca/metabolismo , Medicago sativa/efectos de los fármacos , Medicago sativa/genética , Medicago sativa/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Contaminantes del Suelo/metabolismoRESUMEN
Pharmaceuticals and personal care products may enter the terrestrial environment through the amendment of agricultural soils with manure or biosolids with potential impacts on beneficial soil microbe populations. The beneficial symbiotic relationship between most plant species and arbuscular mycorrhizal fungi is a primary determinant of plant health and soil fertility. As such, there is increasing recognition of the need to study the impacts of anthropogenic stressors on plant-microbe interactions in soil ecotoxicology studies and risk assessment. A case study exploring the use of root-organ cultures to evaluate the effects of 12 common veterinary and human-use pharmaceuticals on the arbuscular mycorrhizal fungus, Glomus intraradices grown on Daucus carota root-organ cultures is presented. The bioassays were conducted over a 28-day exposure period at concentrations up to 1000microgl(-1). Root length and the fungal endpoints of hyphal growth and spore production were evaluated weekly during the study. Sulfamethoxazole and atorvastatin were the most phytotoxic compounds with EC50 values of 45microgl(-1) and 65microgl(-1), respectively. Three compounds exhibited selective mycotoxicity, whereby the fungal symbiont was adversely affected at concentrations significantly less than that calculated for root length. The EC50 for G. intraradices hyphal length was 45microgl(-1) for doxycycline, while carbamazepine and 17-alpha-ethynyl estradiol targeted spore production with EC50 values of 113 and 116microgl(-1), respectively. The assay results indicate that the root lengths responded quickly to the presence of phytotoxic pharmaceuticals in the culture medium. Hyphal length is a sensitive endpoint after 21 days exposure, while spore production requires 28 days exposure before significant differences could be detected. Root-organ cultures provide an effective means to evaluate chemical stressors on arbuscular mycorrhizal fungi and can be used to screen for root-based phytotoxicity.
Asunto(s)
Micorrizas/efectos de los fármacos , Preparaciones Farmacéuticas , Raíces de Plantas/efectos de los fármacos , Bioensayo , Micorrizas/metabolismo , Raíces de Plantas/metabolismo , Raíces de Plantas/microbiologíaRESUMEN
The effects of monensin, an antibiotic widely used in the poultry and beef industry, were evaluated on zooplankton community structure and population dynamics. Monensin was added to 12 000 L aquatic microcosms as a single treatment at concentrations ranging from 0.5 to 500 microg/L, and they were evaluated over a 50 day period. Changes in the zooplankton assemblage were evaluated by principal response curves (PRC), while changes in abundance and species richness were evaluated by analysis of variance (ANOVA). Monensin did not significantly affect community structure. However, significant changes within specific taxonomic groups were observed with decreases in the abundance of Rotifera and Copepoda nauplii and in the richness of Rotifera and Cladocera. Concentration-dependent increases in Ostracoda abundance were also observed. Changes in chlorophyll-a concentrations within the microcosms over the course of the study indicated that the changes in zooplankton populations were the indirect result of the effects of monensin on the algal community. Monensin concentrations measured in surface waters were 40 times lower than the determined no-observable effect concentration (NOEC) of 50 microg/L and do not likely present a risk to zooplankton.