Ultimate biodegradation and elimination of antibiotics in inherent tests

The biodegradation and elimination of antibiotics in municipal wastewater treatment plants is of particular concern because sewage is the main exposure route for antibiotics used in human medicine. The inherent biodegradability of 17 antibiotics was determined in a combined test design based on the Zahn-Wellens test (OECD 302 B, 1992) and the CO2-evolution test (OECD 301 B, 1992). CO2 Evolution test (Modified Sturm test). OECD Guideline for the Testing of Chemicals, Paris). Only benzylpenicillin sodium salt (Penicillin G) proved to be ultimately biodegradable, reaching ThCO2 degradation extents of 78-87%. Among the others, only amoxicillin, imipenem and nystatin showed certain ultimate biodegradation in few of the parallel flasks and can be regarded as partially biodegradable with formation of stable metabolites. The DOC-elimination of tetracycline-HCl showed a typical degradation curve starting with 18% and reaching the plateau phase at 80% after 21 days. Nevertheless, the CO2-evolution measured in parallel did not support the data, indicating that the time needed for reaching the adsorption equilibrium was underestimated. Several other antibiotics showed considerable DOC-elimination in the inherent test while only minor incidences of ultimate biodegradation were observed. The combination of CO2-evolution and DOC-elimination is a suitable instrument for assessing the behaviour of chemicals within one test. It enables one to assess both inherent ultimate biodegradability and DOC-elimination by sorption. The applicability of the test is limited to substances with a moderate toxicity.     

Earth stewardship: Shaping a sustainable future through interacting policy and norm shifts

Transformation toward a sustainable future requires an earth stewardship approach to shift society from its current goal of increasing material wealth to a vision of sustaining built, natural, human, and social capital—equitably distributed across society, within and among nations. Widespread concern about earth’s current trajectory and support for actions that would foster more sustainable pathways suggests potential social tipping points in public demand for an earth stewardship vision. Here, we draw on empirical studies and theory to show that movement toward a stewardship vision can be facilitated by changes in either policy incentives or social norms. Our novel contribution is to point out that both norms and incentives must change and can do so interactively. This can be facilitated through leverage points and complementarities across policy areas, based on values, system design, and agency. Potential catalysts include novel democratic institutions and engagement of non-governmental actors, such as businesses, civic leaders, and social movements as agents for redistribution of power. Because no single intervention will transform the world, a key challenge is to align actions to be synergistic, persistent, and scalable.     

Seasonal source influence on river mass flows of benzotriazoles

The anticorrosive agents 1H-benzotriazole (1H-BT), 4-methyl-1H-benzotriazole (4 Me-BT) and 5-methyl-1H-benzotriazole (5 Me-BT), which are usually added to dishwasher detergents, automotive antifreeze formulations and aircraft de-icing/anti-icing fluids (ADAFs), were measured in river water. Samples were collected from 15 sampling sites in the mainstream and selected tributaries of a medium-sized catchment area during summer and winter periods. The aim of this study was to assess a seasonal source influence on mass flows of benzotriazoles (BTs). The study area was representatively selected for an area with a possible influence of airport surface runoff. River discharge measurements were also performed. Moreover, BT concentrations were measured in an anti-icing and a de-icing fluid used at German airports as well as in several dishwasher detergents. The highest concentrations of all three compounds in river water were measured during the winter seasons. The maximum BT mass flows were calculated for all three substances in January when the mean monthly air temperature was the lowest; mass flows were the lowest in July when the mean monthly air temperature was the highest. A significant seasonal influence on BT mass flows in river water was observed for monitoring stations with a possible influence of airport surface runoff and for sampling locations where such an influence could be excluded. This indicates an input of BTs from other temperature-dependent applications, e.g. the use of antifreeze formulations in automotive windscreen wiper or cooling systems. 1H-BT was detected in two dishwasher tablets; 4 Me-BT and 5 Me-BT were not detected. BTs were measured in the anti-icing fluid with concentrations of 715 ng g(-1) (1H-BT), 1425 ng g(-1) (4 Me-BT) and 536 ng g(-1) (5 Me-BT); none of the BTs were detected in the de-icing fluid. Distribution patterns of BTs in ADAF and dishwasher detergents differed from those in river water.     

Effect of sulfide on the cytotoxicity of arsenite and arsenate in human hepatocytes (HepG2) and human urothelial cells (UROtsa)

Arsenic, a common poison, is known to react with sulfide in vivo, forming thioarsenates. The acute toxicity of the inorganic thioarsenates is currently unknown. Our experiments showed that a fourfold sulfide excess reduced acute arsenite cytotoxicity in human hepatocytes (HepG2) and urothelial cells (UROtsa) significantly, but had little effect on arsenate toxicity. Speciation analysis showed immediate formation of thioarsenates (up to 73 % of total arsenic) in case of arsenite, but no speciation changes for arsenate. Testing acute toxicity of mono- and trithioarsenate individually, both thioarsenates were found to be more toxic than their structural analogue arsenate, but less toxic than arsenite. Toxicity increased with the number of thio groups. The amount of cellular arsenic uptake after 24 h corresponded to the order of toxicity of the four compounds tested. The dominant to almost exclusive intracellular arsenic species was arsenite. The results imply that thiolation is a detoxification process for arsenite in sulfidic milieus. The mechanism could either be that thioarsenates regulate the amount of free arsenite available for cellular uptake without entering the cells themselves, or, based on their chemical similarity to arsenate, they could be taken up by similar transporters and reduced rapidly intracellularly to arsenite.     

Isolation and characterization of biarylic structure-degrading yeasts: hydroxylation potential of dibenzofuran

Yeast communities from heavily polluted sediments that received the discharge from oil refineries and other industries were studied. Yeast species were isolated from these sediments and their ability to degrade dibenzofuran were determined. Twenty-four different yeast strains were isolated and cultured on aromatic medium; two Candida krusei strains. Candida tenuis, Candida tropicalis, two Pichia anomala strains, Pichia haplophila, two Rhodotorula glutinis strains, Rhodotorula mucilaginosa, two Trichosporon pullulans strains and Yarrowia lipolytica were able to hydroxylate dibenzofuran. Three metabolites were identified by HPLC analysis: 3-hydroxydibenzofuran was in all the cases the most abundant isomer, and while 4-hydroxydibenzofuran was also common, 2-hydroxydibenzofuran was detected in very small quantities and with few species. In the R. glutinis and Y. lipolytica cultures a ring cleavage product was also found. While in the R. gluttinis assays the hydroxydibenzofuran was detected earlier, at 2 days' incubation time, in the other yeast experiments they were observed at the 4-5th incubation days with the maximum amounts at the 7th day. Our results confirmed the ability of autochthonous yeast species to hydroxylate dibenzofuran and to cleave the rings, and it is the first report for C. krusei, C. tenuis, P. anomala, P. haplophila and R. mucilaginosa. The ecological relevance of this study is based on the fact that dibenzofuran is a xenobiotic not easily transformed, so the catabolic activities observed in authochonous yeasts contribute to broadening the biodegradable substrate spectrum.     

Colony performance in honeybees (Apis mellifera capensis Esch.) depends on the proportion of subordinate and dominant workers

Summary Individual worker dominance correlated with trophallactic behavior, which affects several social behaviors related to colony fitness, shows a high genetic variance in worker bees. In a bioassay we tested trophallactic behavior of workers and selected dominant (receiving) and subordinate worker bees (offering) of Apis mellifera capensis to establish genetic lines of both kinds. Queenright test colonies were experimentally composed of 100% subordinate workers, 100% dominant workers, 50% dominant plus 50% subordinate workers, and 100% hybrid workers from the two genetic lines. The chosen test parameters were brood-rearing, comb building and hoarding behavior. In all cases, the colonies of pure subordinate bees showed the best colony performance, whereas the colonies composed of only dominant bees were nearly unproductive. The mixed colonies (50% dominant + 50% subordinate) ranked in the middle and did not differ significantly from the hybrid colonies. The results indicate that colony performance under queenright conditions depends on the proportion of subordinate workers. This result supports a selection model based on the combination of individual selection and on group selection at the colony level, which explains the high genetic variance of individual worker reproduction.     

Homing pigeons (<Emphasis Type="Italic">Columba livia</Emphasis> f. <Emphasis Type="Italic">domestica</Emphasis>) can use magnetic cues for locating food

An experimental group of homing pigeons (Columba livia f. domestica) learned to associate food with a magnetic anomaly produced by bar magnets that were fixed to the bowl in which they received their daily food ration in their home loft; the control group lacked this experience. Both groups were trained to search for two hidden food depots in a rectangular sand-filled arena without obvious visual cues; for the experimental birds, these depots were also marked with three 1.15 × 10⁶ μT bar magnets. During the tests, there were two food depots, one marked with the magnets, the other unmarked; their position within the arena was changed from test to test. The experimental birds searched within 10 cm of the magnetically marked depot in 49% of the test sessions, whereas the control birds searched there in only 11% of the sessions. Both groups searched near the control depot in 11 and 13% of the sessions, respectively. The significant preference of the magnetically marked food depot by the experimental birds shows that homing pigeons cannot only detect a magnetic anomaly but can also use it as a cue for locating hidden food in an open arena.