دانلود رایگان مقاله اثر کبالت و نانوذرات نقره و یونها بر سلامت کرم Lumbricus rubellus

Abstract

The aim of this study was to investigate the impact of silver and cobalt, supplied both as ions and nanoparticles (Ag+ , Co2+, AgNPs, CoNPs) through contaminated food to earthworms (Lumbricus rubellus), on their health as well as on microbial community of both soil and earthworm faeces. Earthworms and microbes were exposed to the contaminants in laboratory microcosms with artificial soil. Contaminants were supplied once a week for 5 weeks by spiking them on horse manure. The accumulation of CoNPs and Co2+ in earthworm tissues was two and three times greater than AgNPs and Ag+ , respectively. Except for AgNPs, contaminants significantly affected microbial community structure of earthworm faeces by increasing G- bacteria, thus also increasing the bacteria/fungi ratio while decreasing the G+/G- bacteria ratio. Such shift was also reflected on soil microbial community, thus suggesting a close relationship between microbial community of soil and of earthworm faeces. Neither of the Co treatments affected soil microbial basal respiration whereas they increased the microbial biomass specific respiration or metabolic quotient, suggesting some stress induction on soil microorganisms. Earthworm health was strongly affected as revealed by the reduced fluidity of fatty acids extracted from the body tissues. In addition, the histological investigations, after the depuration period, showed positive results about the NPs toxicity. In particular, TUNEL-positive nuclei in epidermis and in peritoneum, suggest the presence of toxicosis.The ESEM-EDS technique revealed the presence of Ca-P spherules (calcification) between mouth and clitellum of earthworms fed with Co2+ contaminated food.

5. Conclusions

The addition of polluted horse manure to soil as food for earthworms changed the microbial community structure in earthworm faeces and, in turn, such changes were reflected on Fig. 3. Histology of L. rubellus, body wall, longitudinal section from the zone just posterior to clitellum. a) Hematoxylin-Eosin of a control specimen. The body wall is made up by epidermis (E), circular muscle layer (CM), longitudinal muscle layer (LM), and a layer of cells which line the coelomic cavity (C), named peritoneum. b) TUNEL and DAPI staining in control specimen. An apoptotic nucleus is detectable in the muscle (see frames with a higher magnification and split fluorescence channels), close to a seta, which is autofluorescent. c) TUNEL and DAPI staining in a specimen treated with Ag+ and depurated. No apoptosis is detected in epidermis (E), nor in the peritoneum lining the coelomic cavity (C), while scattered, rare apoptotic nuclei are present in the muscle (M) (see frames with an higher magnification and split fluorescence channels). d) TUNEL and DAPI staining in a specimen treated with AgNPs and depurated. Numerous apoptotic nuclei are detectable in the peritoneum (arrow) lining the coelomic cavity (C). e) TUNEL and DAPI staining in a specimen treated with Co2+ and depurated. f) TUNEL and DAPI staining in a specimen treated with CoNPs and depurated. Numerous apoptotic nuclei are detectable in epidermis (arrowhead) lining the coelomic cavity (C). Scale bars: 100mm. L. Vittori Antisari et al. / Applied Soil Ecology 108 (2016) 62–71 69 soil microbial biomass and community structure, thereby suggesting a close relationship between the microbial communities of soil and of earthworm faeces. Our results suggest a significant impact of contaminants, supplied via contaminated food to earthworms, on bacterial community structure after its passage through the digestive tract whereas fungi were not affected. PLFAs biomarkers suggested that G- bacteria are those more impacted by contaminants. The absence of changes in microbial basal respiration may suggest a functional redundancy of soil microorganisms. However, such an aspect should be studied more comprehensively as slight but significant shifts in specific respiration rate were observed in Co treatments, indicating some stress on microbial biomass. The investigation of L. rubellus health after four weeks of depuration evidenced the onset of disorders at different degrees in all treatments. The Ca/P ratio in earthworm tissues could become an early biomarker of earthworm health. To our best knowledge, this study is the first concerning the effect of Ag and Co on the relationship between soil microorganisms and L. rubellus. Further studies are needed to better understand the mechanistic way of Ag and Co effects on soil microorganisms and on its bioaccumulation in L.rubellus, as well as the identifications of biomarkers able to describe the nano-biointeractions.