Soil Enzymatic Activities and Microbial Community Structure in Soils Polluted with Tetracycline Antibiotics

Vanesa Santás-Miguel,Montserrat Díaz-Raviña,David Fernández-Calviño,Esperanza Álvarez-Rodríguez,Angela Martín,Ana Barreiro,Elena García-Campos,Avelino Núñez-Delgado,Manuel Arias-Estévez

doi:10.3390/agronomy11050906

Abstract

A laboratory experiment was performed to examine the medium-term influence of three tetracycline antibiotics (chlortetracycline, CTC; tetracycline, TC and oxytetracycline, OTC) at different concentrations in four agricultural soils with similar pH and different soil organic content. After a 42-days incubation period, three different soil enzymes (β-glucosidase, urease, and phosphomonoesterase) were estimated, as well as the phospholipid fatty acids (PLFAs). A residual effect was observed on all microbial parameters measured in the four soils affecting to the soil enzymes activity and soil microbial communities structure (PLFA pattern). A different microbial sensitivity to antibiotics was detected depending on both, soil type and the microbial property considered. Specifically, in general, no antibiotic effect or even a slight positive effect was observed for phosphomonoesterase and β-glucosidase enzyme activities, respectively, while a negative effect was detected for urease activity values, particularly at higher doses of the antibiotics in a soil with a low organic matter content. The principal component analysis performed with the PLFAs data obtained for all soil samples showed different microbial communities depending mainly on soil type, followed by the antibiotic added to the soil (CTC, TC or OTC) and, in a lesser extent, by its concentration. In general, the PLFA patterns showed similar microbial communities structure due to OTC and TC addition in comparison to the microbial communities structure of soil treated with CTC. These results could be environmentally relevant, especially as regards potential effects of antibiotics on the soil microbiome and hence on health risk assessment of these antibiotics in soils.

Highlights

IntroductionAntibiotics, for both veterinary and human medicine, have been widely used during the past decades and, upon reaching environmental compartments, are recognized as persistent contaminants
Four soils cultivated with potato–wheat rotation sampled in A Limia (Galicia, Spain) and no detectable concentrations of antibiotics were selected from a set of soils previously analyzed by Conce-Cid et al [1]
Our data showed that the effect of antibiotic addition on specific enzyme activities depended on both each microbial parameter and each soil type considered

Summary

Introduction

Antibiotics, for both veterinary and human medicine, have been widely used during the past decades and, upon reaching environmental compartments, are recognized as persistent contaminants. These emerging contaminants and their metabolites can enter the soil environment via animal manure, slurry, or sludge, used as organic fertilizer in agricultural or forest soils [1,2] or as an amendment for recovering degraded soils [3]. Ob-viously, investigations into this subject, focusing on potential risk assessment and searching for eventual environmental damage due to the presence of antibiotics in terrestrial ecosystems, are of high interest in the case of cultivated agricultural soils, due to the possible negative consequences for the food chain and human health, whereas they could have lower relevance for degraded forest soils. Limited information is still avai-lable related to the dynamics and behavior of antibiotics in soil agricultural ecosystems

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