Approved Abstracts

Impact of eight commonly used antibiotics on the physiological profile of the soil microbiota.



Author(s): N. Ferrando; C. Gan; G. Lorca; D. Ballestero; E. Langa; E. Terrado; MR. Pino-Otín ;
Presenter: Natalia Ferrando

Due to the widespread use of antibiotics, they are eventually introduced into the environment via untreated and treated sewage and biosolids, as the primary sources. Antibiotics deserve special attention as environmental contaminants because they are designed to specifically interfere with biological processes at low concentrations, and to be persistent. Furthermore, the spread of antibiotics in soil and water ecosystems has led to an increase in resistant bacteria, which is considered a worrying topic by the World Health Organization (WHO).
In this study, we assessed the effect of 8 widely consumed antibiotics on the physiology of soil microbial communities from an ecological crop field. Biolog EcoPlates®, containing 31 of the most common carbon sources found in forest and crop soils, were used to calculate both the average well color development (AWCD), as an indicator of the entire capability to degrade carbon sources, and the diversity of carbon source utilization, as an indicator of the physiological diversity. Previously, Minimum Inhibitory Concentration (MCI) of such antibiotics were tested on 14 gram positive and gram-negative bacteria with clinical or industrial interest, in order to be able to interpret later their bactericidal effect on the soil microbiota.

Our results showed that all the tested antibiotics impact on microbial communities by altering their ability to metabolize different carbon sources, thus affecting the metabolic diversity of the soil community. The AWCD obtained for the lowest concentrations of antibiotic solutions, 0,1 µg/mL, resembled those of the soil sample control for all the antimicrobials tested. Same behavior was observed with metabolite consumption, fairly like the control.

On the contrary, 100 µg/mL and 1000µg/mL antibiotic concentrations proved to be a major hazard to soil microbiota as both, the AWCD and metabolites intake, reduced drastically. Chloramphenicol and tetracycline were found to be fatal, affecting mostly to the polymer metabolites, while aminoglycosides focused on amino acids and ketonic acids. Streptomycin surprisingly increased vastly the consumption of amines and amides, while a large reduction of the rest of the metabolites was noted. Betalactamics’ AWCD (penicillin, amoxicillin, and ampicillin) showed little differences for these two higher concentrations, and both had less activity in the metabolic profile. Furthermore, a correlation between the effect and exposition hours to the antibiotic solutions was accounted for.

Although the acute effects will not be frequent, our results suggest that the repeated contamination of agricultural soils with biosolids or sludges containing antibiotics residuals may adversely affect the soil ecological functions.


Keywords: Ecotoxicoloy; Microbiology; Antibiotics

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