Abstract
Cefuroxime (XM), the most commonly prescribed antibiotic from the cephalosporin group, may cause changes in the structure of the soil microbial community, and these changes may also be reflected in the alteration of its functionality. Therefore, due to the lack of studies on this topic, the scope of this study was to assess the functional diversity and catabolic activity of the microbial community in soil treated with XM (1 mg/kg and 10 mg/kg soil) using the community-level physiological profile (CLPP) approach during a 90-day experiment. In addition, the effect of antibiotic-resistant Pseudomonas putida strain MC1 (Ps) was also evaluated. The resistance/resilience concept and multifactorial analysis were used to interpret the data. The results showed that the introduction of XM and/or Ps into the soil caused changes in the catabolic activity and functional diversity of the microbial community. A decrease in the values of the CLPP indices (i.e., microbial activity expressed as the average well-color development (AWCD), substrate richness (R), the Shannon-Wiener (H) and evenness (E) indices and the AWCD values for the six carbon substrate groups) for the XM-treated soil was generally detected up to 30 days. In turn, at the same time, the activity measured in the Ps-inoculated soil was higher compared to the control soil. A stimulatory effect of XM at 10 mg/kg (XM10) and XM10+Ps on the utilization pattern of each substrate group was found at the following sampling times (days 60 and 90). The AWCD values for the utilization of amines, amino acids, carbohydrates, carboxylic acids, miscellaneous compounds and polymers for these treatments were found to be up to 2.3-, 3.1-, 2.3-, 13-, 3.4- and 3.3-fold higher compared to the values for the nontreated control, respectively. The resistance of the CLPP indices and the AWCD values for the carbon substrate groups were categorized as follows: E > H > R > AWCD and amino acids = carbohydrates > polymers > amines > miscellaneous > carboxylic acids, respectively. The results suggest a low initial resistance of the soil microbial community to XM and/or Ps, and despite the short-term negative effect, the balance of the soil ecosystem may be disturbed.
Highlights
Antibiotics belong to a group of pharmaceuticals that have recently been excessively used, leading to their accumulation in various parts of the environment, including the soil
The results of this study showed that the introduction of XM and/or strain MC1 to the soil caused changes in the catabolic activity of the microbial community analyzed, and these changes were demonstrated by a significant decrease (p < 0.05) in the community-level physiological profile (CLPP) indices for the XM-treated soil generally up to 30 days
The XM and XM+putida strain MC1 (Ps) treatments contributed to a significant decrease (p < 0.05) in the average well-color development (AWCD) values, and this decrease accounted for 26–68%, 6–31% and 9–22% of the control values on days 1, 15 and 30 of the experiment, respectively (Figure 2A)
Summary
Antibiotics belong to a group of pharmaceuticals that have recently been excessively used, leading to their accumulation in various parts of the environment, including the soil. It has been shown that even very low concentrations of antibiotics can cause changes in the genome of microorganisms and lead to the transfer of resistance genes between individual members of an exposed population of microorganisms. Microorganisms naturally present in the soil can be a source of resistance genes that can be transferred to other microorganisms such as human and animal pathogens [21,22,23,24] In addition to this effect, antibiotics belonging to different classes may adversely affect the soil microflora, possibly manifesting themselves in the change of their structure [15,25,26,27] and functionality [6,9,28,29,30]. Data on the effect of antibiotics on soil microorganisms are varied and include results related to the impact on individual species and whole populations of microorganisms obtained on the basis of biochemical and genetic indices analyses [9,30,31,32,33]
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