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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.

Plant–microbial relations have not yet been fully disclosed in natural or seminatural ecosystems, nor in novel ecosystems developing spontaneously on post-coal mine heaps. The aim of this study was to determine which factor, biotic (plant taxonomic diversity vs. plant functional diversity) or abiotic (physicochemical substrate parameters), affects the biomass of soil microbial communities the most, as well as soil in situ respiration in novel ecosystems. The study was carried out on unreclaimed plots selected according to four different combinations of taxonomic and functional plant diversity. Additionally, plots on a reclaimed heap served as a comparison between the two management types. The biomass of several soil microbial groups was analysed using phospholipid fatty acids profiles. We detected that soil microbial biomass was more impacted by abiotic parameters (explaining 23% of variance) than plant diversity (explaining 12% of variance). Particularly, we observed that substrate pH was the most important factor shaping microbial community biomass, as shown in the RDA analysis. The highest microbial biomass was found in plots with low taxonomic and functional diversity. This finding can be explained by the fact that these plots represented a more advanced phase of vegetation development in the early stages of plant succession.