Effects of three active ingredients on soil bacterial communities

The use of bioactive molecules for medical purposes is an important field of industrial activity and gives rise to release a large amount of chemicals in the environment. Industrial farm producing such molecules are suitable places to investigate the possible release of contaminants and their effects on biological communities. Soil microbes are directly affected when active molecules reach environment and thereafter they are very suitable as experimental tool. Side effects on humans and animals require specific toxicological studies, to which the knowledge deriving from soil microorganisms can give benefits (Boxall, 2004). Our research has been focused on the assessment of the effects of glimepiride, ramipril and pentoxifillyne, three active ingredients belonging to different therapeutic classes, on the functional and genetic diversity of the bacterial community in soil. Soil samples of different physical and chemical characteristics were collected from areas exposed to the risk of contamination by active ingredients inside a pharmaceutical farm estate (I) and from a control (E). Aliquots of each soil (I, E) were placed separately in plastic boxes and amended respectively with 0, 5, 50, 500 mg/Kg of each active ingredient. Changes in microbial diversity were monitored by culturedependent methods: bacterial enumeration (CFU), community level physiological profiles (CLPPs) measured by Biolog Ecoplate™ and a culture-independent technique DGGE, over a period of 3 months. The DGGE profiles of treated and untreated soils were different during the incubation period. In particular, ramipril treated soils showed a noticeable decrease in bands number respect to the control soils after 60 and 90 days. At 90 days, CFU isolated from soils (E), treated with three active ingredients were significantly smaller (P < 0.05) than the ones from control; soils (I) treated with pentoxifillyne (50 and 500 mg/Kg) and ramipril (5 mg/Kg) on the contrary gave higher CFU figures. Results of cluster analysis performed on Biolog data showed that functional abilities of the soil microbial communities were altered by application of the active ingredients. In particular, a) CLPPs of the glimepiride and ramipril treatments, especially 500 mg/Kg, differed from the control; b) CLPPs of pentoxifillyne treated soils taken from pharmaceutical farm (I) were sharply different from control than pentoxifillyne treated soil taken outside (E). Soil characters were influential on bacterial community response to active ingredients. Differences were found on substrate utilization in the Biolog Ecoplate™ between treated and untreated soil, mainly as to the intensity of substrate assimilation. In conclusion, this study shows that both genetic and metabolic potential of soil microbial communities are affected by application of these active ingredients.