Doxycycline biodegradation by symbiotic bacteria from Diabrotica speciosa (Coleoptera: Chrysomelidae)

Antibiotics constitute one of the most widely used groups within pharmaceuticals, being employed not only for the treatment and prevention of human diseases, but also in the promotion of animal growth and improvement1,2. However, improper use of these substances can lead to negative consequences, such as the acquisition of resistance and contamination of the environment, once an important part of antibiotics is not fully metabolized, being excreted by humans and animals in wastewater, which are soon spread in the agricultural soil fertilized with animal manure, generating contamination in the soil, water and the biomagnification of the trophic chains3,4. On the other hand, bacteria present in the gastrointestinal tract of pest insects are able to provide "new metabolic powers" resulting new behaviours and/or habilities to the host, such as promoting resistance mechanisms for xenobiotic substances through the biodegradation of these ones.5 Two bacterial strains were selected after we evaluated the tolerance of the strains in the presence of the antibiotic and biodegradation potential, in a rich and deficient nutrient environment (growth media). We observed that the species Enterobacter cloacae and Stenotrophomonas maltophila could be grown in broth containing doxycycline. The degradation kinetics of the bacterial strains and their respective co-cultivos were evaluated, presenting a decrease in the doxycycline recovery in saline medium, suggesting the biodegradation of the antibiotic by the bacterium E. cloacae with recovery of 58.0±0.2% of analyte after 96 h. In rich medium, E. Cloacae presented a biodegradation rate of 23% in the period of 96 h. In its turn, S. maltophila showed an good cellular growth in both evaluated means, however, in both cases the recovery of doxycycline was almost total inside the period of evaluation.