Changes in microbial community structure and co-metabolism during the domestication of ofloxacin-degrading bacteria

Abstract

Background Ofloxacin (OFL) is stable and difficult to degrade. It has been detected in water, soil, and plants throughout the world. This study domesticated OFL-contaminated livestock manure soil with simplified carbon sources to identify flora capable of effectively degrading OFL. The changes in the structural composition and diversity of the microbial community and the functional abundance of the soil flora were analyzed by metagenome sequencing technology. The Biolog-ECO microplate method was used to study the utilization of 31 different carbon sources by selected bacteria and to identify the best co-metabolized carbon source for degradation. Results Amino acid carbon sources were more likely to cause significant changes in community structures with increasing OFL concentrations during the acclimation stage. The abundance of Sphingobacterium decreased from 69.23% to 9.84%, while Alcaligenes increased from 0.27% to 62.79%, and Stenotrophomonas increased from 11.63% to 33.33%, becoming the dominant genus. The results suggested that Stenotrophomonas and Alcaligenes were potential candidate bacteria for the degradation of quinolone antibiotics, such as OFL. Compared with the first stage of acclimation, there was an 87% increase (the concentration was 30 mg·L−1) in the OFL degradation rate by functional flora obtained by gradient acclimation, and the functional abundance of the microbial community also increased and stabilized with the depth of the domestication process. The most significant changes in membrane transport were observed in the functional abundance of the microbial community, and it was found that itaconic acid, Tween 80, and L-aspartic acid could increase the biomass of the microbial community under OFL stress. Conclusion Significant changes in the bacterial composition and functional abundance of the microbial community resulted from the addition of amino acid carbon sources, together with the OFL concentration. Functional flora resulting from domestication were better able to degrade OFL. The addition of a co-metabolic carbon source significantly enhanced the biomass of the functional flora. In this study, co-metabolism was performed by adding specific carbon sources, thus achieving metabolic diversity of functional flora and ultimately efficient biodegradation of OFL. This was an important discovery in the field of microbial remediation of environmental contamination.