Identification of Aniline-Degrading Bacteria Using Stable Isotope Probing Technology and Prediction of Functional Genes in Aerobic Microcosms

Aniline, a vital component in various chemical industries, is known to be a hazardous persistent organic pollutant that can cause environmental pollution through its manufacturing, processing, and transportation. In this study, the microcosms were established using sediment with a history of aniline pollution as an inoculum to analyze the aniline biodegradation under aerobic conditions through stable isotope probing (SIP) and isopycnic density gradient centrifugation technology. During the degradation assay, aniline that was 13C-labeled in all six carbons was utilized to determine the phylogenetic identity of the aniline-degrading bacterial taxa that incorporate 13C into their DNA. The results revealed that aniline was completely degraded in the microcosm after 45 and 69 h respectively. The bacteria affiliated with Acinetobacter (up to 34.6 +/- 6.0%), Zoogloea (up to 15.8 +/- 2.2%), Comamonas (up to 2.6 +/- 0.1%), and Hydrogenophaga (up to 5.1 +/- 0.6%) genera, which are known to degrade aniline, were enriched in the heavy fractions (the DNA buoyant density was 1.74 mg L-1) of the 13C-aniline treatments. Moreover, some rarely reported aniline-degrading bacteria, such as Prosthecobacter (up to 16.0 +/- 1.6%) and Curvibacter (up to 3.0 +/- 1.6%), were found in the DNA-SIP experiment. Gene families affiliated with atd, tdn, and dan were speculated to be key genes for aniline degradation based on the abundance in functional genes and diversity in different treatments as estimated using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States version 2 (PICRUSt2) and the Kyoto Encyclopedia of Genes and Genomes (KEGG). This study revealed the functional bacteria and possible degradation genes for aniline degradation in simulated polluted environments through SIP. These findings suggest that important degrading bacteria for the transformation of aniline and potential degradation pathways may be useful in the effective application of bioremediation technologies to remediate aniline-contaminated sites.