Investigation of diverse bacterial communities in the leachate from pig decomposition by using high-throughput sequencing
The leachate generated by the decomposition of animal carcass has been implicated as an environmental contaminant around the burial site. The organic degradation of carcass by environmental factors including microbes generates a leachate, and this product may affect the other soil microorganisms and environmental characters. Therefore, this study was conducted to investigate the microbial communities in leachate originated from pig carcass decomposition by using high-throughput sequencing. The leachate samples were collected once per week during 98 days, and the microbial communities in the leachate were investigated for 14 weeks by 16S rRNA gene analysis. A total of 51,230 reads were obtained from extracted DNA of 6 different samples (1, 2, 3, 4, 6 and 14 weeks), phylum of Firmicutes was predominated induring sampling periods. The diversity of bacterial community in leachate was the highest at 6 weeks, whereas the diversity of communities in 2 weeks and 14 weeks were lower than other samples. The relative abundance of Firmicutes was reduced, while the proportions of Bacteroidetes and Proteobacteria were increased from 3 weeks to 6 weeks. The composition of community was seem to be returned after 14 weeks at phylum level, however, the difference of community structure between the samples of 14 weeks and early stage (1-2 weeks) could be investigated clearly at family, genus and species level. The pH of lechate could be related to the shift of microbial community. Most of the bacteria were anaerobic bacteria belonging to the families of Tissierella, Clostridiales and Peptostreptococcus. The genus of Peptostreptococcus was increased at 14 weeks sample, uncultured Tissierella was increased from 2 weeks to 4 weeks samples. The changes of bacterial community were also investigated by PCoA plots using UniFrac distance and community similarity analysis. These results indicated that the bacterial communities in leachate generated from pig decomposition were continuously shifted during the period of decomposition and this change could be influenced to burial sites.