Metagenomic Analysis of the Microbial Diversity in Solid Waste from Okhla Landfill, New Delhi, India

Bacterial Community Structure and Predicted Metabolic Function of Landfilled Municipal Solid Waste in China

The biodegradation behavior of municipal solid waste (MSW) depends on the diversity and metabolic function of bacterial communities, which are affected by environmental factors. However, the diversity of the bacterial communities and metabolic functions in MSW, as well as their influencing factors, remain unclear. In deep-aged MSW, the abovementioned deficiencies are more significant, and will effectively hamper landfill disposal. In this study, high-throughput sequencing was performed to examine the bacterial community structure and metabolic function from depths of 10 m to 40 m, of two large MSW landfills on the southeast coast of China. Thermotogota (1.6–32.0%), Firmicutes (44.2–77.1%), and Bacteroidota (4.0–34.3%) were the three dominant phyla among the 39 bacterial phyla identified in aged MSW samples. Bacterial genera associated with the degradation of many macromolecules, e.g., Defluviitoga, Hydrogenispora, and Lentimicrobium were abundantly detected in MSW samples, even in aged MSW. Redundancy analysis (RDA) showed that bacterial diversity in the landfills was most strongly correlated with electrical conductivity, age, and moisture content of the MSW. Tax4fun2 analysis predicted that there were abundant metabolism functions in aged MSW, especially functional enzymes (e.g., glycine dehydrogenase and cellulase) related to amino acids and cellulose degradation. This study increases our understanding of the bacterial diversity and functional characteristics in landfilled MSW.

Analysis of Microbial Communities in Aged Refuse Based on 16S Sequencing

Aged refuse is widely considered to have certain soil fertility. 16S rRNA amplicon sequencing is used to investigate the microbial community of aged refuse. The aged refuse is found to contain higher soil fertility elements (total nitrogen, total phosphorus, total potassium, etc.) and higher concentrations of heavy metals (Pb, Cd, Zn, and Hg). Taxonomy based on operational taxonomic units (OTUs) shows that Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria, and Gemmatimonadetes are the main bacterial phyla in the two soils and there is a palpable difference in the microbial community composition between the two groups of samples. The genera Paramaledivibacter, Limnochorda, Marinobacter, Pseudaminobacter, Kocuria, Bdellovibrio, Halomonas, Gillisia, and Membranicola are enriched in the aged refuse. Functional predictive analysis shows that both the control soil and aged refuse have a high abundance of “carbohydrate metabolism” and “amino acid metabolism”, and show differences in the abundance of several metabolism pathways, such as “xenobiotics biodegradation and metabolism” and “lipid metabolism”. Aged refuse and undisturbed soil show significant differences in alpha diversity and microbial community composition. Multiple environmental factors (Hg, TN, Cr, Cd, etc.) significantly impact microorganisms’ abundance (Marinobacter, Halomonas, Blastococcus, etc.). Our study provides valuable knowledge for the ecological restoration of closed landfills.