Available online 14 August 2022, 102626

Levels of pollutants are several folds higher than the maximum permissible limit.

Cultivated 200 ecologically significant strains with 12 potential novel taxa.

Out of 12 novel taxa, six-show low similarity and first time reported from leachate.

Archaea constitutes 30–50% part of leachate microbial communities.

Methanogens and Haloarachaea prevail in the leachate microbial community.

The landfill is a convenient and affordable method of municipal solid waste (MSW) management. Landfill leachate contains a heavy load of pollutants and pathogens. Discharge of untreated leachate is the leading cause of surface and groundwater contamination and a threat to public and environmental health. To develop an efficient leachate treatment technology, an in-depth understanding of landfill chemistry and microbiology is essential. In the present manuscript, we conducted a comparative study of three different landfill leachate samples using cultivation-based and culture-independent molecular studies. We cultivated 85 species of aerobic, anaerobic bacteria and archaea from leachate represented by a total of 200 strains using extensive culturomics approaches. Twelve out of 200 cultivated strains of bacteria showed very low 16S rRNA gene sequence similarity (84–98.6%) with their closest relatives and could be the potential novel taxa, the first time cultivated from leachate. Members of the six genera only have 2–5 representatives from past studies from other habitats but first time cultivated from leachate. In addition to bacteria, we also cultivated and characterized different groups of methanogenic archaea. Our chemistry data indicate that leachate is a highly stressed ecosystem with an assemblage of many toxic wastes like sulfur, zinc, mercury, chromium, etc. 16S rRNA gene-based amplicon analysis showed the dominance of (30–55%) methanogens and haloarachaea. Our data suggest that archaea are the significant regulators of leachate ecology, and more in-depth studies with multiple leachate samples are required to understand their role in leachate nutrient cycling and the development of effective leachate treatment technology.

Landfill

Leachate

Obligate anaerobes

Methanogens

Haloarchaea

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