Energy-driven community succession in landfills based on a cross-kingdom abundance quantification method

Landfill provides a unique niche for both prokaryotic and eukaryotic microorganisms, in which organic matter and physiochemical conditions continuously change with the landfill age and drive the succession of landfill microbiomes. Nonetheless, information on the spatiotemporal changes of landfill microbiomes, particularly the prokaryotic and eukaryotic communities and their interactions, remain scarce. In this study, a new cross-kingdom abundance quantification method was devised to obtain cell abundance of both prokaryotes and eukaryotes based on high-throughput sequencing, and employed to elucidate microbiomes of leachate samples collected from nationwide landfills in China. Results showed the clustering of two groups of microbial communities based on their landfill ages (i.e. Group-I, <10 years; Group-II, ?10 years), and 1320.9 and 88.0 times of abundance difference between prokaryotes and eukaryotes in the Group-I and –II communities, respectively. Organic matter-derived reducing equivalent was determined as a primary factor governing the landfill microbial abundance, assembly and interactions. In contrast to the dominance of stable methanogenic digestion populations in Group-I communities, aerobic heterotrophs played a primary role in element cycling in Group-II communities, in which the heterotrophic bacteria and fungi synergistically converted recalcitrant organic matter. Interestingly, protozoa and metazoa as bacteria/fungi predators decreased the stability of Group-II communities in a top-down manner. Based on these observations, a scenario was proposed for the energy-driven succession of landfill microbiomes and mediated biogeochemical processes. Our study provided the first large-scale and comprehensive insight into the landfill microbiomes for their future sustainable management.