Phagotrophic protists can change microbial nitrogen conversion patterns during swine manure composting

Protists are important microorganisms involved in the transformation of nutrients, but little information is available regarding their roles in composting. This study investigated the changes in the protist community during composting and their relationships with the conversion of nitrogen. The protist community structure varied among the different composting phases, but the communities were similar in the cooling phase and at the end of the thermophilic phase. Phagotrophic protists such as Acantharea-Group-II_XX and Acantharea_XXX dominated in the composting process. The abundance of Acantharea-Group-II_XX increased by 12.8% in the thermophilic phase, whereas that of Acantharea_XXX increased by 74.5% and 275.3% during the cooling and maturation phases, respectively. The protist community was mainly affected by the NO3- and NO2- concentrations and the bacterial community, where NO3- and NO2- inhibited phagotrophic protists. Furthermore, compared with the nitrifying bacterial communities, the denitrifying bacterial communities were more conducive to the growth of Acantharea-Group-II_XX and Acantharea_XXX. Phagotrophic protists were key predators that regulated bacteria with denitrification functions.

Automated summary

This study investigated the changes in the protist community during composting and found that phagotrophic protists play a significant role in the composting process. The protist community structure varied among different phases, and it was influenced by NO3- and NO2- concentrations as well as the bacterial community.