“…Despite these information, little is known about the microbial eukaryotic communities and metabolic potentials in the deeper seawaters (8,727–11,000 m) of the Mariana Trench, where unique microbial populations (e.g., increased amount of SAR406, hydrocarbon-degrading microbes) have been observed ( Ichino et al, 2015 ; Nunoura et al, 2015 ; Liu et al, 2018 , 2019b ; Gao et al, 2019 ). In addition, whether microbial eukaryotes exhibit unique high-pressure adaptation mechanisms as found in bacteria and archaea in our previous studies ( Zheng et al, 2020 ; Zhong et al, 2020 ) is still unknown. Thus, knowledge of microbial eukaryotes at the bottom of the Mariana Trench, the deepest ocean part on Earth, is necessary for a better understanding of their ecological roles and potential adaptability.…”