4.4. Bathyarchaeia co-occurred with methanogens and ammonia
oxidizers
Genomic analysis suggested that Bathyarchaeia may play a crucial
role in global carbon and nitrogen cycling (Zhou et al. 2018). In this
study, we found the interactions between Bathyarchaeia and other
archaea were very complex, and Bathyarchaeia play an important
role in the construction of the archaeal network (Fig. 5a). The
co-occurrences of Bathyarchaeia and acetate methanogens,
including Methanosarcinia and Methanobacteria , were also
found in other environmental habitats. These results suggest thatBathyarchaeia can be involved in carbon cycling by producing
acetate for the heterotrophic microbes and acetoclastic methanogens, and
acetate might be the bridge associating the interactions betweenBathyarchaeia and Methanosarcinia (Xiang et al. 2017; Zou
et al. 2020). The co-occurrences of Bathyarchaeia and hydrogen
Methanogens were also found in paddy soils in this study. These results
suggested that Bathyarchaeia might be involved in carbon cycling
differently and play a crucial role in the carbon cycle in arable soils.
Bathyarchaeia also frequently co-occurred with members ofNitrososphaeria (Fig. 5d), which is consistent with the results
of the global meta-analysis (Xue et al. 2023). Nitrososphaeria is
a group of ammonia-oxidizing archaea highly abundant in rice rhizosphere
soil with fertilization (Tang et al. 2019). Ammonia oxidizing archaea
plays an important role in the soil nitrogen cycle, catalyzing the first
step of the ammonia oxidation process (Baker et al. 2020). Genomic
studies suggest that Bathyarchaeia may be involved in the
nitrogen cycle, and genes involved in ammonia and urea production were
found in Bathyarchaeial MAGs (Pan et al. 2020). Thus,Bathyarchaeia was suggested as a transfer station for nitrogen
compounds in the global nitrogen cycle (Pan et al. 2020). Additionally,
the metagenomic analysis showed that Nitrososphaeraceae contain
genes involved in urea degradation, indicating that Bathyarchaeiamay interact with Nitrososphaeraceae via urea production and
transformation (Wu et al. 2021). Agricultural systems depend on
significant nitrogen fertilizer inputs for farm yield; therefore, the
role of Bathyarchaeia in agricultural soils on the nitrogen cycle
warrants further research.
We also found that Bathyarchaeia indicated higher niche overlap
with other archaea than other archaea. Higher overlap means higher
association with other microorganisms, whereas no higher competition was
found in paddy soils. This view is supported by network analysis thatBathyarchaeia plays a crucial role in the structure of a network
(de Boer & Prins 1990; Holt 1987). In the future, more research is
needed to investigate the ecological function of Bathyarchaeia in
paddy soils.