Soil comammox Nitrospira dominates over ammonia-oxidizing archaea and bacteria in the invasion of Solidago canadensis

Abstract

Background

Invasive plants often positively interact with nitrogen cycle microorganisms, but the key response species of nitrification community to plant invasion remain poorly understood. Additionally, the recent finding of complete ammonia oxidizing (comammox) bacterium Nitrospira has caused a heated debate on the relative importance of ammonia oxidizing bacteria (AOB), archaea (AOA) and comammox Nitrospira in environments.

Methods

We conducted a field study to explore the effect of the exotic plant Solidago canadensis invading the habitat of the native plant Humulus scandens on the soil communities of AOB, AOA and comammox Nitrospira in eastern China. The invasions were classified to low, medium and high levels (S. canadensis < 10%, ~ 50%, and > 90%, respectively).

Results

We found that comammox Nitrospira existed in all samples (0.36 to 1.33 × 10⁷ copies g⁻¹ DW soil, n = 3), dominating over both AOB (0.29 to 8.52 × 10⁶ copies g⁻¹ DW soil) and AOA (0.38 to 1.74 × 10⁵ copies g⁻¹ DW soil) by 1–2 orders of magnitude. S. canadensis invasion decreased the abundance of AOB and AOA (p < 0.05) but increased the abundance of comammox Nitrospira in S. canadensis rhizosphere. All comammox Nitrospira detected in this study fall into Clade A rather than Clade B. S. canadensis invasion decreased the diversity of comammox Nitrospira (p < 0.05). Importantly, S. canadensis invasion changed the community structure of comammox Nitrospira in plant rhizospheres.

Conclusion

Our study suggests that comammox Nitrospira might be a crucial and beneficial N-cycler bacterium in S. canadensis invasion process. 

Graphical Abstract