Ammonia-oxidizing archaea and comammox Nitrospira clade B as freeze-thaw resistant nitrifiers in wetland soils

摘要

Wetland ecosystems are hotspots for nitrogen cycling, while the community dynamics of nitrification-driving microbes include ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), complete ammonia oxidizer (comammox) Nitrospira, and nitrite-oxidizing bacteria were not well-studied. In this study, we inves-tigated the nitrification process in typical inland and coastal wetlands in northern China and found a high di-versity of ammonia oxidizers. To simulate the freezing-thawing state under natural environment, the soil samples were first frozen at-20 degrees C for two months, and then gradually thawed at 4 degrees C. Further microcosm incubation combined with 13C-DNA-stable isotope probing analyses showed that after the freeze-thaw cycle, only the ac-tivities of AOA and comammox Nitrospira clade B recovered. The results indicated that these two groups of ni-trifiers were more freeze-thaw resistant, which is in line with literature showing that AOA and comammox Nitrospira clade B were relatively more abundant than their counterparts in low-temperature environments. We tested, for the first time, the cold-shock resilience of nitrifying microbes in wetland soils and spotted candidates driving nitrification under fluctuating temperatures.

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