Seed endophytic ammonia oxidizing bacteria in transmit to offspring plants and contribute to nitrification in the root zone.

Background: Ammonia oxidizing bacteria (AOB) in soil are of great biological importance as they regulate the cycling of N in agroecosystems. Plants are known to harbor AOB but how they occupy the plant is an unresolved question.

Methods: Metabarcoding studies were carried out using Illumina MiSeq sequencing to test the potential of seed vectored AOB exchange between plants and soil.

Results And Discussion: We found 27 sequences associated with AOB strains belonging to the genera , and inhabiting seeds collected from four geographically distanced alpine meadows. was the most dominant across the four locations. The AOB community in seeds was compared with that of the leaves, roots and soil in one location. Soil and seeds harbored a rich but dissimilar AOB community, and sp. PJA1, sp. Nsp17 and sp. RY3C were present in all plant parts and soils. When seeds were germinated in sterilized growth medium under greenhouse conditions, the AOB in seeds later appeared in leaves, roots and growth medium, and contributed to nitrification. Testing the AOB community of the second-generation seeds confirmed vertical transmission, but low richness was observed.

Conclusion: These results suggest seed vectored AOB may play a critical role in N cycle.