AUTHOR=Nshimiyimana Jean Bosco , Zhao Kang , Wang Wenying , Kong Weidong 

TITLE=Diazotrophic abundance and community structure associated with three meadow plants on the Qinghai-Tibet Plateau

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1292860

DOI=10.3389/fmicb.2023.1292860

ISSN=1664-302X

ABSTRACT=<p>Symbiotic diazotrophs form associations with legumes and substantially fix nitrogen into soils. However, grasslands on the Qinghai-Tibet Plateau are dominated by non-legume plants, such as <italic>Kobresia tibetica</italic>. Herein, we investigated the diazotrophic abundance, composition, and community structure in the soils and roots of three plants, non-legume <italic>K. tibetica</italic> and <italic>Kobresia humilis</italic> and the legume <italic>Oxytropis ochrocephala</italic>, using molecular methods targeting <italic>nifH</italic> gene. Diazotrophs were abundantly observed in both bulk and rhizosphere soils, as well as in roots of all three plants, but their abundance varied with plant type and soil. In both bulk and rhizosphere soils, <italic>K. tibetica</italic> showed the highest diazotroph abundance, whereas <italic>K. humilis</italic> had the lowest. In roots, <italic>O. ochrocephala</italic> and <italic>K. humilis</italic> showed the highest and the lowest diazotroph abundance, respectively. The bulk and rhizosphere soils exhibited similar diazotrophic community structure in both <italic>O. ochrocephala</italic> and <italic>K. tibetica</italic>, but were substantially distinct from the roots in both plants. Interestingly, the root diazotrophic community structures in legume <italic>O. ochrocephala</italic> and non-legume <italic>K. tibetica</italic> were similar. Diazotrophs in bulk and rhizosphere soils were more diverse than those in the roots of three plants. Rhizosphere soils of <italic>K. humilis</italic> were dominated by Actinobacteria, while rhizosphere soils and roots of <italic>K. tibetica</italic> were dominated by Verrumicrobia and Proteobacteria. The <italic>O. ochrocephala</italic> root diazotrophs were dominated by Alphaproteobacteria. These findings indicate that free-living diazotrophs abundantly and diversely occur in grassland soils dominated by non-legume plants, suggesting that these diazotrophs may play important roles in fixing nitrogen into soils on the plateau.</p>