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Poster

Session: Session 2 Presenting Authors at Posters (Evens)

P-346 - Identifying free-living diazotrophs from maize root rhizosphere

Thursday, July 17, 2025
13:30 - 15:15  
Location: Confex Hall 3
Plant microbiota functions and intermicrobial interactions

    Presenting Author(s)

  • SA

    Spencer Arnesen

    Donald Danforth Plant Science Center
    St Louis, Missouri, United States

    • Author(s)

  • WR

    Will Ranney

    Donald Danforth Plant Science Center
    St Louis, Missouri, United States

  • FG

    Felix Guo

    Donald Danforth Plant Science Center
    St Louis, Missouri, United States

  • JS

    Josh Sumner

    Donald Danforth Plant Science Center
    St Louis, Missouri, United States

  • RB

    Rebecca Bart

    Donald Danforth Plant Science Center
    St. Louis, Missouri, United States

Nitrogen-fixing bacteria (diazotrophs) can provide plants with a significant portion of their nitrogen needs. Therefore, the identification, isolation, and use of free-living diazotrophs found in the rhizospheres of common non-leguminous crops represents a promising avenue toward decreasing synthetic fertilizer use and its associated negative effects. The nifH gene, part of the nitrogenase enzyme, is a common marker used to identify potential diazotrophs. We investigated nifH abundance across a field planted with maize and evaluated nifH gene diversity in rhizosphere-associated diazotrophs. Using four distinct nifH PCR primer pairs, we assessed nifH presence in 200 bacterial isolates cultured from the maize rhizosphere on nitrogen-free media. NifH was detected by different PCR primers in a genus-specific manner, indicating genus-specific nifH sequence variability. Furthermore, by PCR, less than 10% of isolates were nifH+, suggesting nifH sequence variability in the rhizosphere may be too diverse to assess through PCR approaches. To address this limitation, we turned to whole-genome sequencing of potential diazotrophs to gain a thorough assessment of nifH presence and sequence variability. Our current findings highlight the extensive nifH diversity in the maize rhizosphere, underscore the limitations of PCR-based identification of free-living diazotrophs, and indicate the need for whole-genome approaches to capture the full range of nifH variants in rhizosphere diazotrophs.