Plant Growth Promotion Diversity in Switchgrass-Colonizing, Diazotrophic Endophytes

Abstract

Endophytic nitrogen-fixing (diazotrophic) bacteria are essential members of the microbiome of switchgrass (Panicum virgatum), considered to be an important commodity crop in bioenergy production. While endophytic diazotrophs are known to provide fixed atmospheric nitrogen to their host plant, there are many other plant growth-promoting (PGP) capabilities of these organisms to be demonstrated. The diversity of PGP traits across different taxa of switchgrass-colonizing endophytes is understudied, yet critical for understanding endophytic function and improving cultivation methods of important commodity crops. Here, we present the isolation and characterization of three diazotrophic endophytes: Azospirillum agricola R1C, Klebsiella variicola F10Cl, and Raoultella terrigena R1Gly. Strains R1C and F10Cl were isolated from switchgrass and strain R1Gly, while isolated from tobacco, is demonstrated herein to colonize switchgrass. Each strain exhibited highly diverse genomic and phenotypic PGP capabilities. Strain F10Cl and R1Gly demonstrated the highest functional similarity, suggesting that, while endophyte community structure may vary widely based on host species, differences in functional diversity are not a clearly delineated. The results of this study advance our understanding of diazotrophic endophyte diversity, which will allow us to design robust strategies to improve cultivation methods of many economically important commodity crops.

Interaction analysis of tobacco leaf microbial community structure and volatiles flavor compounds during cigar stacking fermentation

“…Within strong salt tolerance, they could better adapt to the alkaline environment of CTLs, and had the effects of promoting growth, resistance to diseases and pests, and pollutant degradation. They had great economic value and application development potential ( Li et al, 2019 ; Gushgari-Doyle et al, 2021 ; Gibot-Leclerc et al, 2022 ).…”

Plant quercetin degradation by gut bacterium Raoultella terrigena of ghost moth Thitarodes xiaojinensis

“…R. terrigena is considered to be an environmental bacterium, which is isolated mainly from soil and aquatic environments ( Fazal et al, 2019 ). It is also isolated from plant roots of Nicotiana tabacum and switchgrass Panicum virgatum , and considered to be an endophytic nitrogen-fixing bacterium ( Schicklberger et al, 2015 ; Gushgari-Doyle et al, 2021 ). Furthermore, R. terrigena is detected from the gut of Dendroctonus rhizophagus and D. valens , exhibiting high acetylene reduction activity ( Morales-Jimenez et al, 2013 ), as well as from the reproductive system of the female oriental fruit fly Bactrocera dorsalis , and its metabolites are found to be attractive to adults in field trapping assays ( Shi et al, 2012 ).…”

“…An abundance of bacterial and fungal colonies was observed on the medium with unsterilized seeds, but no colony was observed on the medium plates with surface-sterilized seeds ( Supplementary Figure S1 ). The bud and root tissues from surface sterilized seeds were then macerated and used as inoculum on plates containing modified Jensen’s medium ( Gushgari-Doyle et al, 2021 ) and LB medium. Distinct colonies were purified by streaking on LB plates and identified as described above.…”