Browsing by Person "Issifu, Sulemana"

Now showing 1 - 2 of 2

Metabolome fingerprinting reveals the presence of multiple nitrification inhibitors in biomass and root exudates of Thinopyrum intermedium
(2024) Issifu, Sulemana; Acharya, Prashamsha; Schöne, Jochen; Kaur-Bhambra, Jasmeet; Gubry-Rangin, Cecile; Rasche, Frank
Biological Nitrification Inhibition (BNI) encompasses primarily NH4 +-induced release of secondary metabolites to impede the rhizospheric nitrifying microbes from per- forming nitrification. The intermediate wheatgrass Thinopyrum intermedium (Kernza®) is known for exuding several nitrification inhibition traits, but its BNI potential has not yet been identified. We hypothesized Kernza® to evince BNI potential through the presence and release of multiple BNI metabolites. The presence of BNI metabolites in the biomass of Kernza® and annual winter wheat (Triticum aestivum) and in the root exudates of hydroponically grown Kernza®, were fingerprinted using HPLC-DAD and GC–MS/MS analyses. Growth bioassays involving ammonia-oxidizing bacteria (AOB) and archaea (AOA) strains were conducted to assess the influence of the crude root metabolome of Kernza® and selected metabolites on nitrification. In most instances, significant concentrations of various metabolites with BNI potential were observed in the leaf and root biomass of Kernza® compared to annual winter wheat. Furthermore, NH4 + nutrition triggered the exudation of various phenolic BNI metabolites. Crude root exudates of Kernza® inhibited multiple AOB strains and completely inhibited N. viennensis. Vanillic acid, caffeic acid, vanillin, and phenylalanine suppressed the growth of all AOB and AOA strains tested, and reduced soil nitrification, while syringic acid and 2,6-dihydroxybenzoic acid were ineffective. We demonstrated the considerable role of the Kernza® metabolome in suppressing nitrification through active exudation of multiple nitrification inhibitors.
Unveiling the plant-associated microbiome responses and nitrification inhibition aspects of perennial intermediate wheatgrass (Thinopyrum intermedium)
(2025) Issifu, Sulemana; Rasche, Frank
Perennialization of agriculture has recently garnered attention as a nature-based solution (NBS) to complement predominantly annual cropping systems, offering a pathway toward sustainable agriculture and enhanced protection of agroecosystems. In this regard, the perennial intermediate wheatgrass, Thinopyrum intermedium, trade name Kernza®, has been proposed as a model plant for achieving perennialization of cereal cropping systems. Kernza® provides a broad range of ecosystem services, including enhanced carbon sequestration, enhanced biodiversity, and regulation of the nitrogen (N) cycle. Some studies reported regulated nitrification in Kernza® fields through reduced N2O emissions, low N leaching, and high legacy N. These traits indicate a plant-exerted control of nitrification through the secretion of bioactive metabolites, a concept known as biological nitrification inhibition (BNI). However, no study had investigated the mechanism behind these BNI traits of Kernza®. Relatedly, existing BNI studies have largely been confined to the identification and testing of single and novel metabolites. Moreover, while some studies have reported the ability of Kernza® to stimulate microbial activity and enhance microbial diversity, there is currently no study in a European context on the potential influence of Kernza® on the rhizosphere microbiome. Thus, this doctoral study aimed to fill these knowledge gaps. The first study used a metabolome fingerprinting approach to profile the metabolome of the Kernza® biomass collected from the field and root exudates collected under N sources (ammonium (NH4+) versus nitrate (NO3-)) in a hydroponic system. Multiple nitrification inhibitors, including several phenolic metabolites, were identified in higher quantities in the biomass of Kernza® than in annual wheat. These metabolites were also concurrently exuded in higher quantities by the roots of Kernza® under NH4+-N source than NO3--N source. Bioassays involving multiple ammonia-oxidising bacteria and archaea (AOB and AOA) confirmed the antimicrobial properties of crude root exudates of Kernza®, as well as individual metabolites such as caffeic acid, vanillic acid, vanillin, and phenylalanine. Soil incubation experiments further demonstrated the nitrification inhibition potential of all tested metabolites, except phenylalanine. This study presents the initial evidence elucidating the mechanisms by which Kernza® regulates nitrification and clarifies the function of Kernza’s® metabolome in mediating nitrification inhibition. In the second study, a pairwise combinatorial approach was employed to assess the interactions among biochemically distinct metabolites co-exuded by Kernza® – caffeic acid, vanillic acid, vanillin, and phenylalanine – against multiple ammonia-oxidisers and soil nitrification. It was found that the metabolites interacted both synergistically and antagonistically against the test strains and soil nitrification, with antagonism being the most predominant interaction among the metabolites. Caffeic acid exhibited single agent dominance (SAD), dominating all other metabolites in all combinations. Furthermore, nitrifiers responded differentially to the metabolites – affirming that nitrifiers are differentially sensitive to inhibitors. Both individual and paired metabolites inhibited the growth of multiple AOB and AOA, as well as soil nitrification – suggesting that both synergism and antagonism did not impair the inhibitory potentials of the metabolites. This evidence suggests that biochemically distinct metabolites exuded by Kernza® and other BNI-positive plants may be interacting in diverse ways in the rhizosphere to suppress nitrification. The third study assessed the impact of Kernza®-induced perennialization on rhizomicrobiome and root endophytes in comparison to annual wheat under an agroclimatic gradient (Sweden, France, and Belgium). The results suggest pronounced similarities in the rhizobacterial composition of Kernza® and annual wheat, with no significant difference in the alpha diversity of their rhizomicrobiome. Beta diversity analysis revealed that factors such as country (agroclimatic conditions), sampling depth (spatial), and year (temporal) rather exerted greater influence than crop type. Notwithstanding, Kernza® promoted the stability of the rhizomicrobiome than annual wheat based on year-on-year comparison – suggesting that perennialization has the ability to protect rhizomicrobiome from ecological perturbation. Moreover, Kernza® recruited and internalised a higher proportion of the rhizosphere microbiome into its root tissues compared to annual wheat, indicating a potential role of crop-associated microbiomes in the lifecycle of Kernza®. Furthermore, an environment-wide comparison with agroecologically relevant database revealed that Kernza®, compared to annual wheat, harboured a significant proportion of rhizobacterial taxa associated with the rhizosphere and grassland ecosystems – supporting the notion that Kernza® shares ecological characteristics with natural grasslands. This study adds to the growing body of knowledge on the rhizosphere ecology of Kernza® and provides further evidence for the ecosystem service potential of Kernza®.