Amino acids from root exudates induce Bacillus spore germination to enhance root colonization and plant growth promotion

Strains of Bacillus species, plant growth-promoting rhizobacteria, have been commercialized as biofertilizers; they are ideal for this, because these species form spores that can be stored stably for a long time. However, for these spores to exert their full beneficial effects, they must germinate. The specific germination signals in the rhizosphere, particularly those from plant root exudates, remain largely unknown. Here, we investigated the germination signals from different growth states of cucumber ( Cucumis sativus ) for spores of B. velezensis SQR9 and B. subtilis NCIB 3610. We identified the corresponding germination receptors and compared them biochemically between the Bacillus species. Larger plants better stimulated spore germination. Five amino acids – L-isoleucine, L-ornithine, L-valine, L-serine, and β-alanine – were identified as spore germination signals. Combined application of a mixture of these amino acids with bacterial spores markedly enhanced the cucumber-growth-promoting properties of B. velezensis SQR9. The germination receptor for these amino acids was GerA in both Bacillus spp. Differences in spore germination efficiency between B. subtilis and B. velezensis may be attributable to variations in the GerA ligand-recognition sites. Expression of GerA from B. subtilis NCIB 3610 in B. velezensis SQR9 enhanced the spore germination rate of the latter. Our study highlights the pivotal role of amino acids in regulating spore germination of Bacillus and subsequent plant root colonization, emphasizing their potential to enhance the efficacy of Bacillus -based biofertilizers. Engineering of germination receptors is a promising approach to enhance the spore germination efficiency of biofertilizer strains. Information & Authors Information Version history Copyright This work is licensed under a Non Exclusive No Reuse License.

Authors Metrics & Citations Metrics Article Usage 262views 87downloads Citations Download citation Lili Tao, Xinli Sun, Pascale Beauregard, et al. Amino acids from root exudates induce Bacillus spore germination to enhance root colonization and plant growth promotion. Authorea. 17 January 2025. DOI: https://doi.org/10.22541/au.173709381.18225888/v1 DOI: https://doi.org/10.22541/au.173709381.18225888/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu.