Metabolites of Brevibacterium antarcticum strain WN5 promote the growth of tobacco seedlings

Abstract:

[Background] The Brevibacterium antarcticum strain WN5, isolated from tobacco- cultivating soil in Guizhou, possesses ammonia transformation capabilities. However, there are few reports on its efficacy in promoting tobacco growth. [Objective] To investigate the growth-promoting effect of WN5 metabolites on tobacco seedlings. [Methods] We applied the WN5 culture to the tobacco seedlings with two leaves and then determined the agronomic traits, morphological traits and vigor of roots, nitrogen nutrients, and stress resistance of the tobacco seedlings. [Results] Four plant hormones and hormone precursors: 1-aminocyclopropane-1-carboxylic acid, trans zeatin, indole-3-acetic acid, and salicylic acid, were detected in the strain culture. The strain culture was then applied to the matrix of tobacco seedlings, which promoted the shoot growth, increasing the plant height, stem circumference, and fresh weight of the seedlings by 42.74%, 12.91%, and 5.00%, respectively. However, the maximum leaf area and leaf number increased without statistically significance, The chlorophyll content in tobacco seedlings increased by 32.86% compared to the control. Additionally, the strain culture enhanced root growth and vigor, increasing the total area, surface area, average diameter, average length, volume, and vigor of roots by 35.42%, 20.54%, 18.22%, 24.07%, 36.56%, and 29.01%, respectively. The growth-promoting effect of the strain culture was more significant on the roots than on the shoots, as the root-to-shoot ratio was increased by 41.67%. Moreover, the treatment with WN5 enhanced the nutrient absorption and stress resistance of tobacco seedlings. Specifically, the treatment increased the levels of nitrate reductase, catalase, superoxide dismutase, and soluble protein by 32.97%, 36.31%, 16.23%, and 18.50%, respectively. [Conclusion] B.antarcticum WN5 can promote the shoot and root growth, improve the root vigor, enhance the nitrogen absorption, and reduce the oxidative stress of tobacco seedlings by producing plant hormones. This finding suggests that WN5 has great potential for widespread application.