Exploring native arsenic (As)-resistant bacteria: unveiling multifaceted mechanisms for plant growth promotion under As stress.

Aims: This study explores the plant growth-promoting effect (PGPE) and potential mechanisms of the arsenic (As)-resistant bacterium Flavobacterium sp. A9 (A9 hereafter).

Methods and results: The influences of A9 on the growth of Arabidopsis thaliana, lettuce, and Brassica napus under As(V) stress were investigated. Additionally, a metabolome analysis was conducted to unravel the underlying mechanisms that facilitate PGPE. Results revealed that A9 significantly enhanced the fresh weight of Arabidopsis seedlings by 62.6%-135.4% under As(V) stress. A9 significantly increased root length (19.4%), phosphorus (25.28%), chlorophyll content (59%), pod number (24.42%), and weight (18.88%), while decreasing As content (48.33%, P ≤ .05) and oxidative stress of Arabidopsis. It also significantly promoted the growth of lettuce and B. napus under As(V) stress. A9 demonstrated the capability to produce ≥31 beneficial substances contributing to plant growth promotion (e.g. gibberellic acid), stress tolerance (e.g. thiamine), and reduced As accumulation (e.g. siderophores).

Conclusions: A9 significantly promoted the plant growth under As stress and decreased As accumulation by decreasing oxidative stress and releasing beneficial compounds.