Oligotrophic characteristics and genomic analysis of the Rhodoligotrophos defluvii lm1T isolated from activated sludge

Oligotrophic conditions have important role in the evolution of life and also the study of ecological status and ecological functions of oligotrophic bacteria in such ecosystems. In this study, the oligotrophic characteristics of the experimental strain Rhodoligotrophos defluvii lm1^T (hereinafter referred to as lm1^T) isolated from activated sludge were investigated. The results indicated that lm1^T was able to grow normally in Luria-Bertani (LB) and diluted LB solid agar plates, demonstrating it to be a facultative oligotrophic bacterium. Research about carbon source and genome analysis revealed that lm1^T lacks 6-phosphofructokinase in the glycolysis process, resulting in the inability to convert glucose-6-phosphate to fructose-6-phosphate, which prevented lm1^T from utilizing glucose. And in line with that, lm1^T can utilize 1,6-diphosphofructose, acetate, propionate, and butyrate to meet its growth requirements. lm1^T possesses a wide range of nitrogen sources utilization, including NaNO₃, urea, NH₄Cl, (NH₄)₂SO₄, peptone, and yeast extract, enabling its adaptation to various complex environments. Additionally, comparative genomic analysis of lm1^T and the model strain Rhodoligotrophos appendicifer 120-1^T revealed that lm1^T had more genes related to degradation metabolism, which aided its adaptation to complex environments.