Phosphorus limitation's biochemical process that hinders nitrogen fixation in the diazotrophic bacteria Klebsiella variicola W12

Abstract

In both natural and agricultural environments, biological nitrogen (N) fixation (BNF) is essential to the supply of nitrogen. Using BNF may significantly reduce agroecosystems' reliance on chemical fertilizers, which can support sustainable agriculture. Although the underlying process is unclear, many field investigations have shown that BNF may be significantly inhibited in phosphorus (P)-deficient conditions.Supplies and Procedures: In order to understand how P availability impacts N fixing, comparative proteomics and lipidomics analyzes were performed on a diazotrophic bacteria, Klebsiella variicola W12, under P-deficient and P-replete circumstances.Results: K. variicola W12's N fixing activity was significantly suppressed under P deficit. The bacteria replaced glycerophospholipids in its membrane with P-free ornithine lipids in response to P constraint, lowering the cellular need for P. Comparative proteomics revealed that whereas nitrogenase and N-fixation-related transcriptional regulators NifL and NifA were downregulated, P restriction led to the overexpression of the PhoBR two-component system and a variety of organic and inorganic P uptake and transport systems.Conclusion: These findings offered molecular proof of how P availability controls BNF and demonstrated lipid remodeling as an adaptation mechanism for N2-fixing bacteria to thrive under P stress. Thus, a conceptual model of N–P interaction at the level of microbial metabolism is put forward. Our research emphasizes the significance of controlling P availability to optimize the potential of BNF in agroecosystems for agricultural sustainable production and offers a simple yet tenable explanation for how P insufficiency reduces BNF seen in the field.