Mechanisms for Generating Low Potential Electrons across the Metabolic Diversity of Nitrogen-Fixing Bacteria.

The availability of fixed nitrogen is a limiting factor in the net primary production of all ecosystems. Diazotrophs overcome this limit through the conversion of atmospheric dinitrogen to ammonia. Diazotrophs are phylogenetically diverse bacteria and archaea that exhibit a wide range of lifestyles and metabolisms, including obligate anaerobes and aerobes that generate energy through heterotrophic or autotrophic metabolisms.

Rnf and Fix Have Specific Roles during Aerobic Nitrogen Fixation in Azotobacter vinelandii.

Biological nitrogen fixation requires large amounts of energy in the form of ATP and low potential electrons to overcome the high activation barrier for cleavage of the dinitrogen triple bond. The model aerobic nitrogen-fixing bacteria, Azotobacter vinelandii, generates low potential electrons in the form of reduced ferredoxin (Fd) and flavodoxin (Fld) using two distinct mechanisms via the enzyme complexes Rnf and Fix. Both Rnf and Fix are expressed during nitrogen fixation, but deleting either or genes has little effect on diazotrophic growth.

Low-risk meningioma: Initial outcomes from NRG Oncology/RTOG 0539.

Background: Three- and five-year progression-free survival (PFS) for low-risk meningioma managed with surgery and observation reportedly exceeds 90%. Herewith we summarize outcomes for low-risk meningioma patients enrolled on NRG/RTOG 0539.

Methods: This phase II trial allocated patients to one of three groups per World Health Organization grade, recurrence status, and resection extent.