Fecha de publicación: 05/01/2023 Fuente: WIPO Rice Methods and systems are provided for generating and utilizing a genetically engineered bacterium comprising a modification in a nifA gene or homolog thereof that can result in a bacterium with modified regulation of nitrogen fixation or assimilation activity. Genetically engineered bacteria with modified nitrogen fixation or assimilation activity are also provided. The genetically engineered bacterium can fix nitrogen in the presence of nitrogen (e.g., ammonium), and/or oxygen.