Atmospheric CO₂ fixation by microbial autotrophs presents a sustainable alternative to energy-intensive chemical processes, offering significant potential for biotechnological applications. However, understanding the genetic diversity, evolutionary adaptations, and metabolic capabilities of autotrophic carbon-fixing lineages (ACL) requires a comparative genomic approach. This study employs pangenome analysis to systematically assess the core, accessory, and unique genetic components across diverse ACL bacteria, with a particular focus on the recently revised genus Xanthobacter and the newly proposed Roseixanthobacter. By integrating phylogenetic, functional, and metabolic insights, we aim to elucidate conserved and variable genetic traits that contribute to CO₂ fixation efficiency and industrial relevance. A total of 546 high-quality genomes spanning 121 ACL microbial species were selected for analysis, following rigorous genome quality control measures based on CheckM contamination thresholds, contig limits, and genome size variation criteria. Initial phylogenomic analyses identified 16 microbial genera closely related to Xanthobacter, including Ancylobacter, Azorhizobium, Cupriavidus, Hydrogenophaga, Moorella, and Synechococcus, among others. Genomes were uniformly re-annotated to ensure consistency in gene identification. Pangenome reconstruction, core-genome diversity assessments, orthologous group clustering, and essential metabolic pathway mapping were performed to identify key functional traits enabling inorganic carbon assimilation, H₂ utilization, and N₂ fixation. Among these traits are RuBisCO for CO₂ fixation, hydrogenases for H₂ metabolism, and nitrogenase complexes for converting atmospheric N₂ into bioavailable forms. The findings of this study would contribute to metabolic engineering efforts, facilitating the development of optimized microbial strains for sustainable biotechnology applications such as alternative protein production, biofuel production, carbon sequestration, and synthetic biology efforts.