Chromosome Architecture Impacts Virulence and Competitiveness in Agrobacterium tumefaciens C58

Experiment Description: To elucidate the impact of chromosome architecture on transcription, we generated isogenic Agrobacterium strains that only differ in chromosome configurations. We chose A. fabrum C58 and C58F, to generate a set of four strains with different chromosome configurations: C58 Wildtype (WT, Circular + Linear), C58 Circularized (C58Cir, Circular + Circular), C58F (FL, Linear), and C58F Circularized (FCir, Circular). Samples from each strain were grown in triplicate in two conditions, acetosyringone (AS) and control solvent (DMSO). RNAseq was performed on samples from each condition and gene expression was measured in the AS samples relative to its DMSO control. Article abstract: Chromosome architecture plays a crucial role in bacterial adaptation, yet its direct impact remains unclear. Different bacterial species, and even strains within the same species, exhibit diverse chromosomal configurations, including a single circular or linear chromosome, two circular chromosomes, or a circular-linear combination. To investigate how these architectures shape bacterial behavior, we generated near-isogenic strains representing each configuration in Agrobacterium tumefaciens C58, an important plant pathogen widely used for plant genetic transformation. Strains with a single-chromosome architecture, whether linear or circular, exhibited faster growth, enhanced stress tolerance, and greater inter-strain competitiveness. In contrast, bipartite chromosome strains showed higher virulence gene expression and enhanced transient plant transformation efficiency, suggesting a pathogenic adaptation. Whole transcriptome analysis revealed architecture-dependent gene expression patterns, underscoring the profound impact of chromosome organization on Agrobacterium fitness and virulence. These findings highlight how chromosome structure influences bacterial adaptation and shapes evolutionary trajectories.