Genome-wide interrogation of genetic requirements for root colonization by CRISPRi-seq in Bacillus subtilis

Bacillus subtilis, a beneficial plant growth promoting rhizobacterium, has been found to enhance root colonization by Arabidopsis thaliana, though the genetic mechanisms underlying this process have been unclear. To elucidate these mechanisms, researchers utilized genome-wide CRISPR interference sequencing (CRISPRi-seq) to systematically identify genes essential for early root colonization by the B. subtilis strain 3610.

The study employed an inducible CRISPRi library to screen for bacterial fitness during hydroponic root colonization, while complementary RNA-seq provided insights into the transcriptional state of root-associated cells under the same conditions.

The investigation identified 249 genes that impact root colonization. A key finding revealed a crucial role of cell envelope remodeling during early root association, specifically in wall teichoic acid synthesis and D-alanylation processes. Additionally, the study uncovered a metabolic shift towards TCA-cycle-driven aerobic growth, with the uptake of fructose, and the active repression of sporulation, competence, and prophage programs. The researchers also observed an induction of secondary metabolite biosynthesis.

This comprehensive analysis establishes CRISPRi-seq as a powerful tool for dissecting bacterial-plant interactions, particularly those relevant to sustainable agriculture practices.