Lipopolysaccharide precursor mutants disrupt unipolar polysaccharide adhesin synthesis and cell surface functions in Agrobacterium tumefaciens.

Mutations in dTDP-l-rhamnose biosynthesis genes rfbA and rfbD in Agrobacterium tumefaciens specifically disrupt UPP GalN synthesis and cause broad cell-surface defects, including impaired motility.

• Why it matters: Surface attachment and motility underpin biofilm formation, but how precursor pools for polysaccharide adhesins connect to outer-membrane integrity and movement is not well defined.
• What they did: A transposon screen identified rfbA and rfbD as linked to UPP GalN biosynthesis; independent deletions were tested for UPP production, attachment/aggregation, and flagellar motility, including suppressor analysis of rescued phenotypes.
• The result: All rfb mutants showed UPP GalN-specific defects plus general attachment and UPP-mediated aggregation defects, and rfbD suppressors disrupted additional rfb genes, exoC, and a putative glycosyl transferase, while dTDP-l-rhamnose single deletions increased outer-membrane stress responses and antibiotic sensitivity.

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