posted on 2024-01-23, 18:39authored bySoniya Rayi, Yanyao Cai, Jennifer L. Greenwich, Clay Fuqua, Joseph P. Gerdt
Polymicrobial biofilms are ubiquitous,
and the complex interspecies
interactions within them are cryptic. We discovered the chemical foundation
of antagonistic interactions in a model dual-species biofilm in which Pseudomonas aeruginosa inhibits the biofilm formation
of Agrobacterium tumefaciens. Three
known siderophores produced by P. aeruginosa (pyoverdine, pyochelin, and dihydroaeruginoic acid) were each capable
of inhibiting biofilm formation. Surprisingly, a mutant that was incapable
of producing these siderophores still secreted an antibiofilm metabolite.
We discovered that this inhibitor was N5-formyl-N5-hydroxy-l-ornithine
(fOHOrn)a precursor in pyoverdine biosynthesis. Unlike the
siderophores, this inhibitor did not appear to function via extracellular
metal sequestration. In addition to this discovery, the compensatory
overproduction of a new biofilm inhibitor illustrates the risk of
pleiotropy in genetic knockout experiments. In total, this work lends
new insight into the chemical nature of dual-species biofilm regulation
and reveals a new naturally produced inhibitor of A. tumefaciens biofilm formation.