Secondary metabolites of fluorescent pseudomonads
Bacteria belonging to the genus Pseudomonas have the astonishing ability to adapt to different environments and to interact with different host organisms. We would like to learn more about the ways by which these bacteria communicate with each other and with their hosts, and to find out about some fundamental regulatory mechanisms that govern this adaptability.
In the Gram-negative bacterium Pseudomonas aeruginosa iron is acquired with two siderophores, pyoverdine and pyochelin, which both contribute to the virulence of this opportunistic human pathogen. Our lab has been interested in the biosynthesis of pyochelin for several years. We have cloned the genes which are needed for pyochelin formation and we have contributed to the understanding of the biosynthetic pathway. Recently, we discovered that some strains of Pseudomonas fluorescens make enantio-pyochelin, the optical antipode of the P. aeruginosa siderophore. Our current work focuses on the biosynthesis of enantio-pyochelin and on the regulatory mechanisms governing pyochelin- and enantio-pyochelin-mediated iron uptake.
L-2-amino-4-methoxy-trans-3-butenoic acid (AMB) is one of many secondary metabolites and exoproducts made by Pseudomonas aeruginosa which allow this opportunistic pathogen to compete in the environment and to cause infections in humans, insects, nematodes, plants and amoebae. Like other y-substituted vinylglycines, AMB inhibits pyridoxal phosphate-dependent enzymes which are primarily involved in the biosynthesis of amino acids and amino acid-derived metabolites. We recently identified a five-gene cluster specifying AMB biosynthesis in P. aeruginosa. Two of these genes encode non-ribosomal peptide synthétases, suggesting that AMB biosynthesis occurs by a thiotemplate mechanism. The long-term goal of our research is to understand how, when and for what purpose AMB is made, and how P. aeruginosa escapes AMB toxicity.