College of Ocean and Earth Sciences, Xiamen University
Luncheon Seminars #70: How siderophores really work in natural matrices?
2017/5/4 407
2017-05-08 2017-5-8 (星期一) 11:40-13:30(讲座于12:20开始)
Dr. Jean-Philippe Bellenger, Associate Professor
A3-206, Zhou Long Quan Bldg

-       2001-2005, PhD Biogeochemistry, ECPM, CGS, Louis Pasteur University, Strasbourg, France
-       2001, Advanced degree in Soil Science, INRA-ENSAM (National institute of agronomic research), Montpellier & Henri Poincare University, Nancy France.
-       2000, Master’s degree in Cellular Biology and Physiology, Claude Bernard University, Lyon, France
-       1999, Master’s degree in Geosciences, Claude Bernard University, Lyon, France

-       Trace metal and nitrogen biogeochemistry

-       2010 to present, Associate Professor, and Chair holder of the Canadian Research Chair in Terrestrial Biogeochemistry, Chemistry department, Sherbrooke University, Qc, Canada.
-       2005-2010, Research associate, Princeton Environmental Institute, Princeton University, NJ, USA.

Since trace metal bioavailability, while potentially toxic, affects key enzymatic activities, the cycling of metals in the environment can critically impact the cycling of major nutrients such as nitrogen or carbon. For instance, iron (Fe) is the most important metal in biology. Despite its abundance on earth its bioavailability is very low in both terrestrial and marine ecosystems, due to its very low solubility in oxic solution, not greater than 10-18 M at pH 7. To overcome the challenge of Fe acquisition, many microorganisms produce siderophores, low molecular weight ligand with high affinity for Fe, to retrieve Fe from natural sources. Siderophores are released in the environment, under Fe stress, to promote Fe acquisition by impacting extracellular Fe speciation. This process strongly relies on the ability of produced siderophores to compete with natural Fe sources to from soluble Fe complexes.
However, while siderophores achieve very high affinity for Fe, the complexation of Fe from oxids and organic matter sources is often affected by very low kinetics (several hours, days and more). This is a major constrain to metal acquisition, Fe homeostasis and bacterial growth. Our understanding of how siderophore-Fe complexes are retrieved by bacteria once formed in the extracellular matrix also remains elusive.
Besides the production of siderophores, another important feature of most microorganisms is their capacity to form multicellular communities embedded in a self-secreted extracellular matrix; biofilms.  Biofilms are ubiquitous in the environment, and provide many advantages for the microbial communities such as protection against environmental stresses and increased sharing of resources.
Here, I will present recent results showing that, in the model organism Bacillus subtilis, biofilm formation responds to intracellular Fe limitation. I will also show evidences that the production of the biofilm matrix improves the efficiency of siderophores to recruit Fe from unavailable sources. Finally I will discuss the importance to further study the role of biofilm formation on Fe, and other essential trace metals, acquisition in terrestrial, aquatic and marine (coastal and open-ocean) ecosystems.

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