Eva Pouder
| Eva PouderMICROFOND : Study of the microbial communities involved in the iron cycle in deep marine hydrothermal environments. Ecological, physiological, metabolic and genomic aspect. Or How the deep-sea bacteria use iron to produce energy. |
Iron is a very important element to every life form. It’s also a source of energy for bacteria , enabling them to breathe, much as we do with oxygen.
Iron is the fourth most present element on Earth. It can be found in the ocean in, most of the time, very small quantities. Nonetheless, there are areas where it can be more present, especially around hydrothermal sources. The hydrothermal sources are big underwater chimneys. They spew hot water that can reach extreme temperatures (up to 400°C/752°F). This water comes from the seawater circulation, which enters the oceanic crust beneath oceans floor. When it infiltrates deeper in the oceanic crust, the water will heat up, react with rocks and exchange elements with it. This will change its chemical composition. When this water reaches a high temperature and is under pressure, it will rise before being expelled onto the seabed in the form of hydrothermal fluid through hydrothermal chimneys. Depending on their composition, fluids can be black, white or more transparent (we are talking about shimmering).
This water, loaded with metals, especially iron, is vital for bacterial community's structure. Without light, life near hydrothermal vents relies on chemical energy, not light. Microorganisms can use chemicals expelled by hydrothermal vents to make other organic molecules, like sugars and organic acids... Those molecules will be used by other microorganisms and by larger organisms (fauna). Because of the abundance of iron in those ecosystems and its importance for bacteria, iron is a key element in the hydrothermal systems. Nevertheless, nowadays, we do not really know about those metabolisms of iron, even less in the deep sea. Moreover, deep-sea mining is being considered by governments to extract minerals from these ecosystems to meet the need for mineral raw materials; this could seriously harm them. Eva wants to know how bacteria use iron. She also wants to know its evolution in the hydrothermal environment and how it could be redistributed in the ocean.
Why this subject ?
During her master's studies, Eva discovered the deep-sea environment which interested her greatly because it is truly atypical and extreme life forms. In fact, in the beginning she had initially opted for microbiology because she found the capabilities of microorganisms, « their powers », fascinating. This research topic allowed her to combine both with two complementary approaches:
- One approach in which she will work in the laboratory, making culture medium and growing environments to try to isolate new bacteria. This enable her to study them more precisely and to understand the diversity of organisms that may be involved in the iron cycle.
- Another approach is using molecular biology and bioinformatics. This approach is based on the DNA of bacteria. It can either target a single gene in the bacterial entire gene pool, acting like a barcode. You have then to scan it to identify the bacteria (metabarcoding). It can also target all the bacterial genes (the whole genome) to evaluate the genetic potential. This allows Eva to see if the bacteria in her samples have the genes required to carry out iron metabolisms (metagenomics).
A funny story related to this subject ?
During Ludivine Michaudet’s Master internship, they carried out enrichment cultures to try to isolate bacteria that could use iron. They succeeded in isolating a Vibrio species. Before Ludivine came for internship, Eva had already succeeded in isolating the same strain. These bacteria are known as heterotrophs, which means they use organic matter, but it was notknown that these bacteria could also develop without it. It seemed absurd at the time, and everyone laughed. Now they are writing the first paper on this subject.