Morning everyone. My name J.B. Raina and together we're going to go in a journey and I'm going to show you the ocean as you probably have never seen it. Do you know that there's more than one million bacterial cells in every drop of seawater? That means that there's more bacteria in just ten liters of seawater than human on this planet. Now in people's mind the word bacteria and disease are usually closely related. And although it's true that a few bacteria can make you very sick, the vast amount the large number of bacteria in the oceans are not playing against us but for us. I'll give you a quick example the bacteria here on the picture, is the single most abundant photosynthetic organism on this planet. Its name is proprio caucus and it produces a quarter of the oxygen we breathe every day. That's right. You can thank this organism in once every fourth breath you take but what's even more astonishing is that we didn't even know it existed until 1988. That tells you how little we know about the bacteria living in oceans. What we start to realize though is that from the point of view of a mine microbe the ocean is far from being homogenis. This is an artistic drawing of how a drop of seawater might look like from the point of view of a mine bacteria and what you can see in this picture is that there is a lot of heterogeneity you have a lot of nutrient hotspots surrounding particles. Nutrients are like food for bacteria and you have these nutrient hotspots surrounding that sinking particles.
You have this nutrient hotspot surrounding small microbial cells. And you also have these nutrient hotspots surrounding the pool of larger organisms like copepods. What bacteria do they use a behavior called chemotaxis to get closer to this nutrient hotspots and to be able to sustain their growth. Chemotaxis is like the ability of bacteria to swim towards chemicals they like. If I take the analogy back to human scale, me being French, I'm chemotactic towards the smell of freshly baked croissants. Alright. So that gives you an idea. If you if you put the smell of croissant I'll I'll get there. It's the same for bacteria. They will respond strongly to certain smell. What's very important is that these chemotactic behaviours are extremely important at the oceanic scale because bacteria gets to higher level of nutrients that can sustain their growth this chemotactic behaviour truly drives oceanic productivity and feeds the base of the mind food web. This is important because that support of fisheries. Chemotactic behaviour also determines how much carbon stays in the ocean and how much carbon goes back into the atmosphere and that has an impact on our climate. However, up until now we still have no idea and no way to study chemotaxis directly in the ocean. But that's what I've been working on I've developed a new assay called Insitute of Chemotaxis assay.
It's slightly larger than the credit card and it's made out of an array of wells. Each well can be filled with a different substance, a different nutrient something that bacteria might like and you deploy this device in the ocean and the chemicals in the well start diffusing out creating these nutrient hotspots like I told you about earlier. Chemotactic bacteria can sense these hotspots and swim towards the smell that they prefer. If one bacteria is French it will go towards the smell of croissant right? So by sampling these wells we can start to answer which bacteria is attracted to what nutrients and start to understand the processes that sustain the health of oceans.
Thank you very much.
6 September 2018
Jean-Baptiste Raina goes in small when he tackles the big issues! A marine microbial ecologist, he’s looking at how microbes in the ocean interact and impact on the environment and the global climate.
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