Like us, many algae need vitamin B12. We get our vitamins from the food we eat or by taking vitamin supplements. But how do simple, single cell organisms like algae get the nutrients they need?
Vitamins are essential for a healthy life, but the organisms that depend on them cannot produce them. Vitamin B12 is the most structurally complex of all vitamins and therefore it is very costly for organisms to produce it. Within all the kingdoms of life only a few prokaryotes (species like bacteria that lack a nucleus) are capable of making this important nutrient.
Plants do not produce or need vitamin B12 and therefore it is not present in plant-based food. In humans, B12-deficiency can lead to a type of anaemia, which means that red blood cells cannot effectively transport oxygen around the body. This means that vegetarians and vegans often take B12 supplements to maintain a healthy diet.
For humans and for more than half the known species of algae, B12 is needed to enable the production of methionine, one of the 21 amino acids that form the building blocks of proteins. How do algae acquire this vital nutrient? Either there is enough B12 in the environment so that it is readily available to them or algae need to find an active source of the vitamin.
I work with algae that can get their vitamin B12 from bacteria. But why would bacteria share such a vital chemical with other species? The hypothesis that we are testing assumes that the bacteria get something in return.
Like plants, algae are photosynthetic. This means they are able to use the energy from light to convert carbon dioxide and water into high energy carbon-containing products. The B12-producing bacteria are not photosynthetic and therefore need this carbon as an energy source for their growth. This is an example of a mutualism, where both species benefit from the presence of the other.
To track the carbon exchange from the photosynthesising algae to the bacteria I use a heavy version of carbon in a technique called stable isotope labelling. I then use a highly sophisticated instrument (a Secondary Ion Mass Spectrometer) to break down the material of the cells and pass it through a magnet in order to separate and detect the different carbon masses. This information can then be used to deduce how the carbon produced by algae is used by bacteria.
Algae are often discussed as potential ‘cellular factories’ for the sustainable production of chemical products in the cosmetic and food supplement industries as well as for biofuels. A major challenge is how to efficiently grow algae on a large scale. A better understanding of what algae need to maintain a healthy growth means we could apply this knowledge to industrial-scale applications.
Image is student’s own microscope image combined with an image from https://morguefile.com/search/getty/1/vitamins%20spoon/