Bacterial strains growing in a 3D colony can co-operate and become genetically diverse by sharing secreted factors
When scientists study bacteria in the lab, they often grow them as flat colonies on plates of nutrient jelly or as single cells in a liquid broth. Out in the real world, things are very different. Bacteria in natural environments grow in three-dimensional communities known as biofilms, which can be made up of several different types of bugs. To discover more about how bacterial cells interact in biofilms, researchers have been seeing what happens when two types of bacteria are grown together in different conditions. One strain is normal (the middle row, and in red top row), and the other carries an alteration in the alrA gene (bottom row, in green top), which is involved in making the essential nutrient alanine. Cells without alrA die if grown in flat or liquid cultures but they will survive in biofilms by feeding on alanine produced by the normal cells around them, revealing how bacteria can co-operate together.
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