Bacteria can be ruthless. A new study has shown that when their survival is threatened because of food scarcity, they will kill and consume neighboring microbes. The work, which was reported in Science, has determined that bacteria will utilize a special molecular machine called a Type VI Secretion System (T6SS) to attack, destroy, and absorb nutrients from other bacteria.
"The punchline is: when things get tough, you eat your neighbors," said senior study author Glen D'Souza, an assistant professor at Arizona State University. "We've known bacteria kill each other, that's textbook. But what we're seeing is that it's not just important that the bacteria have weapons to kill, but they are controlling when they use those weapons specifically for situations to eat others where they can't grow themselves."
T6SS machines are like tiny harpoon guns that bacteria use to penetrate and inject cells with toxins. It may be possible to harness T6SSs to create specialized probiotics, disease fighters, or better climate models, for some examples. Sometimes, that type of research and knowledge can have surprising, unexpected, and important applications.
It's been thought that a bacterium typically uses a T6SS when it needs space and decides to eliminate any rival cells. But this work has shown it goes beyond that; they also kill for food.
Microscopy showed that microbes could use T6SS to attack their neighbors when they lacked adequate nutrients, and then fed on the dead cells.
When the researchers genetically eliminated the T6SS, nutrient-starved bacteria simply could not grow. Unedited bacteria continued to destroy other cells and live.
The study also indicated that this is not simply a phenomenon seen in the lab; they also observed it in various conditions. "It's present in many different environments and it's operational and happening in nature from the oceans to the human gut," said D'Souza.
The work shows that we still have a lot to learn about microbes.
"Watching these cells in action really drives home how resourceful bacteria can be," said first study author Dr. Astrid Stubbusch, a former doctoral student at ETH Zurich. "By slowly releasing nutrients from their neighbors, they maximize their nutrient harvesting when every molecule counts, revealing a new link in the microbial food web that we've not appreciated before."
Sources: Arizona State University, Science