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Bacteria will turn to murder if they get hungry enough
Bacteria operate by a pretty simple set of biological commands: survive and reproduce. But a recent study is highlighting that, in some cases, the microscopic organisms will follow those commands by any means necessary. Even if it entails killing and devouring their fellow bacteria.
'The punchline is: when things get tough, you eat your neighbors,' said Glen D'Souza, an Arizona State University molecular scientist and senior author of the paper published June 12 in the journal Science.
D'Souza explained that while most bacteria absorb nutrients from the environment around them, it's 'textbook behavior' for certain species to kill each other. However, what he and colleagues observed was something different. In some instances, usually harmless bacteria will turn to violence if desperate.
'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,' D'Souza said.
'A microbial Jekyll and Hyde,' added Ferran Garcia-Pichel, ASU's director of Biodesign Center for Fundamental and Applied Microbiomics who was not involved in the study.
D'Souza's team focused on a specific process inside bacteria called the Type VI Secretion System (T6SS). Similar to a tiny harpoon gun, T6SS enables bacteria to shoot a microscopic, needlelike weapon loaded with toxins into neighboring cells and organisms, causing them to fatally tear apart. Previously, microbiologists believed that bacteria mostly used their T6SS to eradicate rivals and make space for their own growth.
But after utilizing timelapse imaging and other genetic analysis tools, the team recorded various bacteria using T6SS in a startling way. When nutrients were scarce, the organisms ambushed nearby bacteria and injected them with toxins. They then fed off of their targets as they essentially 'bled out.'
'By slowly releasing nutrients from their neighbors, they maximize their nutrient harvesting when every molecule counts,' said study first author Astrid Stubbusch.
To prove that this behavior was, in fact, intentional, the team genetically switched off the T6SS in sample bacteria, and then placed them into a nutrient-starved setting. Those without the ability to use their mini-harpoons eventually died, but the unaltered bacteria began killing to survive.'This isn't just happening in the lab,' D'Souza clarified. 'It's present in many different environments and it's operational and happening in nature from the oceans to the human gut.'
The ramifications go beyond microscopic horror stories. Understanding these systems allows researchers to gain a more complete picture of the microbial food chain and illustrate just how resourceful bacteria really are. It may also help pave the way for new antibiotics, or design drugs that harness T6SS to directly attack pathogens.
The observations also have implications outside the human body. Many ocean bacteria are responsible for helping regulate Earth's carbon cycle. If some of them are using T6SS to devour bacteria that break down algae and recycle carbon, then ecologists can study how these influence planetary ecosystems.
'Watching these cells in action really drives home how resourceful bacteria can be,' added Stubbusch.
