The vast oceans are home to countless bacteria that face the challenge of obtaining scarce and unevenly distributed nutrients needed for growth and multiplication. Some bacteria have evolved into efficient hunters to tap into new sources of sustenance in the form of other microorganisms. Predatory bacteria like Myxococcus xanthus and Vampirococcus have been identified as successful hunters. In a new study by researchers at ETH Zurich, another predatory bacterial species called Aureispira has been discovered. This filamentous marine bacterium possesses molecular structures resembling grappling hooks and bolt guns that it uses to capture and kill its prey like a pirate raiding a ship.
Aureispira is a selective predator that only becomes predatory when nutrient concentrations are low in its environment. When the supply of nutrients is sufficient, the bacterium refrains from hunting and remains passive. However, when starved, Aureispira activates its predatory behavior and rebuilds its cannons and grappling hooks to capture prey. This lifestyle, known as ixotrophy, has been observed in marine samples by researchers in collaboration with the University of Vienna. The predatory behavior of Aureispira sheds light on its adaptive survival mechanisms in nutrient-deprived conditions.
The researchers utilized various imaging techniques, including light microscopy and cryo-electron microscopy, to understand the function and molecular structure of Aureispira’s grappling hooks and cannons. This allowed them to analyze the molecular structures in their cellular context without artifacts. By studying the molecular structures of the bacterium’s weapons, researchers gained insights into its predatory behavior and adaptive mechanisms. The availability of imaging techniques at ETH Zurich’s ScopeM competence center facilitated the detailed analysis of Aureispira’s predatory mechanisms.
The findings of the study are primarily driven by curiosity and basic research, according to lead researcher Martin Pilhofer. The team has been working for a decade to elucidate contractile injection systems, which are the pirate bacteria’s on-board cannons used for capturing prey. In other predatory bacteria, these systems are loaded with toxins to kill the prey instantly. It is possible that these bacterial bolt guns could be loaded with active substances to inject into individual cells with the help of a molecular machine. Additionally, predatory bacteria like Aureispira have the potential for practical applications such as combating algal blooms or controlling the proliferation of bacteria like Vibrio.
Predatory bacteria have shown efficiency in hunting down specific targets like cyanobacteria and blue-green algae. This feature suggests that they could be beneficial in addressing environmental issues such as algal blooms. By selectively preying on harmful microorganisms, bacterial predators like Aureispira could contribute to maintaining ecological balance in marine ecosystems. The study highlights the importance of understanding predatory bacteria’s behavior and adaptive mechanisms for potential applications in environmental management and microbial ecology. Overall, the discovery of Aureispira as a rare predatory bacterium sheds light on the fascinating strategies bacteria employ for survival in challenging environments.