New research shows that environmental changes can alter the hierarchical relationships between microbial predators and prey.In a new study, the predator-prey relationship of two bacteria grown in the laboratory was reversed after one of them was grown at lower temperatures. Marie Vasse of the French company MIVEGEC and colleagues published the findings on January 23 in the open-access journal PLOS Biology.
Previous research has shown that ecological context affects predator-prey relationships. For example, the similarity or contrast between the background color of a prey species and the prey's color can affect how easily a predator can spot its prey. In addition, predator-prey relationships sometimes switch, such as when two crustaceans prey on each other, and changes in surrounding salinity reverse which animal is dominant. However, there are few other known examples of this relationship shifting in response to abiotic ecological changes.
Some bacteria prey on other bacteria, and the ecological environment affects the efficiency of preying. Based on this understanding, Vasse and colleagues conducted several laboratory experiments to test how temperature affects the predator-prey relationship between two bacteria, Myxococcus xanthus and Pseudomonas fluorescens.
They found that when Pseudomonas fluorescens was grown in a petri dish at 32 degrees Celsius and then exposed to Myxococcus xanthus, the latter acted as a predator, killing the fluorescent bacteria in large numbers. However, when the fluorescent bacteria were grown at 22 degrees Celsius, the predator-prey relationship changed, and they killed the Myxococcus xanthus and obtained the nutrients they needed to continue growing.
The researchers conducted further experiments to better understand the mechanisms by which growth at colder temperatures might reverse predator-prey roles. They found a non-protein substance released by Pseudomonas fluorescens that is lethal to Myxococcus xanthus, and its production appears to be affected by temperature.
The researchers say their results suggest that many forms of microbe-on-microbe killing not traditionally associated with predation (where a killed organism is eaten by its killer) may actually lead to predation. They also note that in this study, the temperature at which P. fluorescens grew before encountering Myxococcus xanthus could determine which was the predator and which was the prey when the two species later met, highlighting the importance of considering historical context when assessing current predator-prey relationships.
This study and subsequent studies contribute to the understanding of natural ecology and practical applications, such as optimal use of certain microorganisms to control others.
"We find it fascinating that in microbial predation, relatively small changes in ecological factors can determine who kills whom and who eats whom," the authors added. "We suspect that microbe-on-microbe killing leads to predation much more frequently than previously appreciated."
Compiled source: ScitechDaily