Predatory bacteria – bacteria that eat other bacteria – grow faster and consume more resources than non-predators in the same soil, according to a new study released this week by Northern Arizona University. These active predators, which use the behavior of the wolf pack, enzymes and cytoskeletal “fangs” to hunt and feast on other bacteria, wield significant power in determining where soil nutrients go. The results of the study, published in the journal mBio This week, to show that predation is an important dynamic in the wild microbial realm, and suggests that these predators play a disproportionate role in how elements are stored or released from the soil.
Like all other life forms on earth, bacteria belong to complex food webs in which organisms are connected to each other through whom they consume and how. In macro-webs, environmentalists have long understood that when resources such as grass and shrubs are added to the lower levels of the web, predators at the top, such as wolves, often benefit. The research team, led by Bruce Hungate and researchers from the University of Northern Arizona and the Lawrence Livermore Laboratory, wanted to test whether the same was true in microbial food webs found in wild soil.
“We know that predation plays a role in maintaining healthy soils, but we hadn’t appreciated how important predatory bacteria are to these ecosystems until now,” said Hungate, who heads the Center for Ecosystem. Science and Society at Northern Arizona University.
To understand who and how many predatory bacteria were consuming, the research team took the big picture using dozens of small “snapshots” of data: 82 datasets from 15 sites across a range of ecosystems. The team used information about the behavior of bacteria in culture to classify bacteria as obligate or facultative predators. About seven percent of all bacteria in the meta-analysis were identified as predators, and the majority of them were facultative or omnivorous.
Obligate predatory bacteria like Bdellovibrionales and Vampirovibrionales grew 36% faster and absorbed carbon 211% faster than non-predators. When the soil received a boost of carbon, predatory bacteria used it to grow faster than other types. The researchers also found these effects in omnivorous bacteria, although the differences are less profound.
All of the experiments were conducted using a state-of-the-art technique called quantitative stable isotope probing, or qSIP. The researchers used tagged isotopes, which act much like molecular hashtags, to track who is active and absorbing nutrients in the soil. By sequencing DNA in a soil sample and looking for these tags, the team were able to see who was growing and eating who in bacterial taxa.
“When analyzing my data, I noticed that Vampirevibrio was super enriched. Since we know Vampirevibrio is a predator, I was interested in looking for other potential predators in my other data, ”said Brianna Finley, a postdoctoral researcher at the University of California-Irvine and co-author of the study. validates qSIP as a tool. “
Soil ecosystems contain more carbon than what is stored in all plants on Earth, so understanding how carbon and other elements move between soil organisms is critical to predicting future climate changes. And because bacteria are so abundant in the soil, they play a huge role in how nutrients are stored or lost there. And knowing more about how predatory bacteria act like “antibiotics” could have therapeutic implications, later.
“So far, predatory bacteria have not been a part of this soil story,” Hungate said. “But this study suggests that they are important people who have an important role to play in determining the fate of carbon and other elements. These findings motivate us to take a closer look at predation as a process.”
Besides Hungate, the other authors of the NAU are Jane Marks, professor in the Department of Biological Sciences; Egbert Schwartz, professor in the Department of Biological Sciences; graduate research assistant Pete Chuckran, Paul Dijkstra, research professor in the Department of Biological Sciences; graduate student Megan Foley; Michaela Hayer, Research Associate for Scotland; Ben Koch, Principal Investigator for Ecoss; Michelle Mack, professor in the Department of Biological Sciences; Rebecca Mau, Research Associate, Pathogen & Microbiome Institute; Samantha Miller, Research Associate for Scotland; Jeff Propster, research assistant for Ecoss; graduate research assistant Alicia Purcell; and former NAU researcher Bram Stone.
The research was supported by the Office of the Biological and Environmental Research Program of the Department of Energy and Genomic Sciences, and a Lawrence Fellow Award from the Lawrence Livermore National Laboratory.