Recently in Nature Communications, Professor Ferran Garcia-Pichel of Rakes and Regents reported on new bacteria that attack soil cyanobacteria in biocrusts. In this article, he describes the life cycle of the newly discovered predator, its attack mechanism and its ecological impact.
Bacteria are everywhere and play an important role in maintaining ecological processes around the world. For example, in desert soils, cyanobacteria use photosynthesis to produce energy.
Similar to plants, their role in oxygen production and nitrogen fixation is essential for the survival of other organisms. Cyanobacteria form communities that live on the soil surface, forming biocrusts. These communities provide great benefits by trapping dust, preventing erosion and increasing soil nutrients and water levels.
Unfortunately, and despite their role in maintaining ecosystems, cyanobacteria are the preferred prey of a newly discovered predator: Candidatus Cyanoraptor togatus (C. togatus).
“There was something killing the biocrusts. It was not a virus and it was not a small animal. It can only be another bacteria,” Garcia-Pichel said.
Healthy cyanobacteria biocrusts look like soil when dry, but when wet, their green pigmentation is visible.
Biocrusts that have been attacked by Cyanoraptor show releases of cyanobacteria in circular patterns, known as plaques, similar to tiny fairy rings. In the field, the researchers were able to identify the disease by looking at these unusual plaques.
“I first saw them in Casa Grande, Arizona (USA) and then continued this process of watching storms and immediately fleeing into the countryside, sometimes driving six hours or more to spot them. at various locations in the Sonoran and Chihuahuan deserts,” said Julie Bethany Rakes, Ph.D. by Arizona State University and lead on the discovery.
Cyanoraptor’s modus operandi
They worked in the field and in the laboratory to isolate pathogenic bacteria. After isolation, the bacteria were cultured and their life cycle and attack mechanism were established.
At an early stage, Cyanoraptor spreads in the form of small spherical cells called propagules. These cells neither grow nor divide.
Instead, they hide and wait patiently for their prey. When the cyanobacterium gets close enough, the Cyanoraptor attacks, attaches to the prey, and forms a specialized docking structure, dissolving the prey’s skin-like cell wall and entering the prey’s cell.
Cyanoraptor propagules are weird when it comes to bacteria. They have an outer compartment connected by two membranes.
The researchers suspect that this compartment plays a key role in the attack, trapping and releasing proteins that break down the outer membrane of their prey and allow them to enter the weakened cell body.
This compartment is also how the Cyanoraptor gets its name from its species, togatus, as they appear to be wrapped in a cloak or toga.
Once inside, the Cyanoraptor eats the prey, becoming a sausage-like cell.