Researchers discover new bacteria that are damaging our ecosystems

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.

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Researchers discover new bacteria that are damaging our ecosystems

Once inside its prey, Cyanoraptor lodges itself in the bacterium’s cytoplasm and begins to replicate – growing and dividing until it finally kills the prey and releases a new army of cells. ‘offensive.

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.

1664356336 145 Researchers discover new bacteria that are damaging our ecosystems1664356336 145 Researchers discover new bacteria that are damaging our ecosystems
Rakes researching Cyanoraptor in the desert (Image: Handout/Julie Bethany Rakes)

When this is long enough, this predator begins to divide into several cells at once, eventually killing the prey and becoming propagules again, waiting for the next victim.

“It’s a predator that gets into the cells of its prey and eats it from the inside, which is horrible,” Garcia-Pichel said. “It really is like a microbial horror movie. »

As the cyanobacteria die off, all the things the biocrusts do to benefit the desert disappear. Valuable properties such as nitrogen cycling, dust retention and moisture retention are significantly reduced.

“Overall, this indicates that there may be serious consequences for desert health, less nutrients, less soil stability and water retention, which reduces the time that plants and other organisms may be active.

With the loss of these functions, organisms that depend on these activities, such as plants, may suffer, which may have additional consequences up the food chain,” Rakes said.

Rakes’ discovery also demonstrated that predatory bacteria can shape the structure and function of microbial communities around the world, which isn’t just an interesting biological rarity.


Feature Image: Disclosure/Julie Bethany Rakes

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