Partnerships between microbes lead to human disease

The fungus Rhizopus germinates and forms hyphae as part of the infection process.

New research has found that the fungus Rhizopus fights soil predators and human immune cells by collaborating with a bacterium called Ralstonia in a bilateral partnership.

The microscopic world is amazingly reminiscent of our world. The environment is inhabited by microbes that live in complex communities – some friendly and some not very. Microbes compete with each other for resources and also have to hide from predators or fight them. One example of this is a fungus Rhizopuswhich grows in soil and on spoiled food and is the cause of outbreaks of “black fungus” in Covid patients.

In the soil its predator is an amoeba Dictyostelium, a unicellular microbe that can move through the soil and absorb Rhizopusby absorbing it to produce nutrients. Scientists from the Universities of Exeter and Birmingham have found Rhizopus fights this predator by collaborating with a bacterium called Ralstonia in a bilateral partnership. Living inside Rhizopus, Ralstonia hiding from a predator. In turn, Ralstonia does the toxin that Rhizopus can use to neutralize the predator by not allowing it to feed on steam.

Why does it matter to human disease? Our immune cells are very similar to predators Dictyostelium: They seek out, absorb and destroy foreign microbes that enter our body, protecting us from infection. That means Rhizopus and Ralstonia can use the same strategy to avoid predators in the soil to escape our own immune system. Learning to fight predators in the soil, Rhizopus also learned how to cause disease in humans.

This work has shown that in her partnership with Ralstonia disturbed, animals infected with Rhizopus able to survive this devastating disease. Hopefully thanks to a better understanding of ecology and survival strategies Rhizopus and other pathogens that are used under normal conditions, we will be better prepared to fight these microbes if they cause human disease.

“This work is really important because, although it has been known that fungal-bacterial partnerships in soil have been affecting plant diseases for many years, this is the first example of a bacterial-fungal partnership that promotes mucarmycosis in humans. We hope this will help us develop better strategies for treating this devastating disease, ”said Dr. Elizabeth Balu, one of the project’s lead researchers.

This work was supervised by Dr. Herbert Itabangi, who was a joint student of Dr. Elizabeth Balu (Exeter) and Dr. Kerstin Feltz (Birmingham). Dr. Itabangi was funded by the Wellcome Trust Strategic Award (led by Professor Neil Gow in Aberdeen). Dr. Itabangi’s discovery is a key step forward in our understanding of the “black fungus” that causes mucormycosis and was responsible for nearly 40,000 deaths in 2021.[{” attribute=””>COVID-19 pandemic.

Reference: “A bacterial endosymbiont of the fungus Rhizopus microsporus drives phagocyte evasion and opportunistic virulence” by Herbert Itabangi, Poppy C.S. Sephton-Clark, Diana P. Tamayo, Xin Zhou, Georgina P. Starling, Zamzam Mahamoud, Ignacio Insua, Mark Probert, Joao Correia, Patrick J. Moynihan, Teclegiorgis Gebremariam, Yiyou Gu, Ashraf S. Ibrahim, Gordon D. Brown, Jason S. King, Elizabeth R. Ballou and Kerstin Voelz, 7 February 2022, Current Biology.
DOI: 10.1016/j.cub.2022.01.028 Partnerships between microbes lead to human disease

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