A study found that intestinal bacteria influence the growth of fungi.

The amount of fungi from the genus Candida, which has the potential to cause disease, can be determined by the bacteria that are found in the intestine. Among them, shockingly, are lactic-corrosive microscopic organisms that are known for their defensive impact against parasitic contamination. The discoveries of analysts at the Leibniz Foundation for Normal Item Exploration and Disease Science (Leibniz-HKI) and their cooperative accomplices from Denmark and Hungary add one more part of the riddle of understanding the human stomach microbiome.

The microbiome of the human gut is a very complex community in which various microorganisms keep each other under control. However, if antibiotics or other environmental factors cause an imbalance, individual species may spread and cause infection. Parasites of the Candida sort, for instance, are available in the digestive organs of numerous solid individuals. In most cases, they are not harmful, but they can also cause serious systemic infections.

It is difficult to study these interactions in the intestine. The laboratory can only partially cultivate the hundreds of species of bacteria and fungi, and many of them are unknown. As a result, metagenome research is being utilized by researchers at the Leibniz-HKI to gain a deeper understanding of the intestine.

“We discovered an increased number of lactic acid-producing bacterial species, including Lactobacillus species. It’s an unexpected discovery. I couldn’t believe it at first, so I double-checked numerous times, with the same result.”

Bastian Seelbinder, lead author of the study. 

Stool samples from 75 cancer patients were examined by the researchers for the study, which was recently published in Nature Communications. They discovered that certain bacterial species always appear in greater numbers when there are also a lot of fungi from the Candida genus. Bastian Seelbinder, the study’s lead author, explains, “Based solely on bacterial species and amounts, we developed a computer model that was able to predict the amount of Candida in another group of patients with an accuracy of about 80%.” The majority of these bacteria were oxygen-tolerant species.

A surprising result was found in Seelbinder’s work in the Microbiome Dynamics department at Leibniz-HKI, which is led by Gianni Panagiotou and focuses heavily on the gut microbiome. Not only was the prediction of the amount of fungi based on the bacterial species present accurate, but also which bacteria were associated with high fungi counts surprised the researchers. We tracked down an expanded number of bacterial species that produce lactic acid, including Lactobacillus species,” Seelbinder makes sense of. He had no idea what he was going to find. “At first, I couldn’t believe it, so I checked multiple times, each time with the same result.”

The justification for his amazement: Several studies have demonstrated that lactic acid bacteria protect against fungal infections. Panagiotou’s team also published one of them last year in the journal Nature Communications. “The result once again demonstrates how difficult it is to decipher the interactions of various microorganisms and how complex the human gut microbiome is,” says Panagiotou.

Anecdote from the researchers: Candida growth is aided by lactic acid bacteria, particularly those belonging to the genus Lactobacillus, which also reduce the fungus’s virulence. This could be because Candida species have the ability to alter their metabolism in order to utilize the lactate produced by lactic acid bacteria. This gives them an upper hand over different organisms, for example, Saccharomyces cerevisiae, as the scientists found in extra tests. However, it appears that the metabolic switch also prevents Candida from forming fungal hyphae that could invade the intestinal mucosa and keeps it in its typically harmless spherical yeast form.

Systems for high-risk patients
“There is likewise an idea that specific gatherings of Lactobacillus species could make various impacts,” Seelbinder says. The next step in this investigation will be more in-depth genomic analyses of the bacteria.

Panagiotou explains, “For the current study, we examined stool samples from cancer patients who are especially at risk for fungal infections.” To develop long-term strategies for at-risk patients based on their microbiome, samples from healthy subjects could be included in subsequent studies.

The Leibniz-HKI researchers collaborated with teams from the Technical University of Denmark, the Korányi National Institute of Pulmonology in Hungary, and Jena University Hospital, among others, for their research.

More information: Bastian Seelbinder et al, Candida expansion in the gut of lung cancer patients associates with an ecological signature that supports growth under dysbiotic conditions, Nature Communications (2023). DOI: 10.1038/s41467-023-38058-8

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