Some species of archaea – long thought to be a benign subdomain of commensal microbes – may promote colorectal cancer development by feeding on bacteria known to play a causative role in the disease.
A recent international study
The researchers, led by researchers at the Medical University of Graz in Austria, used advanced metabolic modeling to show that organisms in the archaea – especially…
Methanobrevibacter smithii– Facilitating the growth of bacteria associated with CRC e.g Spindle nucleus.
“For a long time, archaea were considered harmless organisms in the gut,” he explains Christine Muesl-Eichingermember of the Med Uni Graz research team. “Our results now show that, from a functional point of view, they are much more deeply involved in negative microbial processes than previously assumed.”
“Our experiments show that archaea can influence the growth of some cancer-associated bacteria, without being pathogenic.”
—Alexander Manhart, Medical University of Graz
The researchers studied nearly 3,000 metagenomic samples from 19 clinical studies covering twelve countries. The samples were obtained from people with a wide range of health conditions including inflammatory bowel disease, type 2 diabetes, and neurological disorders.
Using co-culture and advanced analytical techniques, researchers were able to study metabolites produced by various gut symbionts, as well as network interactions between different classes of organisms. Furthermore, they can identify microbial ecosystem patterns associated with specific diseases.
A very consistent result has been an increased prevalence of ancient monuments M. Smithy In patients with colorectal cancer, to a much higher degree than seen in normal people or those with other conditions.
Indirect effects
M. Smithy Able to take the byproducts of hydrogen and carbon dioxide from other gut bacteria, and convert them into methane. This in turn enhances the natural bacterial fermentation processes of other gut bacteria, and is generally nothing harmful to them. “This type of metabolic cooperation is a natural component of the gut ecosystem,” explains co-author Alexander Mannert.
Archaea have been shown to be major contributors to the chemical and microbial diversity of the gut environment, and researchers are only beginning to understand the role these exotic organisms play, emphasizes lead author Ruksara Mohammadzadeh.
But since this metabolic cooperation is essentially a neutral process, there is always the possibility that archaeologists will like it M. Smithy Unfriendly or even pathogenic organisms will be fed, as well as benign commensals.
“Our experiments show that archaea can influence the growth of some cancer-associated bacteria, without being pathogenic,” Mahnert explained.
One such organism linked to cancer is… F. corewhich were identified in higher amounts in colon tumor tissue, compared to colon tissue in healthy people. Animal study 2013
Alexander Kostek, a researcher at Harvard University, and his colleagues suggest so F. core It creates a pro-inflammatory environment in colon tissue and may have an oncogenic effect by selectively recruiting tumor-infiltrating myeloid cells.
The strong interrelationship between M. Smithy and F. core Which Graz’s team observed in tissue samples from colorectal cancer patients suggests that the former facilitates the growth of the latter, thus indirectly contributing to the carcinogenic process.
Unique range
Although archaea share many morphological features with bacteria, they possess unique structural and metabolic features that make them distinct from both eukaryotes and prokaryotes.
Many genera within the archaea range have cell membranes composed of ether-bound lipids, a feature never seen before among eukaryotic or prokaryotic bacteria. Some have a structure called archaea, which are functionally similar but morphologically different from bacterial flagella. One of the most important features is that many archaea produce methane. This is the factor that makes them major players in the human and animal intestinal microbiome.
Archaea are found throughout the natural world, and some are able to thrive in extreme environments such as hot volcanic springs. In the human microbiome, archaea are found in the mouth, intestine, and on the skin. Symbiont archaea are able to use a wider range of energy sources than eukaryotic cells. This includes sugars, ammonia, metal ions and hydrogen gas.
Master of mutuals
Archaea are ingenious mutualists, partly because of their ability to generate methane. By forming mutualistic associations with healthy commensal bacteria, they play key roles in regulating microbial diversity and stabilizing the gut microbiome. Because of this, they facilitate digestion for their animal hosts.
One of the most interesting examples of archaeal mutualism is the relationship between methanogenic archaea and certain protozoa within the digestive tract of termites. These protozoa are able to break down plant cellulose, which provides energy for termites. But this process generates a lot of hydrogen waste, which reduces energy production. Archaea convert hydrogen into methane, thus increasing the energy production of the protozoa.
An underrated item
“Archaea in the human gut are essential components of microbial networks and should receive greater attention in the future when interpreting microbiome data,” the Graz researchers wrote. Until recently, they believe that archaea were an understudied and understudied component of the gut microbiome.
This new research indicates that “changes in archaeological communities are disease-specific and highly variable.” The strong interrelationship between M. Smithyand F. core Other cancer-associated bacteria raise important questions and suggest the possibility of new directions in cancer research.
However, the Graz team emphasizes that their study “provides no evidence that archaea a reason “Cancer” should not be misunderstood as indicating a direct causal relationship. “Instead, the data suggest that the microbial network within the gut changes over the course of the disease — and that archaea are part of these adaptations.”
They say this opens new perspectives on the etiology of colorectal cancer, and perhaps other types of cancer.
“Our goal is to understand the microbiome as a dynamic system,” says Dr. Muesel Ischinger. “Only in this way can we determine which microbial populations contribute to health, and which undergo changes during the course of the disease.”
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