Scientists in the United States have made an important discovery about how certain bacteria living in the human gut may contribute to colon cancer.
Their findings help explain how a toxin made by these bacteria can directly damage human DNA. The research was published in the journal Science and provides the clearest explanation so far of how this toxin works inside the body.
The toxin is called colibactin. It is produced by certain strains of bacteria, including some forms of Escherichia coli, or E. coli. These bacteria are normally part of the community of microbes that live inside the human digestive system.
The human gut contains trillions of microorganisms, often called the gut microbiome. Many of these microbes are helpful and support digestion, immune health, and nutrient absorption. However, some strains of bacteria can produce substances that may harm the body under certain conditions.
Scientists have known about colibactin for several years. Earlier research suggested that the toxin could damage DNA and may be linked to colorectal cancer, which is one of the most common cancers worldwide.
Despite this suspicion, studying colibactin has been very difficult. The molecule is extremely unstable and breaks apart quickly, making it hard for scientists to observe and analyze it directly.
In the new study, researchers used powerful scientific tools to finally examine the toxin in detail. They applied advanced techniques such as mass spectrometry and nuclear magnetic resonance spectroscopy.
These tools allow scientists to analyze molecules at the atomic level and understand their structure and behavior. With these methods, the research team was able to uncover how colibactin interacts with human DNA.
DNA is the molecule that contains the instructions that guide how our cells grow, divide, and repair themselves. If DNA becomes damaged, the cell may not function normally. Sometimes the damage can be repaired, but if the repair process fails, mutations can develop. Over time, these mutations can lead to cancer.
The researchers discovered that colibactin does not damage DNA randomly. Instead, it targets very specific areas of the DNA molecule.
These areas are rich in two of the four basic building blocks that make up DNA, known as adenine and thymine. Because of the shape and electrical properties of the colibactin molecule, these regions of DNA are particularly vulnerable.
The toxin forms a strong chemical bond between the two strands of DNA. Scientists call this type of damage an interstrand cross-link. In this situation, the two strands of the DNA double helix become stuck together like they have been glued.
When this happens, the cell cannot properly copy or repair the DNA. This type of damage is considered extremely serious because it interferes with essential processes that keep cells healthy.
Another important discovery from the study is that colibactin attacks a specific part of the DNA structure known as the minor groove. The minor groove is a narrow channel that runs along the twisted DNA helix. In this region, the two outer backbones of the DNA molecule are closer together.
The scientists found that the central part of the colibactin molecule carries a positive charge and is chemically unstable. This allows it to be attracted to the negatively charged environment inside the minor groove of DNA.
The researchers described this interaction as similar to a lock-and-key mechanism. The toxin fits into the groove in a way that allows it to attach precisely where it can cause the most damage.
This discovery gives scientists a much clearer picture of how colibactin functions at the molecular level. The researchers say this mechanism is unlike anything previously observed in natural toxins produced by bacteria.
The findings may also help explain why doctors often see similar patterns of DNA mutations in patients with colorectal cancer. If colibactin repeatedly damages DNA in the same way, it can leave recognizable marks in the genetic material of cancer cells.
Understanding how this toxin works could lead to several important advances in medicine. For example, scientists may be able to develop tests that detect the presence of colibactin-producing bacteria in a person’s gut. People who carry higher levels of these bacteria might have a greater risk of developing colorectal cancer.
Researchers may also explore ways to block the toxin before it damages DNA. Future treatments could potentially prevent colibactin from forming or stop it from binding to DNA inside cells.
Another possibility is modifying the gut microbiome itself. Changes in diet, probiotics, or other therapies might help reduce the number of harmful bacteria that produce colibactin.
Overall, the study represents a major step forward in understanding the link between gut bacteria and cancer. It shows that certain microbes living in the digestive system can directly damage human DNA in ways that may lead to cancer.
As scientists continue studying this process, the discovery could lead to better screening tools, earlier detection of cancer risk, and new strategies to protect people from colorectal cancer in the future.
For more information about gut health, please see recent studies about the crucial link between diet, gut health, and the immune system and results showing that Low-gluten, high-fiber diets boost gut health and weight loss.
For more information about gut health, please see recent studies about Navigating inflammatory bowel disease (IBD) with diet and results showing that Mycoprotein in diet may reduce risk of bowel cancer and improve gut health.
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