Human Gut Bacteria Have ‘Sex’ to Share Vitamin B12

 

Vitamin B12 is one of the essential nutrients that is required for the growth and development of different body parts, including the brain, blood cells, nerves, in humans. Without this nutrient, many living cells, including, bacteria can not function. Thus, beneficial gut bacteria share the ability to capture this nutrient with one another.

“The process involves one cell forming a tube that DNA can pass through to another cell,” said Patrick Degnan, UCR microbiologist and study head. “It’s as if two humans had sex, and now they both have red hair.”

Scientists have been aware of this process for years. They knew that ‘jumping genes’ were responsible for transferring DNA between organisms. Many studies have shown that these genes helped bacteria stay alive in the presence of antibiotics (medicines that fight bacterial infections).

“We’re excited about this study because it shows that this process isn’t only for antibiotic resistance. The gene exchange among microbes is likely used for anything that increases their ability to survive, including sharing vitamin B12,” said Degnan.

He also worked on similar projects earlier and found an important transporter responsible for capturing vitamin B12 into gut microbes. Recently, he was studying ‘jumping genes’ to know what information they were transferring. Later, he recognized that transporters were acting like cargo for B12.

Degnan and his team carried out experiments to verify what they suspected. They mixed bacteria that could transport B12 and some that couldn’t. On a dish, bacteria having B12 transporters formed a tube-like structure called sex pilus. This facilitated DNA transport between bacteria. Further, the bacteria that couldn’t transfer B12 were alive and got transporter genes. They did further experiments to examine the genome (complete set of DNA) of the bacteria. Moreover, the experiment was also successful in mice gut as well, other than just on the dish.

“In a given organism, we can see bands of DNA that are like fingerprints. The recipients of B12 transporters had an extra band showing the new DNA they had got from a donor,” said Degnan.

During the study, scientists used Bacteriodes, a beneficial gut bacteria that reside in the large intestine of most humans. These are anaerobic bacteria that grow in the absence of oxygen. They help to break down carbohydrates into simple molecules for energy production.

“The big, long molecules from sweet potatoes, beans, whole grains, and vegetables would pass through our bodies entirely without these bacteria. They break those down so we can get energy from them,” said Degnan.

Bacteroides and some other bacteria form a barrier across the human gut to protect it from pathogens. To explain this better, researchers gave an example of a previous study led by co-author Ansel Hsiao. He showed that some humans have microbe communities (microbiome) in their gut that prevent them from cholera. Further, they suggested that knowing how to keep these bacteria healthy can help people improve their health based on the functions they perform.

“There’s no way to have a healthy microbiome, but generally, having a diverse community of anaerobic bacteria is a healthy thing and can have beneficial effects,” said Degnan.

The detailed research has been published in the journal Cell Reports.