This research found that the beneficial gut bacteria Lactobacillus rhamnosus GG (LGG) interacts and facilitates (modifies the activity) of other gut bacteria. This isn't surprising. All our microbiomes are communities or ecosystems of microbes. But the really important bacteria have been called keystone species by other researchers. From Medical Xpress:
In recent years, research into the benefits of gut bacteria has exploded. Scientists across the globe are examining how these microbes can help improve health and prevent disease. One of the most well-known of these is Lactobacillus rhamnosus GG (LGG). This strain of bacteria, which is part of many popular probiotic products, has a reputation as a helpful microbe. Researchers have found evidence that it can help with intestinal problems, respiratory infections and some skin disorders. Some research suggests that it may even help with weight loss. But a key question has remained unanswered: How does LGG actually produce benefits?
Now, researchers at the University of Maryland School of Medicine (UM SOM) have come up with an explanation. It appears that LGG may act as a facilitator, modifying the activity of other gut bacteria....Claire M. Fraser, PhD, professor of medicine at the UM SOM, as well as director of the Institute for Genome Sciences, studied the effect of LGG on a group of elderly subjects.
She and her collaborator, Dr. Patricia Hibberd at Massachusetts General Hospital, tested 12 subjects, who ingested LGG twice a day for 28 days. She analyzed gut bacteria before and after this regimen, and found that ingesting LGG led to increases in several genes that foster several species of gut bacteria, including Bacteroides, Eubacterium, Faecalibacterium, Bifidobacterium and Streptococcus. These microbes have been shown to have a range of benefits in humans, including the promotion of a healthy immune system. (Fraser notes that LGG may also have direct effects, in addition to its ability to modify the overall ecosystem.)
"This is a new idea, that some probiotics may work by affecting the overall ecosystem of the gut," said Prof. Fraser. "Previously we tended to think that LGG and other probiotics worked directly on the host. I think this finding has many exciting implications." For one, Fraser says, it lends support to the idea that we need to look at the microbes in the gut as an interconnected ecosystem rather than a series of solitary bacteria. Modifying the behavior of microbes already in the gut may be just as important as adding any single species to this population.