*For medical professionals only
The intestinal microbiome can be regarded as the first "jack of all trades" in our human body, no matter what physiological and pathological problems, it seems to be able to mix a foot. But don't let these sideways ignore the work of the fungi, such as resisting foreign invasions.
One of the main health benefits of intestinal bacteria is the prevention of pathogen colonization and subsequent infection, a function known as colonization resistance. The ability to resist colonization is also different among bacteria, and some research evidence has found that there are also heroic units in the intestinal bacteria that are better than other bacteria.
Most of these anti-enemy heroes' superpowers have several directions, competing with pathogens in nutrition and living space, directly antagonizing toxins or other harmful compounds, and promoting the host's immunity to pathogens.
Today, the scientific team of the University of Oxford published an article in the journal Science, and the researchers found that in the matter of resisting foreign enemies, "the strength of many bacteria" is also a very important point!
It turns out that colonization resistance is actually a complex ecological trait. The experimental results showed that the resistance of a single species to pathogens was very limited, but when the diversity of microflora rose to 50 bacteria, the growth of pathogens was greatly limited. Of course, "hero strains" still exist, but they only work in highly diverse groups.
Hero strains are also easy to predict, and researchers have found that the higher the overlap with pathogen metabolism, the more likely it is to become the core of colonization resistance, and we can even use this to infer the composition of the microflora that can protect the body from drug-resistant bacteria!
Diagram of the title of the dissertation
In order to test the ability of intestinal bacteria to fight enemies, the researchers screened out 100 different human intestinal commensal bacteria, and the hypothetical enemies were Klebsiella pneumoniae and Salmonella typhi.
Since the competition between enterobacteria and pathogens has two modes, one is the ecological invasion mode when the pathogen has just entered the intestine, and the other is the competition mode in which the pathogen grows together under the same conditions, so the researchers also designed two corresponding experiments, and selected 10 "anti-enemy pioneers" with comprehensive scores.
Again, the ten contestants underwent a more rigorous custom resistance test, participating in two competitive modes at once and testing for pathogen abundance after 24 hours.
Experimental procedure
Although the 10 players were already the best of the best, the test results were not good...... Each strain is weak on its own, and most do not show colonization resistance at all.
Escherichia coli, which is known to compete with Salmonella typhi, but was also very effective in providing protection, with pathogen abundances eventually reaching 108 and 109 cells/ml, respectively.
But if 10 players attack together, the result is very different, and the abundance of the two bacteria is suppressed by 2-3 orders of magnitude!
Ten is better than one can fight (。
The researchers continued to increase the number of strains, and as can be seen from the figure, the more strains, the higher the diversity of the microflora, and the stronger the resistance to colonization of pathogens.
At the same time, the presence of E. coli is also very necessary, and only E. coli has the ability to resist colonization, but conversely, the colonization resistance of E. coli can only be exerted in highly diverse groups.
In addition to E. coli, researchers have also identified other colonization-resistant key bacteria, such as Bifidobacterium brevis, Phocaeicola vulgatus, and Lacrimispora saccharolyticum.
Hero units + people = high combat effectiveness
In this way, colonization resistance is actually a complex ecological problem, but interestingly, complex problems can be solved by simple principles.
The researchers analyzed the degree of overlap between the expressed protein and the use of carbon source and the pathogen in these strains, and found that the higher the overlap, the stronger the colonization resistance of the strains.
Using this rule, the researchers also tried to find the composition of the microbiota that can fight antimicrobial resistance (AMR) E. coli. Escherichia coli (AMR) has been the main target of antibiotic-resistant bacteria research in recent years, and it has become the number one killer of antibiotic resistance-related deaths.
Predict specific defense bacteria against specific pathogens
The researchers say these findings could drive new treatments, such as fighting harmful intestinal pathogens by optimizing the composition of intestinal bacteria. This could also explain why some individuals are more susceptible to pathogens such as Klebsiella pneumoniae after antibiotic treatment, as antibiotics reduce the diversity of intestinal bacteria.
Resources:
[1]https://www.science.org/doi/10.1126/science.adj3502
[2]https://www.eurekalert.org/news-releases/1010603
The author of this article丨 Dai Siyu