The gut microbiome is very diverse, and the microorganisms do not live in harmony
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Your gut is a battlefield where Rival bacterial tribes armed with poisonous darts fight for territory – and these battles are usually won by armies of traitors switching sides through the selfish DNA transferred by their enemies.
“The human colon is one of the densest microbial ecosystems on Earth,” he says Laurie Comstock at the University of Illinois at Chicago. There are many species of bacteria, and different strains within species, fighting for the same resources.
To gain the upper hand, many release toxins in an attempt to poison their rivals. Some are armed with an even more extraordinary weapon: dart guns that shoot high-velocity syringes. to inject poisons directly into other bacteria or larger nearby cells.
“They’re a spring-loaded weapon that requires organisms to be very close,” says Comstock.
The naive-sounding name for this type of dart gun is the Type 6 Release System, or T6SS. A wide range the species they are armed with them, and there are many variations in the way they operate; darts can contain many different toxins, e.g.
But how do blind bacteria avoid shooting friends and even the enemy? They don’t have Some species shoot poison darts as fast as they can, hitting friends and foes alike.
Crucially, however, the genetic instructions for making a specific type of dart gun always come with the instructions for making an antidote to the poison in the darts fired by that gun. When a bacterium is struck by the darts of a member of its tribe, it does no harm.
In other words, in this world of poison darts and antidotes, which side is a bacterium on? it is determined what dart gun and antidote he manufactures.
In this world of bug-shooting bugs, it’s a species called one of the most vicious Bacteroides fragiliswhich releases a barrage of poison as well as firing its darts non-stop. B. fragilis it feeds on complex sugars found in the mucus lining of the intestines, so Comstock believes the reason for its attack is to try to grab the mucus lining and defend it against other related species.
But some of these other species have special weapons Bits of selfish DNA that act almost as independent entities. One of these pieces of DNA, called GA1, encodes the genes for the machinery that enables GA1 transferring copies of himself to other bacteria.
It also contains the dart gun genes and the antidote to the dart gun poison. This is what Comstock’s team has shown once GA1 is introduced B. fragilisit somehow blocks the production B. fragilis gun and starts producing the GA1 pistol, essentially turning him into a traitor.
When these bacteria they form treacherous armies that can multiply, kill B. fragilis Those lacking GA1. Treacherous armies tend to win these battles, Comstock’s team found in several tests.
But in our guts, where many other species and toxins are present, the results can be different, he says. “There are a lot of things to consider in these battles,” says Comstock. “There is not always a clear winner.”
His team has also discovered another selfish DNA called GA2, which appears to act similarly to GA1 but with a different dart gun and antidote.
“Lateral changes may be more common than we think,” he says Brian Hammer at the Georgia Institute of Technology in Atlanta.
Even the bacterium that causes cholera is constantly producing and firing dart guns. Although this behavior is believed to be expensive, last year Hammer’s team showed this tension Vibrio cholerae which do not produce T6SS faster than those that hardly growit suggests that the cost of walking around guns blazing is surprisingly low.
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