Bacterial antibiotic resistance: mechanism explained (Introduction)

by David Turell , Saturday, June 17, 2017, 22:32 (2497 days ago) @ David Turell

Bacteria that produce antibiotics carry naturally protective genes:

https://www.sciencedaily.com/releases/2017/06/170616102117.htm

"Now, research conducted at The Novo Nordisk Foundation Center for Biosustainability -- DTU Biosustain -- at Technical University of Denmark for the very first time shows that antibiotic resistance genes originate from the same place as the antibiotic compounds, i.e. from a group of soil bacteria called Actinobacteria.

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"More than three fourths of all current antibiotics used to treat human infections are produced by Actinobacteria, which at the same time carry antibiotic resistance genes.

"In these experiments, the researchers surprisingly found that many resistance genes in disease-causing microbes (gram negative pathogens) were very similar to resistance genes found in Actinobacteria. Especially in one case, the genes were 100% identical.

"It has been suspected that pathogens can obtain resistance genes from Actinobacteria for half a century. So now with the 100 % identical genes we find the smoking gun," says Postdoc Xinglin Jiang from DTU Biosustain.

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"But by investigating the DNA sequence around the resistance genes, the team figured out how the resistance genes transfer occurred through a new mechanism named "carry back," where the pathogen basically has a primitive form of "sex" with the Actinobacterium and takes up its resistance genes after it dies.

"This gene transfer by carry back could in principle happen where pathogens come into contact with Actinobacteria, like in an animal farm or in soil polluted with untreated hospital waste. In this way, the pathogen can become resistant and endanger human lives in the next round of infection.

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"By following the DNA-transfer, scientists for the very first time showed an unknown mechanism called carry back in which pathogens were able to snatch genes from far-related bacteria via the carry back mechanism. Here is how, in short, the carry back process works:

"1. The Gram negative pathogen injects its DNA into the Actinobacteria. Gram negative bacteria naturally have an ability called conjugation by which bacterial cells can inject their own DNA into other bacterial cells. It is called the bacterial equivalent of sex, because it is usually used to exchange gene information between Gram negative bacteria. But sometimes Gram negative bacteria can also use this mechanism to inject DNA into far-related Gram positive bacteria like Actinobacteria.

"2. Inside the Actinobacteria, the injected DNA recombines with the host's DNA containing resistance genes. After the Actinobacterium dies, the recombinant DNA is released into the environment.

"3. Lastly, the injected DNA can act as "gluing DNA" and mediate the uptake of resistance gene back to the pathogens through a phenomenon called natural transformation."

Comment: this is an expected finding. Bacterial wars go on and they carry defense mechanisms which they can use automatically. Survival doesn't take intelligence. Just pick up the protective genes. Bacteria have been around since the start of life 3.8 billion years ago. This is one reason why.