Back to Shapiro (Evolution)

by David Turell @, Thursday, April 08, 2021, 15:41 (35 days ago) @ dhw

A new study shows how bacteria can revive pseudogenes when necessary:

"The Technical University of Denmark has developed a method that speeds up evolution by pressuring bacteria and fungi to develop at a furious pace.

"Researchers have now discovered that this method – adaptive laboratory evolution – can also revive pseudogenes.

"The discovery is interesting because it indicates why evolution has retained these zombie genes that could otherwise easily have been discarded. The pseudogenes probably function like spare parts that keep an old car working so it can be used when the new one has broken down.


"A pseudogene is a gene that no longer functions and has shared ancestry with a functioning gene. For example, in evolutionary terms a bacterium may no longer require a specific protein coded by a specific gene and because this protein is not required for the organism to survive, the gene does not need to be repaired.

"The pseudogenes are a legacy in the genome from a time when the bacteria functioned differently. Bacteria have up to 10,000 genes and also between 100 and 1000 pseudogenes that have no function and appear not to have any purpose.

"The pseudogenes might be expected to disappear over time, but bacteria seem to retain them, which has long puzzled researchers.

"They finally have an idea why the bacteria do not discard the pseudogenes.


"The researchers investigated what happens to Escherichia coli if they gradually remove parts of the genes the bacterium uses to make proteins that draw iron into the bacterial cells.

"When bacteria enter a host, they need iron to divide and proliferate, and they absorb the iron from their surroundings using specific proteins. When these proteins no longer function, the bacteria stop growing and dividing.


"However, the researchers were also surprised to see that one of the bacterial cultures suddenly began to grow again, as if it still had fully functional versions of the genes the researchers had removed.

"The researchers analysed the genome of the bacteria and discovered that the bacteria still lacked the gene that had been removed. Instead the bacteria had repaired a pseudogene, which caused the bacteria to produce a different protein that could enable the cells to absorb iron.

“'The bacteria repaired a pseudogene that they were not using anymore. It was a minor repair. The bacteria needed to either remove two nucleotides from the DNA or insert four to activate the gene.


"After the researchers discovered the repaired pseudogenes, they returned to their database of 300,000 bacterial genomes to see whether any of the bacteria with which they previously had worked had also recreated lost functions by repairing pseudogenes. Here they found several other examples of bacteria that had taken old genes into use to survive.

“'This provides fascinating insight into how evolution works. Organisms do not seem to discard pseudogenes because they provide opportunities to survive. This is a genetic reservoir that they can use if needed."

Comment: Shapiro did excellent work and this study is further proof of his point that bacteria edit their DNA.

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