Bacterial DNA in Human Genomes | The Scientist Magazine®

Bacterial DNA in Human Genomes | The Scientist Magazine®.

Bacterial DNA in Human Genomes | The Scientist Magazine®

 

Image credit: Pseudomonas, one of the bacteria groups that have transferred genes to humans. CDC, JANICE HANEY CARR

 

One of the concepts we talk about late in the term is horizontal gene transfer.  Basically, this is the acquisition of DNA or genes from organisms other than your parents (or immediate line of descent).  It’s the equivalent of being able to absorb genes from other organisms.

 

And it doesn’t work in humans.

 

Okay, so, E. coli can scavenge genes from its environment.  If you leave a piece of DNA sitting on the petri dish gel, the bacteria can just pick it up, and voila, they have resistance.  Humans can’t do this; we don’t get flu genes into our DNA just because we touched a contaminated doorknob (thank goodness).  This is called lateral or horizontal gene transfer.

 

However, our DNA does have lots of bits from pathogens like viruses.  Viruses get inside the cell, so it’s easier for our cells to mistakenly pick up bits of their DNA, thinking that it’s our own.  That means it’s also plausible that our DNA can accumulate genes from other intracellular pathogens, such as mycoplasma bacteria, malaria, and maybe others.  In fact, our DNA shows that mitochondrial DNA genes have leaked in, and in plants, chloroplast genes jump from the chloroplast to the host cell.

 

What’s different about this work is that Pseudomonas is not an intracellular pathogen, but researchers have found genes from Pseudomonas and other bacteria embedded in human DNA.  In particular, these genes seemed to be more common in cancerous cells and other cells that divide rapidly.

 

Yet it’s not widely accepted at this time.  I think it makes sense. Cancer cells are known for their high mutation rate.  The mechanisms that proofread and spell-check their DNA are notoriously lousy at the job–which is partially why cancer cells are so messed up.  To me, it stands to reason that cells with poor error-checking capacity would be less likely to notice the intrusion of foreign DNA.

One Comment Add yours

  1. Jamie says:

    I agree with the idea you stated that cancer cells mutate at such a high rate. We still don't know so much about the human body, and who's to say the the cells that mutate into cancer don't carry pseudomonas they have become embedded in our DNA. There are certain things that cells do miss on occasion, and missing a DNA strand with the foreign bacteria might be accidentally over looked at some point. Nothing is perfect so there is still a chance for this to occur.

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