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Bacteria make viruses to distribute DNA

Sun, 3rd Oct 2010

There are clear benefits to society of sharing resources, which, for certain microorganisms, can include sharing your genes. Now scientists have shown that some bacteria assemble their own virus-like particles to boost the efficiency, more than a Influenza Virusmillion-fold, of the spread of their genetic "know how" throughout the microbiological community.

The existence of GTAs - or gene transfer agents, tiny virus-sized particles containing chunks of bacterial genetic material - had been documented previously (in 1974), but the significance of their contribution to the spread of advantageous genetic traits amongst microbes had never been determined.

To establish their role, University of South Florida scientist Lauren McDaniel and her colleagues, writing in Science, cultured a strain of reef-dwelling bacterium called Rhodobacter capsulatus known to produce GTAs.

Using genetic engineering techniques, she added to these bugs genes conferring resistance to several antibiotics. Then, either by growing these modified bugs alongside other previously non-antiobiotic resistant bacteria, or by adding just the GTAs collected from the modified bacteria, she was able to demonstrate that up to 47% of the formerly antibiotic-sensitive bacteria became antibiotic resistant.

The results show that these bacterial virus-like particles are a highly efficient vehicle for the transmission of genetic traits amongst a range of microbes, and, according to the researchers "suggest a genomic flexibility in marine microbial populations that facilitates their adaptation to changing environmental conditions. are a powerful means by which microbes adapt to changing environments."

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For bacteria, sex and procreation are separate activities. SteveFish, Sun, 10th Oct 2010

Hi Steve

that's an interesting point - can you elaborate on it please?

Chris chris, Sun, 10th Oct 2010

Having an appendage long enough to walk on would impress most men I think...

http://sciencenews.org/view/generic/id/64083/title/Bacteria_strut_their_stuff#video

Awww cute!


Good article though, I would be interested to know how stable GTA's are and what the genes responsible for GTA production and regulation are. Chris do you know much about GTA's? Variola, Sun, 10th Oct 2010

Chris:

That prokaryotes transfer DNA between individuals by viruses and plasmids is not new information. Further, there are recognized DNA sequences even in eukaryotes, including humans, that are obviously derived from viruses, but this is a very low probability event. We eukaryotes generally have sex to exchange DNA and this is coupled to reproduction by creating new individuals with a combination of the two parent gene sets.

Prokaryotes reproduce by cell division which produces two new individuals identical to the parent cell (unless there is a mutation). But, prokaryotes also exchange genetic information (have sex, e.g. by viruses/plasmids) and this process is independent of reproduction. This method would seem to be a bit haphazard, but when you can create a gazillion (technical term) offspring in a few days, efficiency is not very important.

Here is the scary part. Prokaryotes don't have to be the same species, like we eukaryotes, in order to exchange DNA. Agribusiness utilizes a variety of antibacterials that are applied prophylactically to improve meat/egg/milk production. This is just the right regimen for creating antibacterial resistant bacteria, and because bacteria of different species have sex, the bacterial resistance can be transferred to a bacteria that attacks many different eukaryote species, including humans. Are you wondering where all of the antibacterial tolerant nasties come from?

This fascinating topic is covered in many of the new cell and molecular biology courses that have been popping up at universities. You can also pick up an older (reduces cost) Alberts et.al., Molecular Biology of the Cell text to get more technical information (this is a graduate level text). And, I seem to recall from distant memory, that Lynn Margules wrote a popular book that covered this topic, among others. Possibly-- Margulis, Lynn and Dorian Sagan, 1997, What Is Sex?, Simon and Shuster, ISBN 0-684-82691-7.

Steve  SteveFish, Mon, 11th Oct 2010

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