Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bugs enjoy hamster sex

19.11.2001


Bacteria mate using a timely protruding phallus.
© SPL


Mammalian cells rarely take bacteria up on their offer of DNA.
© Photodisc


Bacteria caught mating with mammalian cells.

Cross-species coupling is generally frowned upon. But in the liberal labs of California it is actively being encouraged. Bugs that are persuaded to get down and dirty with hamster cells are rewriting sex manuals in the act.

Like humans, bacteria mate using a timely protruding phallus. It suckers a nearby bacterium and drags it close enough to shoot in DNA - a process called conjugation.



Although bacteria have been persuaded in the past to share DNA with plants and yeast, they had never been caught at it with mammalian cells before. For Virginia Waters of the University of California, San Diego, persistence paid off. She laid Escherichia coli on top of hamster cells and allowed them to get intimate: "You leave them overnight," she says.

Waters showed the bacteria had transferred DNA by tracking a gene that makes green fluorescent protein. Post-coital hamster cells literally light up1.

Free and easy

For years bacteria were assumed to be picky about their partners, says George Sprague of the University of Oregon in Eugene. Their surfaces were thought to be too dissimilar to get close to other cells. "People had a mindset that this was something bacteria enjoyed with each other," he says.

The soil bacterium Agrobacterium tumefaciens regularly indulges with plants cells, it later emerged. And in 1989, Sprague showed bacteria’s willingness to try it on with yeast2. "It was a surprise to the scientific community," he says. Pairing up bacteria with mammalian cells "seemed like the ultimate sexy experiment".

The secret to a fertile union lies in carefully detecting the rare deviants, thinks Waters - only around 1 in 10,000 mammalian cells. She also engineered the promiscuous bacteria to contain circular DNA (a plasmid) that could survive and replicate in the recipient hamster cell.

Waters’s results suggest that bacteria try their luck with mammalian cells all the time. But there is little evidence that such matings are fruitful - reports of bacterial genes transferred directly into the human genome are disputed3,4.

Bacteria commonly conjugate to exchange survival genes, such as those that confer antibiotic resistance. But for a gene to jump permanently into a mammalian genome it would have to be transferred from bacteria into a sperm or egg, integrated into its genome and passed on to the next generation.

Although this is possible, it is probably very rare, suggests Jean-Marc Ghigo, who studies conjugation at the Pasteur Institute in Paris. And unlike the engineered DNA used in Waters’s experiment, wild bacterial DNA may be degraded by the recipient cell - an innate prophylactic.

Sex therapy

Waters hopes to exploit bacteria’s wanton ways for gene therapy - the transfer of healthy genes into human cells to compensate for defective ones causing disease. In the lungs, for example, resident bacteria could be modified to carry and transfer genes such as the one that is faulty in the lung disease cystic fibrosis.

"It could be a powerful way to deliver DNA," agrees Ghigo. Large populations of bacteria constantly attempting sex might have more success than a single dose of another gene-delivery drug.

Gene-therapy researcher Stephen Hyde at the University of Oxford, UK, is more doubtful. Thick protective mucous might stop the bacteria getting close to lung cells, he points out. Introducing bacteria into the body and transferring unwanted bacterial genes might also be risks.

In the lab, conjugation could be a way to transfer large pieces of DNA into mammalian cells. Such transfers are currently difficult, says Hyde, as the DNA tends to break easily.

Fertility aside

Conjugation was first reported in 1946, winning its voyeur, Joshua Lederberg, a Nobel prize. The plasmid that carries the genes responsible was named the fertility factor.

The transfer of circular DNA always starts at a defined point. By interrupting mating bugs at regular intervals, geneticists were able to work out which genes had been passed over. Hence the first map of the E.coli chromosome was measured in minutes rather than megabases.

References

  1. Waters, V. L.Conjugation between bacterial and mammalian cells. Nature Genetics, DOI: 10.1038/ng779 (2001).
  2. Heinemann, J. A. & Sprague, G. F. Bacterial conjugative plasmids mobilize DNA transfer between bacteria and yeast. Nature, 340, 205 - 209, (1989).
  3. Salzberg, S. L., White, O., Peterson, A. J. & Eisen, J. A.. Micorobial genes in the human genome: lateral transfer or gene loss? Science, 292, 1903 - 1906, (2001).
  4. Stanhope, M. J. et al. Phylogenetic analyses do not support horizontal gene transfers from bacteria to vertebrates. Nature, 411, 940 - 944, (2001).


HELEN PEARSON | Nature News Service
Further information:
http://www.nature.com/nsu/011122/011122-4.html

More articles from Life Sciences:

nachricht A room with a view - or how cultural differences matter in room size perception
25.04.2017 | Max-Planck-Institut für biologische Kybernetik

nachricht Studying a catalyst for blood cancers
25.04.2017 | University of Miami Miller School of Medicine

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Early organic carbon got deep burial in mantle

25.04.2017 | Earth Sciences

A room with a view - or how cultural differences matter in room size perception

25.04.2017 | Life Sciences

Warm winds: New insight into what weakens Antarctic ice shelves

25.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>