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 Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>