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 Solving the efficiency of Gram-negative bacteria
22.03.2019 | Harvard University

nachricht Bacteria bide their time when antibiotics attack
22.03.2019 | Rice University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: The taming of the light screw

DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.

The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...

Im Focus: Magnetic micro-boats

Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.

The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...

Im Focus: Self-healing coating made of corn starch makes small scratches disappear through heat

Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.

Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...

Im Focus: Stellar cartography

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...

Im Focus: Heading towards a tsunami of light

Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.

"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

Solving the efficiency of Gram-negative bacteria

22.03.2019 | Life Sciences

Bacteria bide their time when antibiotics attack

22.03.2019 | Life Sciences

Open source software helps researchers extract key insights from huge sensor datasets

22.03.2019 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>