WWW.NATURE.COM/NATURE
VOL.437 NO.7060 DATED 06 OCTOBER 2005
* Biomimetics: Teaching blood cells to swim
* Astrophysics: Short gamma-ray bursts pinned down
* Ecology: How fish in a pond control terrestrial plants
* Animal behaviour: Honeybees take advantage of anarchy
* Earth sciences: Molecular fossils offer insights into the marine ecosystem on early Earth
* Earth science: How earthquakes trigger distant tremors
* Cell biology: Fungus lets bacterial subtenant do the work
* Neurobiology: The staying power of neural stem cells
* And finally... Male tears have sex appeal
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[1] Biomimetics: Teaching blood cells to swim (pp 862-865)
A red blood cell has been turned into a microscopic swimmer, as reported in
this week's issue of Nature. The researchers have attached a synthetic,
magnetically controlled tail to cells so that they become able to wiggle
through liquid in a manner reminiscent of spermatozoa, although the
artificial structures described here swim backwards, in the direction of the
free end of the tail.
Remi Dreyfus and colleagues constructed these tails from magnetic spheres
just one micrometre (a thousandth of a millimetre) across. They linked
several spheres into chains about 30 micrometres long by bridging them with
strands of DNA, primed to stick to the spheres at each end. The team then
grafted the chains at one end onto human red blood cells.
The tail aligns with an external magnetic field that can be adjusted to
control the speed and direction of motion. By applyinga transverse
oscillating magnetic field, the tails move from side to side and also bend,
owing to the viscous drag of the solvent. The resulting wiggle-propulsion
echoes the way that some bacteria move by waving filamentary appendages
called flagella. The researchers say that their process could be used for
placing micro-objects (in this case, the red blood cell) in precisely
controlled positions.
CONTACTS
Remi Dreyfus (Ecole Supérieure de Physique et de Chimie Industrielles,
Paris, France)
Tel: +33 1 40 79 52 00; E-mail: [email protected]
[2] - [5] Astrophysics: Short gamma-ray bursts pinned down (pp 845-861; N&V)
Intense explosions are generated when compact objects such as neutron stars
or black holes merge together, according to four research papers published
in this week's Nature.
Long gamma-ray bursts, lasting more than a few seconds, are released when
the cores of young, massive stars collapse. But the origin of their shorter
counterparts had remained a mystery. The HETE-II and Swift satellites have
now localized two bursts, allowing ground-based observers to find the
galaxies hosting the bursts, and to find the fading optical signature of one
of them.
Neil Gehrels and colleagues detail the X-ray afterglow from a short burst
seen on 5 May this year, and found that it seemed to be coming from a
distant elliptical galaxy containing older stars, although there was no
optical counterpart to the burst.
Joel Villesenor and colleagues report that a second short burst was spotted
on 7 July by HETE-II, and its X-ray afterglow was detailed by Dale Frail and
colleagues. The event also provided the first sighting of an optical
afterglow from a short gamma-ray burst, described by Jens Hjorth and
colleagues.
The researchers show that these short bursts are about a thousand times less
luminous than those produced by long gamma-ray bursts, consistent with
theoretical predictions for a sudden collision between dense objects. By
measuring the energy output of the explosion, the scientists also rule out
alternative sources such as flares from highly magnetized neutron stars.
"The observed characteristics of the short gamma-ray bursts are all
consistent with models of the merger of two neutron stars, or of a neutron
star with a black hole," comments Luigi Piro in a related News and Views
article.
CONTACTS
Dale Frail (National Radio Astronomy Observatory, Socorro, NM, USA)
Tel: +1 505 835 7338; E-mail: [email protected] Paper [2]
Neil Gehrels (NASA Goddard Spaceflight Center, Greenbelt, MD, USA)
Tel: +1 301 286 3106; E-mail: [email protected]
<mailto:[email protected]> Paper [3]
George Ricker (Massachusetts Institute of Technology, Cambridge, MA, USA)
Tel: +1 617 253 7532, E-mail: [email protected] Paper [4]
Jens Hjorth (University of Copenhagen, Denmark)
Tel: +45 35 325 928; E-mail: [email protected] Paper [5]
Luigi Piro (Instituto Astrofisica Spaziale, Roma, Italy)
Tel: +39 6 4993 4007; E-mail: [email protected]
<mailto:[email protected]> News and Views author
[7] Ecology: How fish in a pond control terrestrial plants (pp 880-883)
Land and water ecosystems could exert a greater influence on one another
than previously thought. A study of pond ecology in a natural sanctuary in
Florida, appearing in this week's Nature, shows how species interactions can
have consequences that spill over from one habitat to another. Tiffany
Knight and her team looked at eight ponds in the sanctuary, four of which
contained predatory fish that eat dragonfly larvae.
The scientists found that plants near the ponds containing these fish fared
better than those around fish-free ponds. But what caused this benefit to
the plants? By eating the dragonfly larvae, the fish appear to reduce the
populations of adult dragonflies that would normally feed on insect
pollinators of the terrestrial plants, Knight and her colleagues explain.
With more dragonflies out of the picture, the pollinating insects can thrive
and promote a flourishing land ecosystem.
CONTACTS
Tiffany Knight (Washington University in St. Louis, MO, USA)
Tel: +1 314 935 5678; E-mail: [email protected]
[8] Animal behaviour: Honeybees take advantage of anarchy (p 829)
When a society loses its leadership, it can be vulnerable to exploitation by
infiltrators from outside. That's certainly the case for Asian dwarf red
honeybees (Apis florea) - when a queen dies, workers from other colonies
take advantage of the ensuing lawlessness by laying eggs in the queenless
nest, safe in the knowledge that they will not be killed.
On the death of the queen, some native workers within the nest abandon their
usual duties of policing the colony's reproductive activities and begin to
reproduce themselves, and raise one final generation before the group dies
out. And that's when non-native workers from rival colonies can seize the
initiative, report Benjamin Oldroyd and his colleagues in a Brief
Communication in this week's Nature.
The researchers removed the queens from honeybee colonies, and found that
the proportion of non-native workers jumped from around 2% to 4.5%. Of
these, almost half had active ovaries, compared with around 18% of native
workers. The authors add that such parasitism is not seen in colonies of
western honeybees (Apis mellifera), probably because these bees live in
closed-off nests, as opposed to the open nests inhabited by the Asian bees.
CONTACTS
Benjamin P. Oldroyd (University of Sydney, Australia)
Tel: +61 2 9351 7501; E-mail: [email protected]
[9] Earth sciences: Molecular fossils offer insights into the marine
ecosystem on early Earth (pp 866-870; N&V)
Molecular fossils of sulphur bacteria support the idea of a mostly
oxygen-depleted, sulphur-rich ocean around 1,800 to 800 million years ago,
according to scientists reporting in this week's Nature.
Rising oxygen levels mark the end of a 2.5-billion-year-long period
dominated by oceans deprived of oxygen. On the basis of geochemical
evidence, it is generally thought that despite increased oxygen
concentrations in the ensuing mid-Proterozoic era - 1,800 to 800 million
years ago - the oceans remained sulphidic and largely devoid of oxygen.
These conditions are believed to be unfavourable to many forms of life.
Jochen Brocks and colleagues have now discovered molecular fossils, or
hydrocarbon biomarkers, in 1.6-billion-year-old sedimentary rocks from a
marine basin in northern Australia. These fossils hold vital clues into the
marine ecosystem at the time.
The authors find that the biomarkers record an anoxic (oxygen-deficient) and
sulphidic world hostile to oxygen-producing algae, but supporting blooms of
sulphide-breathing green and purple bacteria. Until now, these bacteria had
not been seen in the geological record.
Collectively, the molecular fossils provide biological evidence for a
Proterozoic world in which oxygen levels remained well below those of the
modern ocean.
CONTACTS
Jochen Brocks (Australian National University, Canberra, Australia)
Tel: +61 2 6125 7946; E-mail: [email protected]
David Des Marais (NASA/Ames Research Center, Moffett Field, CA, USA)
Tel: +1 650 604 3220; E-mail: [email protected]
<mailto:[email protected]>
[10] & [11] Earth science: How earthquakes trigger distant tremors (pp
871-874 & 830)
Two papers in this week's Nature describe how earthquakes can trigger
additional quakes at remote distances.
Although the effect has been dramatically observed in events such as the
1992 magnitude 7.3 Landers earthquake in California, geologists do not
understand how such remote triggering works.
To model this triggering in the laboratory, Paul A. Johnson and Xiaoping Jia
observed waves travelling through glass beads held under pressure. Their
results suggest that remote earthquake triggering is the result of seismic
waves impinging on a fault and inducing surprisingly large weakening of the
ground-up material in the core of the fault, known as the fault gouge. They
found that even though the strain produced by seismic waves diminishes
rapidly as it travels far away from the main earthquake, it is still
sufficient to cause the gouge material in faults to weaken enough to trigger
additional quakes.
In a related Brief Communication, Joan Gomberg and Paul Johnson confirm that
the glass bead model is a good analogue for real earthquakes. They compare
data from a range of remotely triggered events and find that the most
important triggering factor is the amplitude of the seismic waves and not
their frequency, which matches the behaviour of the granular material
studied in the laboratory by Johnson and Jia.
CONTACT
Paul Johnson (Los Alamos National Laboratory, NM, USA. Currently at:
Université de Marne-la-Vallée, France)
Tel: +33 1 60 95 72 37; E-mail: [email protected]
Joan Gomberg (US Geological Survey, Memphis, TN, USA)
Tel: +1 901 678 4858; E-mail: [email protected] <mailto:[email protected]>
[12] Cell biology: Fungus lets bacterial subtenant do the work 884-888; N&V)
Researchers have identified bacteria that live inside the cells of a fungus
to help the fungus produce a substance their host needs, a process called
endosymbiosis. The fungus, which infects rice plants, uses a substance
called rhizoxin to keep the rice cells from dividing. Eventually, this
infection can kill the rice plant, and both - the fungus and the bacteria -
profit from the nutrients they get when the dying rice plant decays.
Laila Partida-Martinez and Christian Hertweck first looked in the fungus to
identify the gene for the enzyme that produces rhizoxin. To their surprise,
they couldn't find a fungal gene, they report in this week's Nature.
Instead, they found a bacterial version of the gene, suggesting that the
fungal cells harbour bacteria that produce the enzyme for them.
Indeed, they found the bacteria when they took a look with a microscope, and
showed that the bacteria can even make rhizoxin when kept outside the
fungus, albeit only for a limited time. The fungus probably produces signals
that make the bacteria produce the chemical as long as they are inside the
fungal cell, they speculate.
Next, the researchers want to identify the bacterial genes that are involved
in the synthesis of rhizoxin, which is a candidate for an anti-tumour drug
because it inhibits cell division.
CONTACT
Christian Hertweck (Leibniz Institute for Natural Products Research and
Infection Biology, Jena, Germany)
Tel: +49 36 4165 6701; E-mail: [email protected]
Ian R. Sanders (University of Lausanne, Switzerland)
Tel: + 41 21 692 4261; E-mail: [email protected]
<mailto:[email protected]>
[13] Neurobiology: The staying power of neural stem cells (pp 894-897)
Neural stem cells in the brain are able to self-renew for over a year, a
study in mice has found. They are also able to produce several different
types of nerve and glial cells, according to a Letter in this week's Nature.
Sohyun Ahn and Alexandra Joyner used a genetic technique to permanently
label those cells in the adult mouse brain that respond to a signal called
Sonic hedgehog (Shh), which triggers cell division in many cell types.
Labelled cells and their progeny turn permanently blue if they receive a Shh
signal at a certain time, making them easy to identify and track over time.
The authors labelled neural stem cells in the quiescent stage (that is, in a
resting state), before they begin to divide and develop into later-stage
stem cells with shorter lifespans. Both the small population of resting stem
cells and the more rapidly dividing, later-stage stem cells respond directly
to the Shh signal, the researchers report.
What's more, the stem cells develop into several different kinds of nerve
and glial cells. Resting stem cells were still able to start dividing and
develop into different cell types one year after labelling. This long-term
self-renewal of stem cells might also happen in humans, the authors say.
CONTACT
Alexandra Joyner (New York University School of Medicine, NY, USA)
Tel: +1 212 263 7290, E-mail: [email protected]
[14] And finally... Male tears have sex appeal (pp 898-901)
Pheromones - chemicals that can function to send signals to the opposite sex
- often waft over long distances from one animal to another. Butterflies,
for example, use pheromones to attract mates that can be miles away. But a
paper in this week's Nature describes a non-volatile pheromone in mice that
is secreted from the eyes and transmitted by direct contact.
We already know that rodents respond to volatile compounds in urine, and
behavioural studies now suggest an additional method of pheromonal
communication. Kazushige Touhara and colleagues show that sex-specific
peptides from the eye glands of male mice reach and attract female mice
through direct physical contact. This finding opens a new avenue for
understanding sexual communication and gender discrimination in mammals.
CONTACT
Kazushige Touhara (The University of Tokyo, Chiba, Japan)
Tel: +81 471 36 3624; E-mail: [email protected]
ALSO IN THIS ISSUE...
[15] Structure of the CED-4-CED-9 complex provides insights into
programmed cell death in Caenorhabditis elegans (pp 831-837)
[16] STIM1 is a Ca21 sensor that activates CRAC channels and migrates
from the Ca21 store to the plasma membrane (pp 902-905)
[17] Apolipoprotein-mediated pathways of lipid antigen presentation (pp
906-910)
[18] Chaperone release and unfolding of substrates in type III secretion
(pp 911-915; N&V)
[19] Direct observation of steps in rotation of the bacterial flagellar
motor (pp 916-919)
GEOGRAPHICAL LISTING OF AUTHORS...
The following list of places refers to the whereabouts of authors on the
papers numbered in this release. For example, London: 4 - this means that
on paper number four, there will be at least one author affiliated to an
institute or company in London. The listing may be for an author's main
affiliation, or for a place where they are working temporarily. Please see
the PDF of the paper for full details.
AUSTRALIA
Canberra: 9
Sydney: 8, 9
Weston Creek: 2
BRAZIL
Rio de Janeiro: 6
Sao Jose dos Campos: 4
CANADA
Toronto: 2
CHILE
Santiago: 5
DENMARK
Copenhagen: 2, 3, 5
FRANCE
Marne la Vallee: 10
Paris: 1
Toulouse: 4
GERMANY
Jena: 12
Tautenburg: 3
INDIA
Mumbai: 4
ISRAEL
Jerusalem: 2
ITALY
Bologna: 4
Frascati: 3
Merate: 3
Milan: 3
Palermo: 3
JAPAN
Kanagawa: 3
Kyoto: 2
MiyazakiL 4
Nagoya: 19
Sagamihara: 4
Saitama: 19
Sakura: 3
Tokyo: 2, 4, 14
Tsukuba: 4
REPUBLIC OF KOREA
Gwangju: 15
THE NETHERLANDS
Amsterdam: 3
SPAIN
Granada: 5
SWEDEN
Stockholm: 3, 5
THAILAND
Bangkok: 8
Mahasarakham: 8
UNITED KINGDOM
Aberdeen: 9
Birmingham: 17
Dorking: 3
Leicester: 3
Oxford: 19
UNITED STATES OF AMERICA
Alabama
Huntsville: 3, 5
California
Berkeley: 2, 3, 4
Claremont: 2
Irvine: 16
La Jolla: 16
Livermore: 2
Pasadena: 2
Rohnert Park: 3
Santa Cruz: 4
Colorado
Boulder: 15
Pine: 4
Connecticut
New Haven: 18
District of Columbia
Washington: 3
Florida
Gainesville: 7
Hawaii
Hilo: 2
Honolulu: 2, 5
Illinois
Chicago: 4
Maryland
Baltimore: 3
Bethesda: 13
College Park: 3
Columbia: 3
Greenbelt: 3, 4
Massachusetts
Boston: 17
Cambridge: 1, 4, 9
Hull: 4
Missouri
St. Louis: 7
New Jersey
Princeton: 2, 15
New Mexico
Los Alamos: 3, 4, 10, 11
Socorro: 2
Nevada
Las Vegas: 3
New York
Ithaca: 15
New York: 13
Upton: 15
Pennsylvania
University Park: 2, 3
Tennessee
Memphis: 11
Texas
Austin: 2
Virginia
Charlottesville: 2, 3
PRESS CONTACTS...
For North America and Canada
Katie McGoldrick, Nature Washington
Tel: +1 202 737 2355; E-mail: [email protected]
<mailto:[email protected]>
For Japan, Korea, China, Singapore and Taiwan
Rinoko Asami, Nature Tokyo
Tel: +81 3 3267 8751; E-mail: [email protected]
<mailto:[email protected]>
For the UK/Europe/other countries not listed above
Ruth Francis, Nature London
Tel: +44 20 7843 4562; E-mail [email protected]
<mailto:[email protected]>
Katharine Mansell, Nature London
Tel: +44 20 7843 4658; E-mail: [email protected]
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Fax: + 44 207 843 4951
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