NATURE VOL.436 NO.7054 DATED 25 AUGUST 2005
* Neurobiology: Brain cells tune in to pitch
* Microbiology: Plants use bacteria to recycle carbon from methane
* Microbiology: Bacteria do much better when they collaborate
* Geology: Helium-3 - all is not lost
* Meteoritics: Who you jivin' with that cosmic debris?
* Structural biology: An action-packed history of muscle proteins
* Chemistry: Giving photochemistry a hand
* And finally... Solvent switching
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[1] Neurobiology: Brain cells tune in to pitch (pp1161-1165; N&V)
Our brains can recognize that two notes with different frequencies - middle
C and high C, for example - share the same pitch. So pitch perception can
remain constant despite large changes in the acoustical input. This
constancy is important for music appreciation and, importantly, speech
perception, but how the brain perceives pitch is unknown. Now, a study in
Nature from Daniel Bendor and Xiaoqin Wang describes neurons in the auditory
cortex whose activity may represent a neural correlate for the perception of
pitch.
The team found pitch-selective neurons in the brain of the marmoset
monkey that respond to different sounds sharing the same fundamental
frequency. Bendor and Wang also showed that these same neurons respond to
sound combinations that merely imply this fundamental frequency. The
experiments revealed that a neuron will respond to the missing fundamental
frequency even if the sound stimuli are outside of the range that normally
excites it.
"This property makes psychologists happy, because it provides
evidence - if not yet a mechanism - for perceptual constancy." explains
Robert Zatorre in a related News and Views piece.
CONTACT
Daniel Bendor (Johns Hopkins University School of Medicine, Baltimore, MD,
USA)
Tel: +1 410 502 6019; E-mail: [email protected]
Robert Zatorre (McGill University, Montreal, Canada)
Tel: +1 514 398 8903; E-mail: [email protected]
[2] Microbiology: Plants use bacteria to recycle carbon from methane
(pp1153-1156)
Scientists have identified a symbiotic relationship that may explain the
large amount of methane recycling - the second most important greenhouse gas
- in wetland ecosystems. Jaap S. Sinninghe Damste and colleagues show that
submerged Sphagnum mosses in peat bogs can consume methane through symbiosis
with certain bacteria.
The bacteria live inside the moss cells, the researchers report in this
week's Nature. They oxidize the peat decomposition product methane to carbon
dioxide, which the plant cells in turn use as a source for their cell
carbon.
The mosses - the dominant plants in wetlands - use this mechanism for about
15 per cent of their carbon intake, making this new type of symbiosis
perhaps as significant as the symbiosis of rhizobia with leguminous plants
for nitrogen fixation.
CONTACT
Jaap S. Sinninghe Damste (Royal Netherlands Institute for Sea Research
(NIOZ), Den Burg, The Netherlands)
Tel: +31 222 369 550; E-mail: [email protected]
[3] Microbiology: Bacteria do much better when they collaborate (1157-1160)
A species-rich community of bacteria does better at certain tasks than a
community with few species according to a Letter published in Nature this
week. Andrew K. Lilley and colleagues randomly collected bacteria from rain
pools in bark-lined depressions of European beech trees (Fagus sylvatica),
cultured them and determined the respiration rate of communities consisting
of up to 72 different bacterial species.
They found that respiration increased with increased species richness. This
finding could be relevant for those trying to use bacteria for services like
breaking down pollutants in contaminated soils.
However, the researchers caution that there is a long way to go before we
are able to use the entire range of bacterial diversity found in nature.
Natural ponds of water harbour several thousand different bacterial species,
many of which cannot yet be cultured. This obstacle needs to be overcome in
order to make full use of bacterial communities for ecologically useful
services.
CONTACT
Andrew K. Lilley (NERC Centre for Hydrology and Ecology, Oxford, UK)
Tel: +44 1865 281630; E-mail: [email protected]
[4] Geology: Helium-3 - all is not lost (pp1107-1112; N&V)
Is there a reservoir of primordial rock deep within the Earth, left over
from the birth of our planet? Geochemical data have traditionally indicated
'yes', but evidence from seismology seemed inconsistent with the survival of
such a reservoir. This week in Nature, Cornelia Class and Steven Goldstein
present a theory that may allow geologists to resolve this contradiction.
The question arose because the rocks of ocean islands like Hawaii contain
relatively large amounts of helium-3, an isotope that must be mainly left
over from the days when the Earth first formed, because it is not generated
from the radiogenic decay of other elements. Researchers believed that
helium-3-rich minerals should only come from untouched primordial rock that
has welled up from deep within the mantle and has not previously been
'degassed' when partially melted near the Earth's surface.
But seismologists look upon this evidence with dismay. They see no evidence
that large portions of the mantle have escaped the mixing and melting that
drives plate tectonics and makes volcanoes.
Class and Goldstein show that the other minerals in ocean island rocks tell
a different story - the most helium-3-rich rocks also contain elements that
resemble the composition of rock that has melted before, such as that found
at mid-ocean ridges. The best explanation for all this, they say, is simply
that the mantle loses less of its helium than expected during melting. Their
model, which will need physical experiments to back it up, explains how this
might happen. A News and Views article by William M. White accompanies this
research.
CONTACT
Cornelia Class (Columbia University, Palisades, NY, USA)
Tel: +1 914 365 8712; E-mail: [email protected]
William M. White (Cornell University, Ithaca, NY, USA)
Tel: +1 607 255 7466; E-mail: [email protected]
[5] Meteoritics: Who you jivin' with that cosmic debris? (pp1132-1135)
A team of researchers have seen the cloud of dust left behind by a meteor
that exploded as it entered the Earth's atmosphere. They argue in this
week's Nature that the grains are much larger than expected, and that such
explosions could be the main source of 'cosmic dust' that accumulates on the
Earth.
A meteoroid is a small chunk of rocky debris in the Solar System, ranging in
size from a boulder to a sand grain. When such objects enter the Earth's
atmosphere, they typically break up into tiny fragments at high altitude,
creating the blazing trails we call meteors or shooting stars. It has been
widely thought that the break-up produces grains just a few nanometres
across, which then stick together to make a kind of meteoric 'smoke'.
A large meteor was spotted by satellites on 3 September 2004, which left a
bright trail stretching across altitudes from 56 to 18 km. Observations
suggested that the object originally had a mass of about a million kilograms
and that its break-up released an energy equivalent to 13-28 kilotons of TNT
- at least as much as the nuclear bomb that destroyed Hiroshima in 1945.
Andrew Klekociuk and colleagues have studied the 'cloud' that was detected
in the upper stratosphere in the wake of the meteor, made up of the dust
particles produced in the explosion. They find that these particles are as
large as 10-20 micrometres. Such grains will rain down from the atmosphere
over the course of several weeks, and the researchers say that they might
have an effect on our planet's climate, both by reflecting sunlight and by
encouraging cloud water droplets to form.
CONTACT
Andrew Klekociuk (Australian Antarctic Division in Kingston, Tasmania,
Australia)
Tel: + 61 362 323 382; E-mail: [email protected]
[6] Structural biology: An action-packed history of muscle proteins
(pp1113-1118; N&V)
Inside the cells of many organisms reside special motor proteins known as
myosin that use chemical energy to move structural filaments within the
cell. This process is at the heart of muscle contraction, as well as cell
migration. But how did myosin come to have this function? A new study
appearing in Nature helps to answer this question.
Thomas Richards and Thomas Cavalier-Smith offer the most
comprehensive evolutionary analysis of myosin to date. The authors based
their report on 23 complete or near-complete genomes. Their work uncovered a
rich variety of myosins throughout the eukaryotes - organisms that have
nuclei - including plants and animals. The paper catalogues 37 distinct
types of myosin - almost doubling the number of previously known ones.
"Comparison of these properties will provide more information about
the conservation and diversity of motor function in a range of different
cellular contexts," Margaret Titus writes in a related News and Views
article.
CONTACT
Thomas Richards (currently at: University of Exeter, UK)
Tel: +44 1392 264689; E-mail: [email protected]
Margaret Titus (University of Minnesota, Minneapolis, MN, USA)
Tel: +1 612 625 8498; E-mail: [email protected]
[7] Chemistry: Giving photochemistry a hand (pp1139-1140; N&V)
Making molecules with the right handedness - either a left- or a
right-handed arrangement of atomic groupings - is of critical importance to
the pharmaceutical industry, as the two different 'handed' forms (called
enantiomers) of some drugs can have very different physiological effects.
Controlling this molecular arrangement is challenging and often possible
only for very specific types of reaction.
That's why the process devised by Thorsten Bach and colleagues will be
welcomed. In a Letter published in this week's Nature, the team propose a
way to control enantiomer selectivity in a reaction induced by light. Such
'photochemical' processes are quite common in synthetic chemistry, as well
as being essential to the natural process of photosynthesis. Often they
involve moving an electron from one molecule, or part of a molecule, to
another, and it is such a photoinduced electron transfer process that Bach
and colleagues have now brought under control.
The researchers do this with a catalyst: an organic molecule that guides the
reaction along the right path and then moves off to do the same so another
molecule. The catalyst in this case is a molecule that sticks to the
reactant molecule (which is to be transformed into a product molecule with a
particular handedness), absorbs light and then uses the energy to take an
electron from the reactant. As a result of this electron transfer, the
reactant becomes rearranged into a product molecule with the desired
handedness - here, the catalyst acts as a kind of glove that only the
correct hand will fit. A News and Views article by Yoshihisa Inoue
accompanies this research.
CONTACT
Thorsten Bach (Technische Universität München, Garching, Germany)
Tel: +49 89 28913330; E-mail: [email protected]
Yoshihisa Inoue (Osaka University, Suita, Japan)
Tel: +81 6 6879 7920; E-mail: [email protected]
[8] And finally... Solvent switching (p1102)
The chemical industry wastes money and resources in each successive step of
a chemical reaction in which the solvents have to be removed and replaced.
However, these economic and environmental costs could be avoided in the
future by using just one solvent whose properties can be adjusted to suit
multiple steps in the reaction process. A Brief Communication in this week's
Nature describes one such 'smart' solvent: it can be switched simply and
reversibly between one set of characteristics and another.
The switchable solvent is an equal mixture of an alcohol and amine base. By
exposing the solvent to carbon dioxide gas at room temperature and
atmospheric pressure, Philip Jessop and colleagues found that it switched
from a nonpolar, oil-like solvent to a polar, water-like solvent. The
process takes an hour, and results in a liquid salt that can be reversed
back to its original form by bubbling nitrogen or argon gas through the
liquid at room temperature.
If further switchable solvents are found, they could reduce the
environmental impact of producing chemicals such as pharmaceuticals.
CONTACT
Philip Jessop (Queen's University, Kingston, Canada)
Tel: +1 613 533 3212; E-mail: [email protected]
ALSO IN THIS ISSUE...
[9] Reversing histone methylation (pp1103-1106)
[10] Early planetesimal melting from an age of 4.5662 Gyr for
differentiated meteorites (pp1127-1131)
[11] Ferroelectricity from iron valence ordering in the charge-frustrated
system LuFe2O4 (pp1136-1138)
[12] Base stacking controls excited-state dynamics in A·T DNA
(pp1141-1144)
[13] Seasonal oscillations in water exchange between aquifers and the
coastal ocean (pp1145-1148)
[14] Frozen magma lenses below the oceanic crust (pp1149-1152)
[15] Translational control of hippocampal synaptic plasticity and memory
by the eIF2a kinase GCN2 (pp1166-1170)
[16] Aminoglycoside antibiotics induce bacterial biofilm formation
(pp1171-1175)
[17] Hassall's corpuscles instruct dendritic cells to induce CD41CD251
regulatory T cells in human thymus (pp1181-1185)
[18] Cryptic chlorination by a non-haem iron enzyme during cyclopropyl
amino acid biosynthesis (pp1191-1194)
[19] Atomic model of a myosin filament in the relaxed state (pp1195-1199)
[20] Virus develops independently of host (pp1101-1102)
ADVANCE ONLINE PUBLICATION
***This paper will be published electronically on Nature's website on 24
August at 1800 London time / 1300 US Eastern time (which is also when the
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[21] The yeast Pif1p helicase removes telomerase from telomeric DNA
DOI: 10.1038/nature04091
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GERMANY
Garching near Munich: 7
Munster: 7
Regensburg: 20
JAPAN
Hyogo: 11
Ibaraki: 11
Sendai: 11
Tsukuba: 11
Yokohama: 15
NEW ZEALAND
Wellington: 10
THE NETHERLANDS
Den Burg: 2
Nijmegen: 2
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Exeter: 6
London: 6
Oxford: 3, 6
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Cambridge: 13, 18
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