Hot and bothered corals can cope

868 23 MAY 2014 • VOL 344 ISSUE 6186 sciencemag.org SCIENCE

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SUBSURFACE MICROBES

Mapping sub–sea-floor communitiesThe sea floor is teeming with

microbes, whose sheer numbers

produce a major effect on the

global biogeochemical cycles

of carbon, sulfur, and other

important nutrients. Bowles et al.

constructed a map showing how

deeply sulfates penetrate marine

sediments worldwide and how

Edited by Stella HurtleyI N SC IENCE J O U R NA L S

RESEARCHA potential therapeutic target for adrenal Cushing’s syndrome p. 917

quickly that sulfate is chemi-

cally reduced by microbes in the

sub–sea-floor. Globally, almost a

third of the organic carbon that

reaches the sea floor is con-

sumed during sulfate reduction,

and the vast majority of micro-

bial cells in the sub–sea-floor

at continental margins get their

energy through the biochemical

processes of fermentation and

methanogenesis. — NW

Science, this issue p. 889.

DEEP EARTH

Delving deeper into the lower mantle Earth’s lower mantle is an

enigmatic region, a transition

zone between slowly churning

solids and a liquid outer core.

Large seismic structures and

discontinuities in this region are

probably due to sharp gradients

in temperature, composition,

or mineralogy. Teasing apart

the precise effects of these

factors requires experiments at

lower mantle temperatures and

pressures (see the Perspective

by Williams). Zhang et al. found

that the major mineral phase of

the lower mantle decomposes

into two minerals. Andrault et

al. show how the melting of sub-

ducted basalt from the oceanic

crust will form pile-like struc-

tures on top of the core/mantle

boundary. — NW

Science, this issue p. 877, p. 892; see also p. 800.

COSMOLOGY

Confirming cosmic dual conjecture Quantum mechanics and gravity

can seem to contradict each

other. Superstring theory may

provide a route to reconcile the

two, thanks to the gauge/gravity

duality conjecture, which allows

the system to be described

mathematically. However, this

conjecture has yet to be formally

confirmed. Hanada et al. (see

the Perspective by Maldacena)

performed a simulation of the

dual gauge theory in the param-

eter regime that corresponds

to a quantum black hole. Their

results agree with a prediction

for an evaporating black hole,

including quantum gravity

corrections, confirming that

the dual gauge theory indeed

provides a complete description

of the quantum nature of the

evaporating black hole. — ISO

Science, this issue p. 882; see also p. 806.

CORALS AND CLIMATE

Hot and bothered corals can copeHow well can corals adapt to

temperature extremes? Better

than anticipated, it turns out.

Corals from reef pools with

wide temperature fluctua-

tions resist stress better than

corals from less extreme

pools. Nevertheless, corals

transplanted into the hotter

and more variable conditions

soon acquired thermal toler-

ance. Palumbi et al. (see the

Perspective by Eakin) found

that the tougher specimens pro-

duced more of certain proteins,

such as the tumor necrosis fac-

tor receptor superfamily, which

protected them from the effects

of heat. Ramping up heat shock

and transport proteins yielded

heat tolerance far more rapidly

than mutation and adaptation.

Hopefully, this ability will allow

some mitigation of climate

change on coral reefs. — CA

Science, this issue p. 895; see also p. 798.

GUT MICROBIOTA

Bacteria breach intestinal barriersIn an ironic complication of liver

cirrhosis, beneficial microbes

can escape from the gut and

cause serious infections—or

EVOLUTION

Ruffling ancient ratite feathers

Biologists have often pointed to the breakup of the super-

continent Gondwana to explain how related species

ended up on far-flung continents, but as new research

shows, that explanation doesn’t fly with ratite birds.

Ratite birds are a lineage of large, mostly flightless birds

including the African ostrich, the Australian emu, the South

American rhea, the diminutive New Zealand kiwi, and the

extinct Madagascar elephant bird. Mitchell et al. examined the

phylogeny of these birds, adding ancient mitochondrial DNA

sequences from the extinct elephant bird. It seems that ratites

originated from flighted ancestors who evolved large sizes and

loss of flight only after flying to their new homes. — LMZ


An adult kiwi and an elephant bird egg.

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23 MAY 2014 • VOL 344 ISSUE 6186 869

even death. Balmer et al. now

show that the blood vessels of

the healthy liver form a bar-

rier to runaway gut bacteria.

However, in animal models of

liver disease and gut dysfunction

and in patients with nonalcoholic

liver disease, the liver is unable

to capture these escapees. The

bacteria then leak into the blood

system, activating immune

responses that break down the

mutualistic relationship between

the gut microbes and the host.

This type of breakdown is an

important complication of liver

disease. — OMS

Sci. Transl. Med. 6, 237ra66 (2014).

BONE PHYSIOLOGY

Another way of growing strong bonesTo stay strong, bones are con-

stantly rebuilding themselves.

Thyroid hormones regulate this

process by entering cells and

binding to nuclear receptors,

which travel to the nucleus,

where they change gene expres-

sion. However, these hormones

also stimulate rapid cellular

changes that do not require gene

regulation. Kalyanaraman et al.

found a different form of nuclear

receptor in bone cells. When

bound to thyroid hormones, this

Edited by Kristen Mueller

and Jesse Smith IN OTHER JOURNALS

NEUROSCIENCE

How the brain responds to fairnessMany people consider freedom

of choice and fairness funda-

mental values, but what are

their neural bases? To probe

the question, Aoki et al. had

pairs of people put their heads

in functional magnetic reso-

nance scanners and then play a

game. When both players were

offered an equal number of

choices, they were more likely to

report feeling happy, and their

brain scans showed increased

activity in the area called the

ventromedial prefrontal cortex.

In contrast, when the combined

absolute number of options

available to players increased,

so did activity in the ventral

striatum. Because these regions

have been implicated already in

value processing, these results

may illuminate how a sense of

fairness evolved in the human

brain. — PRS

J. Neurosci. 34, 6413 (2014).

receptor increased the numbers

of bone cells and protected

them from death. When the

researchers treated mice lacking

thyroid hormones with a com-

pound that mimicked the effects

of this receptor, their bone cells

grew normally. — JFF

Sci. Signal. 7, ra48 (2014).

CANCER IMMUNOLOGY

Origins of tumor macrophages To help the immune system

fight cancer, it is important to

understand the origins and

functions of immune cells in

tumors and the surrounding

tissues. One type of immune

cells, macrophages, is present

both in tumors and in nearby

noncancerous tissue, but the

relationship between these

two cell populations is unclear.

Franklin et al. found that tumor-

associated macrophages in

mouse mammaries differed in

form, function, and origin from

macrophages found in nearby

noncancerous mammary tissue.

Moreover, when they removed

macrophages from the tumors

but not the other mammary

tissue, tumors shrank and

cytotoxic T cells—another kind

of immune cell that kills tumor

cells—infiltrated the tumors.

Tumor-associated macrophages

may thus be an important thera-

peutic target. — KLM


NEUROSCIENCE

Decisions, decisions, decisions… Flies, like humans, deliberate

before making perceptual judg-

ments: They ponder difficult

decisions longer than they

do easy ones. DasGupta et al.

measured reaction times in

flies choosing between different

smells. Mutations in a particular

gene, they found, could cause

indecision. Mutations in the

same gene are implicated in

intellectual disability, learning

deficits, and language impair-

ment. — PRS


Thyroid hormones increase the number

of cells (blue) in trabecular bone.

CELL MOTILITY

Cells need to stay in shape, too

To move efficiently, people need to stay in shape—and

the same is true for cells. Burnette et al. looked at the

3D organization of contractile fibers used by living

animal cells as they crawled about on a surface. The

cells adopted a wedge-like shape with a wide, flattened

front end dragging a slim rear. To keep moving, the cells used

a counterbalanced contraction-adhesion system. At the top

of the cell, a network of contractile fibers made from actin

and myosin (the same proteins used in muscles) coupled to

noncontracting stress fibers anchored to the cell’s surface.

Understanding how cells move is important for understand-

ing normal development, wound healing, and metastasizing

tumor cells. — SMH

J. Cell Biol. 205, 83 (2014).

Actin visualized in a crawling cell.

Published by AAAS

sciencemag.org SCIENCE870-B 23 MAY 2014 • VOL 344 ISSUE 6186

SURFACE SCIENCE

Probing bonding profiles with a CO tipGreater resolution has been

achieved in atomic force

microscopy by terminating the

tip with a sharper probe: an

adsorbed CO molecule. Chiang et

al. now show that the adsorbed

CO tip can reveal the bonding

within cobalt phthalocyanine

molecules absorbed on silver or

gold surfaces. Inelastic tunneling

spectroscopy reveals variations in

the vibration excitation of the CO

molecule that can map out the

internal bonding of the molecules,

as well as hydrogen bonding

between molecules. — PDS

Science, this issue p. 885

INFECTIOUS DISEASE

Progress toward an effective malaria vaccineThe history of efforts to develop

a malaria vaccine has been long

and difficult. Raj et al. probed

for molecules produced by

this blood parasite that are

recognized by natural immune

responses of people living

in malaria-endemic areas of

Africa. One, PfSEA-1, blocked

parasite exit from red blood

cells. Vaccination experiments

with mouse malaria showed

almost fourfold reduction in

parasitemia; moreover, passive

transfer of PfSEA-1 antibodies

transferred protection from

mouse to mouse. Encouragingly,

the presence of PfSEA-1 antibod-

ies correlates with significant

protection from severe malaria

in children and adolescents from

Kenya and Tanzania. — CA


MICROBIAL GENOMICS

In translation, sometimes stop can mean goThe genetic code appears to

be largely conserved across all

domains of life. Although limited

deviations have been reported,

Ivanova et al. used metagenom-

ics to survey the prevalence of

stop codon reassignment in

naturally occurring microbial

populations. Certain bacteria

and bacteriophages exhibited

lineage-specific recoding of their

stop codons. In one specific

phage, the genome was restruc-

tured into two genetic sets.

One set of genes was encoded

in a way that didn’t gel with

the host genome and probably

helped with infection. A second

set of more host-compatible

sequences encoded proteins

expressed in the later stages of

infection. — LMZ


NEUROSCIENCE

Firing, wiring, and Hebbian remodelingCorrelated neuronal activity is

generally thought to drive circuit

remodeling in the central ner-

vous system. This model, first

proposed by Hebb, is strongly

supported by several lines of

evidence, though it has been

difficult to directly observe such

changes in real time. Munz et

al. developed an experimental

approach to watch structural

remodeling of neuronal axons

in vivo at high temporal resolu-

tion. They measured changes in

synaptic efficacy while present-

ing specific patterned stimuli to

test the Hebb model. Although

the key predictions of Hebbian

developmental plasticity were

upheld, the mechanistic details

of how this occurred were unex-

pected. — PRS


CANCER GENOMICS

Candidate Cushing’s culprit identifiedCushing’s syndrome is a rare

condition resulting from the

excess production of corti-

sol. About 15% of Cushing’s

syndrome cases are associated

with an adrenocortical tumor.

However, the genetic etiology of

these adrenocortical tumors is ill

defined (see the Perspective by

Kirschner). Cao et al. and Sato et

al. both performed whole-exome

sequencing of tumors from indi-

viduals with adrenal Cushing’s

syndrome and compared it with

the patient’s own matched non-

tumor DNA and identified

recurrent mutations in the

protein kinase A catalytic subunit

alpha (PRKACA) gene, as well as

less frequent mutations in other

putative pathological genes.

The most common recurrent

mutation activated the kinase,

which may suggest a potential

therapeutic target. — LMZ

Science, this issue p. 913, p. 917;

see also p. 804

RESEARCH

Edited by Stella HurtleyI N SC IENCE J O U R NA L S

Published by AAAS

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Hot and bothered corals can cope