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10 | NewScientist | 8 June 2013


Hungry Pac-Man

alga hints at

origin of plants

A TINY alga with a mouth could help
explain how plants became green.
Plants get their pigment from
cellular components called plastids,
which are also essential for
photosynthesis. Plastids are thought
to have started out as free-living,
photosynthesising bacteria that were
engulfed by the earliest algae over a
billion years ago. They have continued

to live inside algae and their more
complex plant descendants ever since.
However, nobody knows how this
symbiotic relationship blossomed,
because we know of no plant or alga
that can swallow bacteria like this.
Now Shinichiro Maruyama of the
National Institute for Basic Biology in
Okazaki, Japan, and colleagues think
they have found one. The pair studied
Cymbomonas, a single-celled alga
which belongs to one of the oldest
algal groups. Cymbomonas ordinarily
survives by photosynthesising, but
when they grew it under low light
levels it took to eating bacteria

(Current Biology, doi.org/mm2).
However, rather than extending
a blobby “arm” to engulf its prey like
other single-celled organisms,
Cymbomonas sucked the bacteria
up into a feeding tube. The tube
led to a bubble-like chamber called
a vacuole, a sort of microscopic
stomach where the bacteria were
digested. Maruyama says that the
first green algae may have taken up

their bacterial companions in the
same way as Cymbomonas, except
they didn’t digest them.
The engulfed bacteria could
have survived in their new hosts by
breaking through the walls of the
feeding duct or escaping from the
vacuole, says Maruyama.
Laura Katz of Smith College in
Northampton, Massachusetts,
says Cymbomonas could have
kept this ancient mode of feeding
as a backup, while other algae
abandoned it. “Most algae got
lazy and took to lying in the sun,”
she says. Michael Marshall n

“Cymbomonas kept the
ability to eat bacteria
while other algae took
to lying in the sun”


New unified theory

needs a check-up

PHYSICISTS have a problem, and
they will be first to admit it. The two
mathematical frameworks that govern
modern physics, quantum mechanics
and general relativity, just don’t play
nicely together. Eric Weinstein, a
consultant at a New York City hedge
fund, says the way to unify them is
to find beauty before seeking truth.
Weinstein hit the headlines last
month after mathematician Marcus
du Sautoy at the University of Oxford
invited him to give a lecture detailing his
new theory of the universe, dubbed
Geometric Unity. Du Sautoy also
provided an overview of Weinstein’s
theory on the The Guardian newspaper
website on 23 May (bit.ly/11RKPff).
Few physicists attended Weinstein’s
initial lecture, and with no published
equations to review, the public airing
of his theory has generated heated
controversy. When Weinstein repeated
his lecture at Oxford last week, a
number of physicists were in the
hall. Most remain doubtful.
Physicists working on unification
are usually trying to create a quantum
version of general relativity. Weinstein
believes we should instead start with

the basic geometric tools of general
relativity and extend the equations in
mathematically beautiful ways. Then
you can try to match the equations
with reality.
At the heart of Weinstein’s theory
is the “observerse”, a 14-dimensional
space that contains our familiar
four-dimensional world, with its three
of space and one of time. The extra

One theory to unify them all,
and in the darkness bind them

Jacob Aron

dimensions arise by extending the
mathematics of the original four.
The mathematical symmetries of
the resulting equations predict three
families of particles, as described by
the standard model of physics, though
the third family would behave a bit
differently. His theory also predicts
new, as-yet-undiscovered particles
along with their mirror particles,
which could account for dark matter.
But we should already have seen
some of Weinstein’s new particles,
if they exist, says Oxford physicist

Joseph Conlon. Some should be linked
to the strong force, one of the four
fundamental forces in the standard
model. The Large Hadron Collider at
CERN near Geneva, Switzerland, has
been smashing particles together at
high enough energies to overcome the
strong force, creating showers of more
elusive particles, including the Higgs
boson. Weinstein’s particles should
have been in such showers.
Also, any update to the central
equations of physics should give results
that are only slight corrections, says
John March-Russell, also at Oxford.
Right now, equations and experiments
agree to 1 part in 10 billion, so the new
theory would have to be a very small
tweak. The size is yet to be revealed.
What’s more, it should be possible to
perform a calculation called anomaly
cancellation on Weinstein’s equations,
says Conlon. This checks whether a list
of particles is a consistent extension of
the standard model. If his particles fail
the test, the theory is wrong.
Weinstein admitted that he did not
yet have answers to these and other
questions raised by his talk, and he
has remained vague about when and
where his equations will appear in
print. In some sense, though, it is a
happy resolution to the media storm:
Weinstein has found physicists who
are willing to listen to and guide him,
and his theory will face needed scrutiny.
Geometric Unity could still turn out
to be a theory of everything – or just a
nice bit of mathematics. n






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