T
his recreation of the
Mona Lisa may be a little
blurry, but it’s still the best
effort at reproducing a
masterpiece using genetically
modified bacteria that we’ve
ever seen. The picture was
made by Italian scientists at
the Sapienza University of
Rome. Rather than trying to
pull off some kind of germ-
based art fraud, the
researchers were investigating
methods for making large
populations of bacteria move
around on command. To do
this, the team modified the
DNA of E. coli bacteria so they
would produce the protein
proteorhodopsin in their tiny
flagella – the ‘tails’ which the
bacteria use to move around.
Proteorhodopsin is light-
sensitive, and is used in some
microorganisms to generate
energy.
“Much like pedestrians who
slow down when they
encounter a crowd, or cars
that are stuck in traffic,
swimming bacteria will spend
more time in slower regionsthan in faster ones,” said lead
author Dr Giacomo
Frangipane. “We wanted to
exploit this phenomenon to
see if we could shape the
concentration of bacteria
using light.”
The proteorhodopsin in the
bacteria’s flagella meant they
could be made to move either
faster or slower, depending on
how much light they were
exposed to. Slower-moving
bacteria would clump together
(to form dark areas in the
picture), while faster-moving
bacteria spread further apart
(to create lighter areas in the
picture).
The researchers hope that by
learning how to control
bacterial movement, we may
eventually be able to create
microscopic ‘machines’ to
deliver drugs within the body.
The technique could also have
applications in 3D-printing.Your smile would be
enigmatic too, if your
face were made up of
a million swimming
bacteria.M
enopause is rare in the
animal kingdom. While
many species may be less
likely to reproduce as they
near the end of their life,
until now only three animals
were known to have an
‘evolved strategy’ where
females have a significant
post-reproductive lifespan:
humans, killer whales and
short-finned pilot whales. But
now researchers at the
University of Exeter and the
University of York have added
two more toothed whale
species to that list: belugas
and narwhals.
The team studied dead
whales from 16 species and
found dormant ovaries in
older beluga and narwhal
females, indicating that
they’d gone through
menopause. The finding
suggests that these species
are likely to have social
structures that involve female
beluga whales and narwhals
living among a greater
number of close relatives as
they age.
“For menopause to make
sense in evolutionary terms,
a species needs both a
reason to stop reproducing
and a reason to live onafterwards,” said Dr Sam
Ellis of the University of
Exeter. “In killer whales, the
reason to stop [reproducing]
comes because both male
and female offspring stay
with their mothers for life, so
as a female ages, her group
contains more of her children
and grandchildren. This
increasing relatedness means
that, if she keeps having
young, they’re competing
with her own direct
descendants for resources
such as food. The reason to
continue living is that older
females can be of great
benefit to their offspring and
grand-offspring. For example,
their knowledge of where to
find food helps the group as
a whole survive.”
Studies of ancestral human
remains suggest they had
similar social structures,
which may explain why
menopause has evolved in
our own species, the
researchers say. “Looking at
other species like these
toothed whales can help us
establish how this unusual
reproductive strategy has
evolved,” said Prof Darren
Croft, also of the University
of Exeter.When you live in frigid
Arctic waters, hot
flushes don’t seem
that bad...Quickies
A The subject of Leonardo
Da Vinci’s Mona Lisa was an
Italian woman whose full
name was Lisa Gherardini.
A The painting has its own
mailbox at the Louvre
because it receives so many
love letters from adoring
fans.Shorts
7 INNOVATIONScientists paint
a mini Mona Lisa
using bacteria
7 NATUREBeluga whales and narwhals
go through menopause