14 | New Scientist | 17 August 2019
GOLIATH frogs are the biggest frogs
in the world, and they may have
evolved to such a size by moving
2-kilogram rocks to build nests.
This endangered species,
Conraua goliath, can reach
34 centimetres long and weigh over
3.2 kilograms. It is only found in
Cameroon and Equatorial Guinea.
Mark-Oliver Rödel at the Berlin
Museum for Natural History in
Germany and his team worked with
local people to find frogs’ nests in
the Mpoula river in Cameroon.
The nests are small pools within
streams. Some are natural but
others are built by the frogs clearing
rocks away. The team didn’t catch
the frogs in the act, but locals said
they had seen them move heavy
rocks. They did see stones that had
been turned upside down (Journal
of Natural History, doi.org/c9bq).
Rödel suspects the frogs use their
hind legs to move the rocks, as they
are stronger than their front legs. ❚Animal behaviourFOR decades we have known that
bacteria can evolve resistance to
antibiotics. Now it looks like other
drugs, including ibuprofen, may
help this resistance spread.
Different species of bacteria
are able to swap genetic material,
a process that has enabled many
strains to acquire antibiotic
resistance genes. Now Yue Wang
at the University of Queensland
in Australia and colleagues have
found that five commonly used
non-antibiotic drugs appear to
encourage this gene swapping.
The study looked at six drugs:
the anti-inflammatories
ibuprofen, naproxen and
diclofenac, as well as the lipid-
lowering drug gemfibrozil, thebeta-blocker propranolol and
iopromide, which is used to
produce better X-ray images.
Each of the drugs was mixed
in a vial containing two strains
of bacteria, one of which was
resistant to three types of
antibiotic, while the other was
resistant to a different, fourth
type of antibiotic.
After eight hours of incubation,
the mixtures were tested to see
if they contained any bacteria
that could now resist all four of
the antibiotics.
No bacteria placed in control
mixtures, which didn’t contain
any of the drugs, became
capable of resisting all four
antibiotics. Neither did thebacteria exposed to iopromide.
But quadruple-resistant
bacteria did arise after exposure to
ibuprofen, naproxen, diclofenac,
gemfibrozil or propranolol. This
occurred even when ibuprofen,
naproxen and gemfibrozil were at
extremely low concentrations – as
little as 0.005 milligrams per litre.
DNA analysis confirmed that
resistance genes had swappedbetween the two strains of bacteria.
The team found that exposure
to these five drugs was linked to
cellular changes that may have
made it easier for the bacteria to
release and absorb each other’s
DNA (bioRxiv, doi.org/c9bs).
The study shows that we have
much more to learn about what
drives the transfer of resistance
genes, says Adam Roberts at the
Liverpool School of Tropical
Medicine, UK.
Katherine Duncan at the
University of Strathclyde, UK,
notes that, outside of laboratory
conditions, many other chemicals
may accelerate or decelerate the
gene transfer process. ❚Antibiotic resistanceCommon drugs may help resistance spread
Michael MarshallIbuprofen may
encourage
bacteria to
swap genes
that give
resistance to
antibioticsGiant power-lifting frogs
The world’s largest frog builds its own ponds using heavy stones
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