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Meet the Gribbles!
Making Links across Triple Science
C Worden, Blackfen School for Girls
Meet the Gribble!
Find the full article and video clip about the gribble at this link on the
BBSRC website. The same article without pictures and video has been copied
below.
http://www.bbsrc.ac.uk/news/industrial-biotechnology/2012/121128-fmeet-the-gribbles.aspx
1. Read through the article ‘Meet the Gribble’. Highlight 50 words that
you think are important to the topic.
2. Select the 20 most important words
3. Explain how the gribble is being used using all 20 words in your
explanation
Tiny bugs could supply the enzymes needed for modern bioenergy.
28 November 2012
It's said that great things happen from small beginnings. In this case, a tiny marine
crustacean could revolutionise biofuel production and usher in a new generation of liquid
propellants for buses, cars and aeroplanes that would effectively be powered by wood.
A huge amount of energy is stored in woody biomass. But getting at it is harder than it sounds
because of the effort needed to prise the sugars in wood out of the tough structures in which it is
encased. Enter the gribble: this 2mm creature, like a very small wood louse that lives in the sea,
can digest wood all by itself.
BBSRC-funded researchers are looking to harness the power of the gribble's enzymes to release the
sugars from wood that can then be fermented to make biofuels. The major advantage is that waste
materials can be used to make fuels instead food crops, delivering a double bonus in not competing
with land for food production as well as utilising unused materials from timber and agricultural
industries.
The work is part of the BBSRC Sustainable Bioenergy Centre (BSBEC), a £24M investment that
brings together six world-class research programmes to develop the UK's bioenergy research
capacity.
Wood 'worm'
The gribble is a marine isopod of the family Limnoriidae. They were the scourge of the naval world
for centuries because of their abilities to eat entire ships or render them sluggish and useless for
long voyages. In fact, their wood-boring abilities are legendary and still present a threat to piers
and harbours today (ref 1).
The woody parts of plants are made of lignocellulose from cell walls. Energy-rich polysaccharide
(sugar) polymers comprise up to 70% of plant cell walls, making them one of the most abundant
reserves of biomass on the planet and ripe for industrial processes such as fermentation (ref 2). The
snag is getting at those sugars requires energy to prise the polysaccharides from the tough lignin
coating, which is currently achieved by heating at very high pressure.
The way the gribble attacks wood is much more efficient and almost unique. Other wood-digesting
creatures such as termites possess gut microbes that do the digesting for them. Not so the gribble,
which has a sterile gut – it must be processing the wood itself. This clue has led Professor Simon
McQueen-Mason of the University of York and colleagues to take a very close look at the enzymes in
the gribble gut.
"We've been working on this animal for two-to-three years," says Professor Simon McQueen-Mason.
"At the beginning we did a profile of the genes in the digestive system to see the major enzymes
are that are involved in digestion."
The species they are most interested is Limnoria quadripunctata, a convenient animal to culture in
the lab, but a major pest species (ref 3) in temperate waters around the world where it is probably
still dispersed by wooden ships. What they have found is that the gribble is exposing the wood it
swallows to a kind of pre-treatment to loosen up the structure of the wood before the main
enzymes get to work.
Using electron microscopy as well as micro-computed tomography (ref 4), a miniature version of
the 3D x-ray CT scans undertaken in hospitals, scientists have located a gland alongside the gribble
gut called the hepatopancreas; not only does it absorb and stores toxins out of harm's way, it also
secretes a chemical that breaks down the lignocellulose and allows other enzymes to break down
the sugar components. A model of biological efficiency, McQueen-Mason thinks this chemical pretreatment also helps to keep the gribble gut free of microbes.
While fishing around the gribble gut, researchers have also found cellulose-degrading enzymes from
the glycosyl hydrolase family which had never been seen in animals before, only in higher wooddigesting fungi, and in protists that live symbiotically in the gut of termites. "Virtually all other
examples of this enzyme family are non-marine and the only others produced by animals are from
other crustaceans that are not capable of breaking down wood," says Dr Simon Cragg from the
Institute of Marine Sciences Laboratories at the University of Portsmouth. "Wood probably
represents the most challenging, though energetically rewarding of substrates."
Creatures great and small
The challenge now is to recreate the processes taking place in the gribble at an industrial scale.
McQueen Mason thinks that technology from the gribble – in the way that it pre-treats wood before
digestion proper – will allow industrial scale pre-treatment of woody biomass to happen at much
lower temperatures. "We also hope that some of the enzymes we find in the gribble, which we know
function better than the ones we have under particular conditions will also be applicable in this
process," he says.
Another way of increasing efficiency is to decode the structure of the gribble enzymes. This is
necessary so they can be cheaply produced in bacteria; it may also be possible to tinker with them
to make them even more efficient at certain temperatures for example, or when breaking up harder
substrates.
To delve into the enzyme in unprecedented detail, Cragg's colleague John McGeehan, also of the
University of Portsmouth, has been using a particle accelerator, the Diamond Light Source
synchrotron, based in Harwell, Oxfordshire; it's powerful x-ray beam lines can be used to elucidate
complex molecular structures and their results are due to be published soon.
Sequencing the DNA of the gribble is also underway. "We now have the opportunity to build a whole
genome for our creature, supported by our York-based colleagues, by The Genome Analysis Centre
(TGAC) in Norwich, and US collaborators at three different institutions," says Cragg. Funded by a
BBSRC Partnering Award, the partnering project started in May 2010 and the US partners will tackle
DNA sequencing of the whole gribble genome; TGAC will then assist the University of Portsmouth
team in assembling it. A workshop with all collaborating members will then tackle annotation of the
genome [identifying important functional elements] around September 2013.
In the future, given the demands and complexities of providing sustainable biofuels, this type of
fundamental work is unlikely to be restricted to just the tiny gribble. Enzymatic and genetic analysis
can also be applied to the limited range of critters that can digest wood without microbes, which
include some mussel-like molluscs.
"We have identified some other animals with remarkable abilities to deconstruct tough substrates
which we know have unusual digestive systems and may have enzymes of biotechnological
potential, " says Cragg. "Our insights will also drive innovation in benign wood protection methods
for the marine environment."
My top 20 key words
My overall summary of the article using my top 20 key words
What aspects of the Triple Science Course can you identify within the
article?
Biology of the Gribble
Find an image of a gribble. Draw/stick it here. Label the diagram.
If scientists are to study the gribble in order to gather the enzyme, how
must they keep live gribbles in the lab? How is the gribble adapted to its
environment?
Relevant to B1 – what can students find out about adaptations of marine
crustaceans, marine environments
Find a food chain including the Gribble. Use this to create a pyramid of
biomass.
Producer at bottom – likely to be wood/plant material
Some sort of fish probably eats gribble – depending on student research.
The Carbon Cycle
Draw and label the carbon cycle here showing where the Gribble fits in.
Standard carbon cycle diagram. Gribble eats woody plant material and
respires releasing carbon dioxide etc. Gribble dies, becomes limestone under
right conditions
Explain the diagram here.
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Enzymes
The gribble contains an enzyme which digests wood.
Explain what an enzyme is
an enzyme is a biological catalyst which means it speeds up the reactions in
living things, such as reactions involved in respiration, photosynthesis,
growth, protein synthesis.
Describe the structure of enzymes in as much detail as you can, refer to
genes in your explanation.
Enzymes are proteins. Proteins made up of carbon, hydrogen, oxygen and
nitrogen. Proteins, large molecules made of a long chain of smaller molecules
called amino acids. Sequence of amino acids specific to every protein. The
molecule is bent and folded into a special shape, often has a dpression or
pocket on its surface called the ‘binding site’.
Name the enzyme family that the gribble uses to digest wood and state what
the wood would be broken down into.
glycosyl hydrolase family, the wood would be broken down into sugars
What factors would scientists have to change/investigate when finding out
the optimum conditions for this enzyme to do its job?
Temperature, pH
Explain how could immobilized enzymes be useful in this context and what
would be the advantages of this method over using the enzyme in living
organisms?
If the enzyme could be immobilized and still used, then this would be useful
as the enzyme could be used over and over again, the enzyme would not have
to be separated from the sugars/bacteria to be used again. This would be
more cost effective. Immobilising enzymes can be advantageous over using
living things because there are risks when workingwith bacteria, they can
mutate and create dangerous forms, they require special conditions to
survive such as temperature, which could be expensive. These sorts of
conditions also require energy use to maintain which contributes to global
warming.
Genetic Engineering
Draw a diagram and explain how genetic engineering could be used to
transfer genes from the gribble to bacteria, so that the enzyme could be
captured.
Standard diagram of genetic engineering diagram
Explain the diagram here
answer should use key words; enzymes, plasmid, gene, bacterial, DNA,
asexually, extracted, purified, chromosome
Cells
Draw and label a diagram of a plant cell showing where the tough cell wall
containing cellulose can be found
Draw and label a diagram of a bacterial cell.
Biofuels
Use the article to explain the advantages of using the gribble enzyme to
release energy for biofuel from waste wood.
Using waste wood prevents this material from ending up in landfill and
releasing methane into atmosphere as it decays, using waste wood reduces
use of land to grow biofuels, this reduces competition for land for growing
food crops
How is ethanol produced from biomass? You could use a diagram or flowchart
in your answer.
_Biomass is broken down using bacteria into sugars. The sugars are then
fermented using anaerobic respiration by yeast. Yeast breaks the sugar
down into ethanol and carbon dioxide. The ethanol can then be used as a
biofuel.
Why are wood and straw not used much commercially to produce ethanol?
Wood and straw are not used much to produce ethanol as the sugars that
are needed for anaerobic respiration are stored in cellulose and the cellulose
cannot be easily converted into sugars
Biofuels are carbon neutral. Explain what this term means.
Carbon neutral fuels are fuels that have no net effect on carbon dioxide
levels in the atmosphere. This is because the carbon dioxide they are
releasing when burnt is only the carbon dioxide they took in whilst they were
alive.