Posts Tagged ‘Fungus’

The brewer’s yoke, the domestication of microbes

// July 15th, 2012 // Comments Off on The brewer’s yoke, the domestication of microbes // Recent Research

Something happened when I was spliced, something wrong. Some random event in my chromosomes, I suppose it was. In any event, I wound up lacking. My sister took all the toxin genes, and I was left with nothing.

It’s a scary world out there for a fungus without a toxin. How would I strike fear into the hearts of all animals who dared to eat the plants I was eating? How, without my precious aflatoxin to attack the liver, causing acute sickness or eventual cancer?

Quite simply, I’m surprised I lasted as long as I did before they found me.

Indeed, I’m not sure how they did find me. I had a pretty good disguise, growing colonies of blue along the endless islands of white rice grains, just like my toxic cousins always had. Safe from munching animals by my don’t-eat-me mimicry, the promise of sickness is the discoloured rice.

For some reason, these sake brewers saw past it all. I thought I was a goner when they lifted me up from the wild and plonked me into a house of wood.

Then I saw the food.

A. oryzae in heaven. Image by Forrest O.

It’s hard for mould like me to see, lacking in the eye department, but I knew it was there. An endless carpet of steamed rice. With my filamentous fronds I could touch it. Drill down into it and grow cottony soft, sprout fruiting bodies on the surface and spread on and on.

Call me legion, for we are many. Better yet, call me qū meí jūn in Pinwin, kōji-kin in Japanese, nulook-gyun in Korean or the grandiose Aspergillus oryzae in scientific circles. Back then, some 2000 years ago, I didn’t know who I was, or that I would one day be the National Fungus of Japan.

That’s when the changes happened.

I didn’t notice at first, I don’t know that there was ever a master plan. It felt… natural. Human hands, bristling with microbes and pitted with pores, dropped me into heaven. And when I had eaten the heaven for a time, they picked me up and dropped me once more into fresh heaven.

Incomprehensible! These hands must have spent hours polishing the rice to remove all the husks, then steamed it to perfection, cooled it so I didn’t burn my filaments, then spread it out – just for me! It was like being a king! King Kōji-kin!

I'm a national icon, and pretty cute too. Image by Ryoku Kasinn

As they fed me and I ate, we gradually adapted to please one another. Heaven grew ever more heavenly, until the temperature and humidity was just so.

For my part, I started growing much faster, hell, I had brilliant conditions for it and not a doubt in the world that I could grow as fast as I pleased. Fearlessly fast.

Over generations, they selected only the best for their purposes, which at that stage I knew nothing about. They selected the sons and daughters (hell, we’re all of one gender here) that could best turn rice starch to sugar. They also preferred fungi of least colour, but most smell and flavour. Each generation, the best of me would be plucked and propagated.

Turning starch to sugar is a tricky thing. I suppose the point of starch is to tie up the sugar molecules into a big, complex network so the plant can use them later. For me, kōji-kin I secrete the amylase enzymes, biological machine that chops starch into pieces of sweet. From a couple of recently-licked hands, I’ve learned humans make the same enzyme in their saliva. My amylases, however, not only make glucose, but a few other sugars that produce a wonderful flavour.

But why, pray tell? Have you worked it out yet?

Winemakers use yeast to turn the natural sugars in grapes into alcohol. Beer brewers must malt their barley, partially growing the seed to convert starch to sugar, to ferment it with yeast into alcohol.

And I, the humble fungus, plucked from the wild a millennia ago for a deficit in character. My non-toxic self excels, above all other moulds, in turning rice starch into sugars.

From the beds of heaven, me and my alchemical rice is transferred to the fermenting tank. Mixed with yeast, water and more rice, then left to stew in our own juices for a month.

This mash is pressed and filtered, and the sweet, alcoholic liquid that pours forth is bottled as sake.

Not to ring my own bell filaments, but I make soy sauce and miso too. That’s a whole meal – appetizer, main, and a drink.

Domesticated A oryzae (left) and wild A flavus (right). Image by John Gibbons, Vanderbilt University

These days I hardly recognise myself! So much of me has changed by growing with the sake brewers. Though I still share some 95% of my genome with my wild and toxic cousin A. flavus (and you, human reader, share 99% of yours with a chimpanzee), I am given all I could ever want to eat and praised world-over for my skill in sake making. While A. flavus, the wild thing, is targeted daily for a war against fungi with resistant crops and competitive yeasts.

What must the wolf think of the dog? Or the auroch of the cow? Well, to their accusations I say this: We may change our genes and appearance for protection and care, but, in doing so, we also mould the humans who cooperate with us. Through their attentions and skills, they, too, are domesticated.

This story was inspired by this recent research by Vanderbilt University into the domestication of microbes. “Although people don’t often think about it, we haven’t only domesticated animals and plants, but we have also domesticated dozens of different microbes.” – Assistant Professor of Biological Sciences Antonis Rokas in the press release. You can find more information on brewing sake here, and a beautiful description of koji pampering by interns at a sake house in Japan who blogged their experiences.

ResearchBlogging.orgGibbons, J. et. al. (2012). The Evolutionary Imprint of Domestication on Genome Variation and Function of the Filamentous Fungus Aspergillus oryzae Current Biology

Exploring the blurry line between colony and individual

// August 3rd, 2011 // 1 Comment » // The Realm of Bizzare

I found this great post on the Portuguese man-o-war, known as the bluebottle in Australia, over at Deep Sea News the other day. It’s eating a fish!

The post also said:

Remember this species is colonial and made of four different polyps or zooids, working in unison and dividing labor. The bladder is a single polyp called a pneumatophore. The long tentacles are dactylzooids used for fishing. The dactylzooids bring the fish up to another set of zooids, gastrozooids, responsible for digestion. Last, there is set of zooids, gonozooids, in charge of reproduction.

So it looks like a jellyfish, but it ain’t. It’s a colony of four specialists working together, each with their own nervous system but incapable of living by themselves.

Bluebottle on Woolongong Beach, NSW. Image by Fiona Wilkinson

As I was doing a bit of research about bluebottles and how they sting even when dead and dried up, I came across an interesting question. How do they reproduce? If the gonozooids are responsible for getting jiggy with it, don’t they just make more gonozooids? Where do the rest of the polyps come from?

Well, no one really is a hundred percent sure. I guess that’s fair enough, studying a swarm (a navy) of man-o-wars during mating season doesn’t sound too good. But here’s what they think.

A gonozooid from one man-o-war will make sperm which combines with an egg from another man-o-war gonozooid. Hey presto, you’ve got fertilisation and one embryo – which will become the bladder polyp at the top. That embryo divides several times, then reproduces asexually to make more zooids, which bud out of it. The budding polyps will become either tentacle, digestion or reproduction individuals.

That’s where I got confused. Does this mean that each of the zooids actually come from a single polyp? Are they just differentiated forms of the original polyp, specialised for their particular role? How is this different to a human embryo producing heart cells?

One explanation uses phylogenetics – comparing organisms to see how similar and different they are. Each zooid is similar to solitary Cnidaria (the phylum that includes jellyfish, coral and bluebottles), so can be considered an individual in its own right and a bluebottle as a colony.

But if we define an individual as something with similarity to other individuals, then all the cells of a multicellular organism would be individuals. Are individual humans really colonies of individual human cells? Really, the microbes on and in you outnumber your human cells 10 to one, so you’re more like a walking microbial factory anyway.

White poplars, a kind of aspen, form clonal colonies. Image by Jacob Halun

I think we have a very human-centric model for defining individuals, which is not surprising really. But most species on the planet don’t reproduce like we do, the boundaries between individual and colony are much less clear.

Take aspen trees, which can grow by seeds (sexually) or by underground runners which sprout a tree-clone (asexually.) Over time the runners can decay separating the trees. How can we tell if the trees are individuals or clones, and if we can’t, how do we study adaptation and natural selection?

Tasmania has these Huon pines that are the oldest genetically identical stand of trees which has lasted 10,000 years. Each tree lives about 2,000 years, but the original tree renews itself through genetic clones. Tassie also has the oldest genetically identical plants, clones of King’s lomatia estimated to be at least 43,000 years old.

Strawberries do it too, as do fungus. A single specimen of Armillaria solidepes was found in Oregon the size of 1,220 football pitches and estimated at 2,400 years old. It’s one of the largest organisms in the world.

Where does the individual end and a colony begin? Looking at all the bizarre stuff out there, I can’t help but wonder if we’re the weird ones.

ResearchBlogging.org

Clarke, E. (2010). The Problem of Biological Individuality Biological Theory, 5 (4), 312-325 DOI: 10.1162/BIOT_a_00068

Read it at the homepage of Ellen Clarke

The Freakiest Fungus on the Face of the Planet

// August 4th, 2009 // 2 Comments » // The Realm of Bizzare

This is the freakiest fungus I have ever seen, freakier even than the giant man-eating one in “Field Trip,” my favourite episode of the X-Files (Season 4). The story is a bit like an X-File too, so for the purposes of this blog picture me red-headed, scientifically rigorous and secretly in love with Mulder (that last one’s true.)

This class of fungus they call Cordyceps, and once released their spores drift down like gentle dew upon unsuspecting insects. If successful, the spore will ninja past the exoskeleton and into the host tissue where it begins to grow. And grow. And grow.

When it is big enough it infects the brain and kills the insect. Then, and this is the freaky part, it pushes out the fruiting body out of the insect like an evil seed germinating in fertile soil. And man does it look messed up. Check it out.

Cordyceps unilateralis cordyceps_tuberculata

Some species seem to direct the insect to find a place with the right humidity and temperature to encourage the growth of the fungus just before it dies. It’s discussed awesomely at The Loom, who I am forever grateful to for telling me about this horror-movie.

Speaking of horror movies, David Attenborough did a piece on this once, check it out below. It’s just about the scariest documentary I’ve ever seen, my skin is still crawling from it.

Is anyone else getting a flashback from Alien?

It’s not the only thing that feeds on insects and messes with their heads, the Gordian Worm infects grasshoppers and other insects as a larva, growing to immense sizes (relatively speaking) and then apparently making the insect commit suicide by drowning so that it can escape into the water and swim free as an adult. Reminds me of The Happening. Video below, but be warned, it is creepy.

Crazy, no? Have you ever SEEN anything like it? I… no pirate words can describe it.






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