Tag: microbes

Multicellularity Driven by Bacteria

  • Venue: Science Magazine
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F1.smallMONTREAL, CANADA—When taking a dip this summer you will probably swallow tens, possibly hundreds, of microscopic plankton called choanoflagellates. These common organisms have led to an uncommon insight into how multicellular organisms might have evolved. Bacteria can prompt single-celled choanoflagellates to divide into multicellular versions of themselves, University of California (UC), Berkeley, biologist Nicole King reported last week here at the 71st annual meeting of the Society for Developmental Biology. King hopes the work will prompt biologists to look more closely at the role of microorganisms in the evolution of multicellularity.

To the untrained eye, choanoflagellates look like animals. But they are less complex—the closest living relatives of animals but on an older branch of the tree of life. As such, these organisms can provide clues about what early animals looked like and can help reconstruct the events from more than 600 million years ago that led to the incredible diversity of the animal kingdom.

To investigate the transition to colony life, King decided to sequence the genome of a colony-forming choanoflagellate and compare it with the genome of a unicellular individual. But before sequencing, she asked undergraduate Richard Zuzow to purge the sample of everything but the plankton itself. When Zuzow added antibiotics to get rid of any bacteria, the choanoflagellate colonies disappeared. At first, “I didn’t believe him,” King recalls. But with repeated tests, she became convinced that “the bacteria are the important part of the [multicellular] story,” she says

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Lager-brewing yeast identified in Argentina

  • Venue: BBC
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Scientists have identified a yeast that led to the discovery of lager.

The researchers isolated the new species in the frozen forests of Patagonia in South America.

Their discovery suggests that this yeast crossed the Atlantic hundreds of years ago and combined with one traditionally used in Europe to make ale.

The discovery is described in the Proceedings of the National Academy of Sciences.

A lucky find

The workhorse of brewing, the yeast Saccharomyces cerevisiae, is used worldwide to ferment fruit and grains to make wine, cider and ale.

Lager, which is fermented more slowly and at lower temperatures than ale, is presumed to be a later invention, and was likely stumbled upon when Bavarian monks moved their beer barrels into caves for storage.

In those caves, Saccharomyces cerevisiae, which prefers to grow just above room temperature, is presumed to have been outcompeted in the fermenting beer by a species that thrived at cooler climes.

The modern-day lager-brewing yeast, Saccharomyces pastorianus, which is a fully domesticated species, is probably a hybrid of this cool-loving strain and the ale-brewing species, and survives because brewers keep back a little of the lager each time to seed the next batch with the same yeast.

Lager’s cradle

“The hybrid almost definitely formed accidentally and people adopted it because the beer came out differently,” said evolutionary biologist Chris Hittinger from the University of Wisconsin in Madison, US, who was one of the team behind the discovery.

But researchers have long wondered where the original cool-loving yeast species came from.

That is until Dr Hittinger and his colleagues isolated it from a beech tree in the forests of Patagonia this year.

These forests, where daily lows average around -2C, are the perfect cradle for modern-day lager-brewing yeast. The species has been designated Saccharomyces eubayanus.

“I personally prefer lagers to ales, and I am very grateful that these two distant cousins met up in a Bavarian cellar hundreds of years ago,” Dr Hittinger told BBC News.

Knowing the ancestral strain to the modern day lager-brewing yeast will help scientists pinpoint the effects of domestication in the genome of brewing yeasts.

And there is also the possibility that there are other undiscovered species of yeast in those Patagonia forests that could become the next best brew.

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Monkeys Chew the Cud

  • Venue: Science Magazine
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Eating your greens can be grueling, especially if you are a monkey who dines on a high fiber diet. Some primates overcome their digestive dilemma by hosting microbes in their guts that help them breakdown the tougher leaves, much like cows do. Cows and other ruminants also maximize this symbiotic relationship by regurgitating and rechewing their stomach contents to get the most out of each meal. This behavior was considered unique to four-legged herbivores. Now researchers have witnessed proboscis monkeys that live in the mangroves and swamps of Borneo doing the same (see the video). This is the first evidence that primates ruminate, too, reports the team online today in Biology Letters, and gives us all something to chew over.

:: Read original here ::

Cue factors

  • Venue: EMBL
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Our genes were once thought to be responsible for shaping who we are. But now scientists are having a rethink. Thanks to a glut of data from new sequencing projects, researchers are beginning to recognise that the regions of the human genome that encode proteins are unlikely to be behind the millions of differences between people.

So the question remains: what accounts for these differences? Searching for an answer, biologists have pored over the few individual genome sequences that have been completed so far. And these researchers have asked: if the rare stretches of DNA that code for proteins are not responsible for many of the differences found between humans, then what about the remaining 98% of the genome that does not encode proteins – the so-called non-coding DNA?

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Decloaking the germ

  • Venue: EMBL
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The bacterium Listeria infects humans through contaminated food. Once in the gut, this pathogen can be life-threatening if contracted during pregnancy or by newborns and those with weakened immune systems.

But for most people, an encounter with Listeria causes nothing more than vomiting and diarrhoea because our immune system recognises the
long, propeller-like projections on the bacterial surface – called flagella – and
mounts an assault on Listeria until it is wiped out. Listeria, however, has evolved a way to dodge this fate.

To anyone who has ever tried to cross enemy lines, this bacterium has an enviable ruse. After detecting the warmth of the human body, Listeria shuts down the production of flagella – the equivalent of enveloping itself in an invisible cloak. It does this by activating a protein called motility gene repressor, or MogR for short, which binds to DNA close to the flagella gene and suppresses it.

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Arsenic-munching bacteria found

  • Venue: BBC
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Arsenic-munching bacteria

In the warm, bubbling pools of Mono Lake in California, scientists have isolated a bacterium that fuels itself on arsenic.

Combining light and arsenic, these bacteria make their food and multiply using a chemical that is toxic to most other life forms.

The researchers think using arsenic as an energy source was a process used by ancient bacteria.

Their findings are reported in the journal Science.

Ronald Oremland of the US Geological Survey explained that these bacteria are photosynthetic, using sunlight – like plants – to turn carbon dioxide into food.

What is different about them is that instead of using water in this process, they use arsenic.

The US-based researchers isolated the bacterium from the lake, which lies at the foot of the Sierra Nevada.

Colour film

“These lakes are fed by hydrothermal waters that leach out arsenic-containing minerals from the surrounding rocks,” Dr Oremland told BBC News.

The researchers noticed that the bacteria had colonised small, hot pools, forming colourful “biofilms”.

MonoLake(USGS)

Bacteria living in Mono Lake, California can survive the high levels of arsenic

“We suspected that these bacteria were using arsenic to make a living, so we scraped the biofilms off the rock and studied them under laboratory conditions.”

By first withholding light, then arsenic, the team showed that the bacteria required both to grow.

This the first time an organism has been found that can use arsenic to photosynthesise under anaerobic conditions, Dr Oremland believes.

He suspects that this is an ancient ability in bacteria.

“We think that bacteria were photosynthesising before oxygen was present in the atmosphere,” he said.

Primordial niche

Understanding how arsenic is metabolised by bacteria could help scientists comprehend its damaging effects inside human cells.

Worldwide, 144 million people are exposed to toxic levels of arsenic in their drinking water.

It enters the body’s cells by diffusion; and once inside, it disrupts how they function by binding to their machinery, inactivating it, and disrupting the way energy is transported.

Long-term exposure can lead to skin disease and kidney and bladder cancer, and it is thought to stunt the intellectual development of children.

The most arsenic-contaminated regions are in India, Pakistan, and China, where soluble arsenic in ground waters is above the World Health Organization’s (WHO) suggested maximum safe level of 10 parts per billion.

:: Read original here ::