01 September 2008

Arsenic breathers

Bacteria are the ultimate extremophiles being able to survive and indeed thrive in the most inhospitable of conditions. According to this ABC story scientists have found some living in hot springs that uses instead of oxygen for photosynthesis. The new organisms, found floating in Mono Lake in California, are reported in today's issue of the journal Science.


Since the 1990s, scientists have discovered about 20 species of bizarre bacteria that "breathe" arsenic. They are typically found in environments where oxygen is scarce and have been forced to survive on whatever strange substance is easily available. "Just like you and I inhale oxygen and breathe out carbon dioxide, these bugs breathe in Arsenic (III) and breathe out Arsenic (V)," said researcher Ronald Oremland.


Arsenic (III) is the most poisonous form of the element, because it acts much like phosphorous. Most life on Earth needs phosphorous to build the molecule called ATP, which supplies cells with energy. Arsenic can substitute for phosphorous and upset the ATP molecule, essentially starving cells to death.


In the arsenic-rich, oxygen-poor waters of Mono Lake, Oremland and team found that bacteria turn the lethal toxin to their advantage through photosynthesis. With the help of sunlight, the microbes oxidise Arsenic (III) ions into Arsenic (V) ions, stripping away electrons in the process. The electrons are then used as the energetic push needed to build ATP.


More than a mere biological oddity, the discovery adds weight to Oremland's theory that the bacteria's ability evolved billions of years ago, when the first life was just getting started on earth. At the time, the planet's oceans were devoid of oxygen, but hydrothermal vents spewed elements such as sulphur, iron and arsenic into the water column. In this ancient stew, arsenic may have been an important nutrient to life. The life-forms would have used whatever they could to survive these noxious waters, and sunlight and arsenic were probably plentiful. As the life-forms found they could make a living off of these odd bedfellows, one of the first forms of photosynthesis was born.


Modern photosynthesis is thought to have evolved between 2.3 and 2.7 billion years ago. The arsenic-based form may be much older.


File this one under fascinating!

9 comments:

Welshcakes Limoncello said...

It IS fascinating, jams, and you have written it in such a way that I can understand it - I usually give up on scientific stuff.

jams o donnell said...

I largely used the ABC article which was very readable Welshcakes!

SACKERSON said...

Yes, that is interesting. And according to QI the other night, arsenic was also used as a performance-enhancing drug by marathon runners in the 1904 Olympics.

Nunyaa said...

Serious, if I didnt come here and read this I would not of known, how odd yet as you say, interesting.

jams o donnell said...

Wow Sackerson... I wonder how many survived to cross the finishing line!

I must admit I gaze in awe at life Nunyaa

CalumCarr said...

When I was doing my PhD there was a post-doc in the lab working on a group of arsenic compounds called arsoles - pronounced arzoles.

jams o donnell said...

Haha Callum I remember being amused when I was an undergrad doing my main research project in my final year. A post grad had put a copy of an article about Arsoles on his wall. Beign someone who laoughs at fart jokes I guffawed!!

Lord James Bigglesworth said...

What next? Bacteria getting their fix of arsenic - really.

jams o donnell said...

Bacteria these day. When I was a young unicellular organism I gould have got a flick of the flagellum if I had tried arsenic!