Lightning May Have Fed Early Life

Wednesday, 15 July 2009

by Michael Reilly Discovery News

Lightning strike leftovers may contain a key to the origins of life (Source: Sheila O'Boyle/User submitted)

A new study suggests tiny pieces of melted earth caused by lightning strikes were crucial in getting life started billions of years ago.

On average, lightning hits the earth's surface 44 times per second.

Where the lightning strikes it leaves glassy veins of melted sand and soil called fulgurites, which are also full of rare forms of phosphorous.

Matthew Pasek and Kristin Block of the University of Arizona in Tucson sampled 10 fulgurites collected from the deserts of Africa and Australia, and from soils around the United States. They found the deposits were rich in phosphite (HPO3) and hypophosphite (H2PO2) ions, two chemicals found almost nowhere else on the planet.

The researchers' work was published yesterday in the journal Nature Geoscience.

Pasek and Block believe lightning forges about two to three tonnes of the compounds each year, barely enough for life to take notice. But modern bacteria still retain the ability to eat phosphite, which may be a holdover from antiquity.

"There is a certain gene that encodes for oxidising phosphite to phosphate. It's all over; it's in many species of soil bacteria, it's in Escherichia coli (E. coli)," Pasek said. "It's hard to tell exactly how old it is, but it's ancient."

Fast food

Billions of years ago, earth was pummeled by meteorites that carried tonnes of phosphite and hypophosphite from outer space. Both compounds dissolve more readily in water than phosphate, making them easy for the first life forms to eat.

Pasek theorises that phosphite and hypophosphite were essential to early microbes.

Later, as organisms came into contact with the abundant phosphate locked away in rocks they changed their diet, but retained the ability to eat the rarer forms.

"This research may be an explanation as to why modern microorganisms continue to have the ability to metabolise these forms of phosphorous," says John Quinn of Queen's University in Belfast.

"Phosphorous was essential to early life, and we have a biological reminder of this today."

Modern life forms are just as dependent on phosphorous as ever. From the lowest bacteria to humans - even viruses - every living thing requires the element to survive.

Our bone structure, our metabolism and DNA, all use the phosphate ion (PO4) as their chemical foundation. About 1% of everything we eat is phosphate.

"It's pretty hard to imagine life without phosphorous," says Pasek.

Source: ABC Science News