Lightning May Have Helped Feed Early Life

July 13, 2009 -- Lightning strike leftovers may contain a key to the origins of life.

Earth is under fire from a constant barrage of electricity: on average, lightning hits the planet's surface 44 times per second, leaving glassy veins of melted sand and soil called fulgurites scattered across the globe. According to a new study, the deposits are also full of rare forms of phosphorous that may have been crucial in getting life started billions of years ago.

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 tons 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.

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"There is a certain gene that encodes for oxidixing 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."

Billions of years ago, Earth was pummeled by meteorites that carried tons 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 theorizes 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 metabolize these forms of phosphorous," John Quinn of Queen's University in Belfast said. "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 percent of everything we eat is phosphate.

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

Related Links:

HowStuffWorks.com: Phosphorous Cycle

Discovery Earth