Each year on the Fourth of July, millions of American flock to their local parks in the dark to watch firework celebrations. But we’re not the only species that revels in these illuminations. As it turns out, a small set of bacteria species can thrive on ingredients used to generate these pyrotechnic displays, specifically compounds in the fireworks called perchlorates. And now researchers have found that this trait is not unique to the bacteria kingdom but that it extends into the archaeal domain as well.
But over the last twenty years, increasing evidence has been found that, in prehistoric times, perchlorates were continuously produced in our atmosphere and rained down on the Earth quite regularly; however, natural perchlorate production eventually declined dramatically.
“In very arid areas on Earth, you can measure the perchlorate to some extent, and all the other places it’s gone,” said Martin Liebensteiner, a researcher at the Wareningen University in the Netherlands. “So we started wondering if this could have been due to microbial utilization?”
Previously, researchers have found that a handful of bacteria species are capable of reducing chlorates and perchlorates. But to explain the disappearance of these compounds from the atmosphere, it seemed likely that more species would need to be capable of this reductive process.
And in a paper recently published in Science (1), Liebensteiner and colleagues began to expand the list of perchlorate-reducing organisms, with the addition of the archaeon Archaeoglobus fulgidus, which has a separate evolutionary history from its perchlorate-reducing bacteria counterparts.
A. fulgidus is a single-celled microorganism that lives in deep sea vents. A hyperthermophile, it is perfectly comfortable at 80 degrees Celsius (about 176 degrees Fahrenheit). Not only does this species not require oxygen to live—oxygen is actually deadly to it. Instead, A. fulgidus metabolism depends on sulfur-based compounds.
To show that the microbe did indeed reduce perchlorate, Liebensteiner and colleagues looked at its genome and proteome. But first they had to grow this hyperthermophile in the laboratory, which proved challenging. “They rely on these exotic conditions such as high temperature, extremely salty conditions, and on certain pressures, so this is actually for us hostile environment, but they like it,” said Liebensteiner.
Once Liebensteiner and his team found the proper conditions to grow A. fulgidus, they began to introduce perchlorates into the microbe’s environment to see if it would reduce the compounds. Indeed it did, but unlike its bacterial counterparts, A. fulgidus does not produce oxygen when reducing perchlorates. Instead, it produces sulfates.
“It has a strange new alternative pathway of reducing perchlorates, a new variant of the perchlorate reduction pathway found only previously in bacteria,” said Liebensteiner.
1. Liebensteiner, M. G., M. W. H. Pinkse, P. J. Schaap, A. J. M. Stams, and B. P. Lomans. 2013. Archaeal (Per)Chlorate reduction at high temperature: An interplay of biotic and abiotic reactions. Science 340(6128):85-87.