WASHINGTON — A scientific tiff went public Friday as the journal Science took the unusual step of publishing challenges to an earlier report about a strange, arsenic- eating bacteria.
The authors of the study stood their ground, saying they consider their interpretation of the research viable.
In the report, published in Science last year, researchers led by Felisa Wolfe-Simon of NASA’s Astrobiology Institute said they discovered bacteria that can substitute arsenic for some of the phosphorous in its diet. While the discovery was made on Earth, they said it shows that life has possibilities beyond the major elements that have been considered essential.
Six major elements have long been considered essential for life — carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Arsenic is toxic mainly because its chemical behavior is so similar to that of phosphorus and some organisms have a hard time telling these elements apart. But once ingested, arsenic is different enough that it can disrupt the body’s chemistry.
The bacteria were discovered in a California lake where there is a high concentration of arsenic, and the researchers concluded that although it grows better with phosphorous, it was able to successfully substitute some arsenic.
In one challenge, Patricia Foster of Indiana University pointed out that bacteria have two systems for assimilating phosphorous. Foster said the researchers inadvertently shut off one system when they grew bacteria in high-arsenic concentrations, increasing the capacity of the other. Wolfe-Simon and colleagues responded that, in that case, a modified form of arsenic would appear and that did not happen.
In another challenge, James Cotner of the University of Minnesota and Edward Hall of the University of Vienna argued that the microbes might simply have been able to live on very low levels of phosphorous. Wolfe-Simon responded that the particular cells Cotner and Hall referred to actually had relatively high phosphorous levels.
