Ammonia-oxidizing bacteria are key players in the nitrogen cycle found both in water and on land. For decades, researchers believed that only bacteria could break down ammonia in the presence of oxygen, but several studies have since disproved that theory. Recent work now suggests that ammonia-oxidizing archaea such as those called Crenarcheota are widespread in water columns and sediments.
Photo: Cells from culture HB-F7 with Crenarchaea (green) and bacteria (purple) visualized by
fluorescent in situ hybridization with an archaeal-specific probe, courtesy of Annika Mosier
Crenarchaeota is an ammonia-oxidizing archaea found in both marine and freshwater environments. Marine Creneoarcheota are so plentiful that by some estimates they account for roughly 20 percent of all the prokaryotes ¾ organisms that lack a cell nucleus ¾ in waters around the world. Due to their sheer numbers, some researchers estimate Crenarcheota’s contribution to dark carbon fixation in the ocean to be significant.
The archaea were once thought to be composed solely of extremophiles but some Crenarcheota have been found in more moderate conditions. And while researchers have been able to isolate a mesophilic, marine representative of Crenarcheota, very little is known of freshwater ammonia-oxidizing archaea. By studying a novel culture of Crenarcheota collected from Huntington Beach, Calif., researchers hope to understand the role of the archaea in global carbon cycle. Additionally, some experiments have shown that Crenarcheota might be useful in cleaning up areas such as several legacy DOE sites involved in nuclear testing that are contaminated with the radioactive material strontium-90.
Principal Investigators: Christopher Francis (Stanford University)
Program: CSP 2009