The study describes the isolation and characterization of *Nitrososphaera viennensis*, an ammonia-oxidizing archaeon from soil. This archaeon, affiliated with group 1.1b of Thaumarchaeota, can grow on ammonia or urea as an energy source and tolerates higher ammonia concentrations compared to the marine isolate *Nitrosopumilus maritimus*. Surprisingly, while it can grow chemolithoautotrophically, significant growth rates are achieved only when low amounts of pyruvate are added or when grown in coculture with bacteria. The findings expand the metabolic spectrum of ammonia-oxidizing archaea and provide insights into their ecological roles and carbon assimilation mechanisms. The study highlights the importance of obtaining pure cultures to understand the growth requirements and metabolic strategies of these organisms.The study describes the isolation and characterization of *Nitrososphaera viennensis*, an ammonia-oxidizing archaeon from soil. This archaeon, affiliated with group 1.1b of Thaumarchaeota, can grow on ammonia or urea as an energy source and tolerates higher ammonia concentrations compared to the marine isolate *Nitrosopumilus maritimus*. Surprisingly, while it can grow chemolithoautotrophically, significant growth rates are achieved only when low amounts of pyruvate are added or when grown in coculture with bacteria. The findings expand the metabolic spectrum of ammonia-oxidizing archaea and provide insights into their ecological roles and carbon assimilation mechanisms. The study highlights the importance of obtaining pure cultures to understand the growth requirements and metabolic strategies of these organisms.