GROWTH OF NITROSOMONAS-EUROPAEA ON HYDROXYLAMINE

Hydroxylamine is an intermediate in the oxidation of ammonia to nitrit e, but until now it has not been possible to grow Nitrosomonas europae a on hydroxylamine. This study demonstrates that cells of N. europaea are capable of growing mixotrophically on ammonia and hydroxylamine. T he molar growth yield on hydroxylamine (4.74 g mol(-1) at a growth rat e of 0.03 h(-1)) was higher than expected. Aerobically growing cells o f N. europaea oxidized ammonia to nitrite with little loss of inorgani c nitrogen, while significant inorganic nitrogen losses occurred when cells were growing mixotrophically on ammonia and hydroxylamine. In th e absence of oxygen, hydroxylamine was oxidized with nitrite as electr on acceptor, while nitrous oxide was produced. Anaerobic growth of N. europaea on ammonium, hydroxylamine and nitrite could not be observed at growth rates of 0.03 h(-1) and 0.01 h(-1).