Anammox: Bad luck or the tip of the iceberg

Marc Strous, Ph.D.
Delft University of Technology, The Netherlands

Wednesday, November 3, 1999
3:00 p.m.—Pacific Forum

With the increased use of chemical fertilizers in agriculture, many densely populated countries face environmental problems associated with high ammonia emissions. The anaerobic ammonia oxidation (Anammox) process is one of the most innovative technological advances in the removal of ammonia-nitrogen from wastewater. This new process combines ammonia and nitrite directly into dinitrogen gas. The theoretical possibility of Anammox was recognized as early as 1975. However, bacteria capable of Anammox had never been found and were known as the "lithotrophs missing in nature." Now, we have found this missing lithotroph and identified it as a new, autotrophic member of the Order Planctomycetales, one of the major distinct divisions of the bacteria. The new planctomycete grows extremely slowly, dividing only once every two weeks. Presently, it cannot be cultivated with conventional microbiological techniques. The identification of this bacterium as the one responsible for Anammox is an important contribution to the problem of unculturability. This notion has become central to microbiology since molecular ecology showed that scientists have so far devoted themselves to only a fraction of the naturally occurring microorganisms.

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