Dutch and Australian scientists have found the "missing" bacterium thought responsible for helping to clean up high ammonia emissions in waste water.
The discovery of the bacterium which can survive without oxygen could solve a riddle puzzling scientists for many years.
"This is the first bacterium in its group thought to have a potential significant economic value," University of Queensland research team member Dr John Fuerst said.
The discovery was reported in the July 29 issue of prestigious scientific magazine Nature. It was made by researchers at the Delft University of Technology, the University of Queensland and Netherlands Institute for Sea Research.
UQ research team members Dr John Fuerst and Dr Richard Webb of the Microbiology and Parasitology Department and Centre for Microscopy and Microanalysis were approached by the Dutch group because of their international expertise in planctomycetes, an unusual and distinctive group of organisms to which the new mystery bacterium belongs.
The UQ team had previously discovered important differences in cell organisation characteristic of the planctomycetes, including a membrane-bounded cell nucleus.
Dr Fuerst said the new work reported in Nature related to the Dutch research group's interest in removing high ammonia emissions from wastewater by innovative processes.
"While it is known that organisms can oxidise ammonia, they normally need the presence of oxygen to do that. Our Dutch colleague's process is unique because in their bioreactors ammonia oxidisation is occuring without oxygen. They wanted to pinpoint the organism responsible," he said.
Dr Fuerst said many densely populated countries faced environmental problems associated with high ammonia emissions, because of the increased use of chemical fertilizers in agriculture.
"Nitrogen is difficult to remove from wastewater and can lead to eutrophication, the undesirable enrichment of rivers and lakes, and this can stimulate bacterial growth, algal blooms and depletion of oxygen in the water," he said.
Dr Fuerst said microbiologists had predicted that a bacterium was responsible for a process known as anammox in which ammonia nitrogen is removed from wastewater in the absence of oxygen and converted into nitrogen gas. The anammox process has been known for the past 10 years, but has resisted meaningful microbiological characterisation.
The researchers did not think a planctomycete bacterium would be involved in the wastewater process. Only a few representatives of the unusual bacterial group had been found in nature and so they were considered of limited environmental importance.
Using sophisticated electron microscopy and molecular microbial techniques, the researchers examined the annamox biomass and were surprised to find membrane-bounded structures in the cell characteristic of planctomycetes. They also found crater-like structures on the cell surface which are also exclusive to planctomycetes. DNA sequencing revealed the bacterium had a distinctive DNA signature defining the organism as a member of the planctomycetes.
"Until now, bacteria capable of oxidizing ammonia in the absence of oxygen had never been found but were predicted to exist and were known as lithotrophs missing from nature," Dr Fuerst said. "This newly discovered bacterium appears to use ammonia as an energy source and carbon dioxide as its sole source of carbon."
The international research group reported the discovery of the missing lithotroph and identified it as a new member of the planctomycetes. By identifying the bacterium responsible for anaerobic ammonia removal, it is now possible to look for this bacterium in natural habitats such as seawater, freshwater and soils.
The researchers believe these mystery organisms once harnessed might provide mankind with a powerful tool for cleaning up unwanted ammonia nitrogen from the environment.
The Queensland researchers are investigating the function of the cell compartments in these organisms in relation to a structural model which will fit all known members of the planctomycetes. In Australia, the planctomycete research has attracted large grant funding from the Australian Research Council.
Research team members are: Delft University of Technology - Marc Strous, Evelien Kramer, Susanne Longemann, Katinka van de Pas-Schoonen, J. Gijs Kuenen and Mike Jetten; University of Queensland - John Fuerst and Richard Webb; Netherlands Institute for Sea Research - Gerard Muyzer.
Pix of Dr Webb (left) and Dr Fuerst and a budding cell of the newly discovered planctomycete bacterium showing internal compartments are available for downloading from the Bacterium folder on the UQ ftp site: http://photos.cc.uq.edu.au/
Media: Further information: Dr John Fuerst telephone 07 3365 4643 or Dr Rick Webb telephone 07 3365 1138 email: j.fuerst@biosci.uq.edu.au, or webb@biosci.uq.edu.au
