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http://www.sciencewa.net.au/3838-glimpses-into-n-cycling-bacteria-give-positive-outlook-for-wa-soils.html

Glimpses into N-cycling bacteria give positive outlook for WA soils
ScienceNetwork WA
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Written by Mary-Anne Romano Monday, 16 January 2012 12:00

WA__Pasture
The research conducted by Dr O’Sullivan and her colleagues has shown
that AOA are important members of the nitrogen-cycling community in
acidic WA pasture soils. Image: Luke Redmond

A WESTERN Australian study into the levels of ammonia-oxidising
archaea (AOA) and ammonia-oxidising bacteria (AOB) in soils is aiding
in the understanding of the nitrogen cycle in agricultural systems.

Postdoctoral fellow Dr Cathryn O’Sullivan, from the CSIRO and fellow
researchers, investigated soils underlying pastures located in the
Harvey-Waroona area in 2009.

According to Dr O’Sullivan, the discovery of ammonia oxidizing archaea
in soil is important as it helps to increase the understanding of
these organisms that control nitrification.

“Research on AOA is still relatively new but as we learn more about
their distribution and their physiology it will help to explain this
important reaction and perhaps offer ways to control it,” she says.

Nitrification involves the conversion of ammonium to nitrate by
soil-living bacteria, with ammonia oxidising microorganisms converting
the ammonium (NH4+) into nitrite (NO2-).

>From here, it is rapidly converted into nitrate (NO3-) by another
group of microorganisms.

This reaction in the nitrogen cycle has both costs and benefits in
agricultural systems, says Dr O’Sullivan.

“Some plants will grow better on nitrate than they do on ammonium so
some nitrification in soils is beneficial as it allows ammonium based
fertilisers to be converted into a form that can be used more
efficiently by some plants but nitrification is also the first step in
several reactions that lead to fertiliser losses.”

The study has also looked at the effect soil pH has on the AOA. Like
several other studies, they found that AOA will grow in acidic and
alkaline soils. AOB on the other hand are generally believed to be
favoured by a neutral pH environment.

The research conducted by Dr O’Sullivan and her colleagues has shown
that AOA are important members of the nitrogen-cycling community in
acidic WA pasture soils.

While this area of soil research is still in its infancy, Dr
O’Sullivan believes this work will help broaden the knowledge of the
organisms that control the nitrogen cycle.

“The cycling of nitrogen through soils and waters, to the atmosphere
and back again is essential to all life and this kind of work helps to
increase our understanding of factors that control the reactions that
make up that cycle,” she says.

The study, ‘Archaeal ammonia oxidisers are abundant in acidic, course
textured Australian soils’ was published earlier this month in the
CSIRO publication Soil Research.