Land and Water Link
December 2004
 Probing
living earth
In balanced, healthy ecosystems, soil is teeming with
life. Abundant soil microbes perform a myriad of chemical transformations
to keep mineral and organic nutrients cycling through the system. Without
them, the ecosystem would become pretty sick, pretty quickly.
Rather than trying to isolate, identify and study the
individual components of this rich brew, scientists can now consider the
soil as a single living organism, where the entire spectrum of microbial
inhabitants operate as a collective, with a single genome. Using the tools
of biotechnology (like gene probes) it is possible to identify the potential
for a given soil to perform key metabolic functions.
This is one feature of a ground-breaking approach taken
by environmental biotechnologist Dr Steve Rogers and his group at CSIRO
Land and Water, in collaboration with Dr Matt Colloff from CSIRO Entomology
(see Land and Water Link, May 2002).
As Dr Rogers explains, ‘You can actually address
soil nutrient management or natural resource management issues with these
tools and very quickly get an answer, as compared to traditional microbiology
techniques.’
In just six weeks, the research team helped solve a puzzle
that had been vexing scientists at the University of Alaska for more than
20 years.
‘There was a big gap in their understanding of where
the nitrogen in the system was coming from. They found more nitrogen in
the trees (primary production) than they could account for in the system.
So there was nitrogen coming from somewhere that was getting into the
trees, but they couldn’t understand where it was coming from’,
says Dr Rogers.
Then Professor Rich Boone from the Institute of Arctic
Biology at the University of Alaska Fairbanks invited Dr Rogers to participate
in a collaborative project, funded by the University’s ‘Experimental
Program to Stimulate Competitive Research’.
‘We went in to this great place called Bonanza Creek
– a long-term arctic boreal forest ecological research site of the
US National Science Foundation – and used our probes to look at
the biology, the bacteria involved in fixing nitrogen.’
‘Nitrogen fixers’ perform a critical role
in both natural and agricultural systems. But they had not previously
been implicated in the nitrogen cycle of these arctic forests.
‘With the use of these probes, we were the first
to show that there are lots of free-living nitrogen fixers in the system.
These are bugs that can take nitrogen out of the atmosphere and put it
into the soil’, says Dr Rogers.
There are some interesting parallels between the forests
of Northern Alaska and Australian native forests, particularly temperate
and desert systems. Both are characterised by very low rainfall –
or precipitation, as the majority falls as snow in Alaska – and
consequently, relatively short periods of biological activity. In Alaska
the microbes get going in summer, when the snow melts. In Australia it’s
winter, with the rains. ‘So you can see they’re very similar
in terms of the climatic factors that drive how they function biologically’,
says Dr Rogers.
And the bugs responsible for all these nitrogen transformations
are also the same in Alaskan and Australian soils. ‘Their genes
are the same, otherwise the technique wouldn’t work’, he says.
By developing a ‘biogeochemical’ understanding
of how our landscapes function, Dr Rogers hopes to ultimately produce
diagnostic tools that can assess ecosystem functions and health.
 The
science of biogeochemistry is already being applied to a number of other
environmental management issues such as the relationship between pasture
management and soil function, the impact of salt on sediment nitrification,
the role of micro-organisms in the formation of acid sulphate soils, and
the impact of soil heavy-metal contaminants on microbial function.
It is easy to imagine valuable uses for new commercial
tools that can simplify these tests and take them out of the laboratory
into the field. For example, they might be used for assessing land management
actions for positive or negative effects over time, or for following the
fate and activities of bioremediation agents added to contaminated soils
to perform particular clean-up reactions.
In the artic forests of Northern Alaska the team has shown
there is the potential for free living nitrogen fixation and this appears
to be an important part of the system. ‘So if there is a fire or
a change in the management regime, or even global warming, we need to
understand how that will impact on these groups of organisms’, explains
Dr Rogers. ‘Now we can use the molecular tools to monitor the situation.'
CSIRO contact:
Dr Steve Rogers
Ph: +61-8-8303 8407
By Clare Peddie
|
