Engineered bacterial strains could fertilize crops, reduce waterways
pollution

Date:
February 17, 2022
Source:
American Society for Microbiology
Summary:
Researchers have engineered strains of the ubiquitous,
nitrogen-fixing soil bacterium Azotobacter vinelandii to produce
ammonia and excrete it at high concentrations, transferring it
into crop plants in lieu of conventional chemical fertilizers.



FULL STORY ========================================================================== Researchers from Washington State University have engineered strains of
the ubiquitous, nitrogen-fixing soil bacterium Azotobacter vinelandiito
produce ammonia and excrete it at high concentrations, transferring it
into crop plants in lieu of conventional chemical fertilizers.


==========================================================================
"We presented conclusive evidence that ammonia released is transferred to
the rice plants," said Florence Mus, Ph.D., assistant research professor, Institute of Biological Chemistry, Washington State University. "Our
unique approach aims to provide new solutions to the challenge of
replacing industrial fertilizers with custom-made bacteria." In other
words, this approach could mitigate a major source of environmental
pollution. The research is published in Applied and Environmental
Microbiology, a journal of the American Society for Microbiology.

The investigators used gene editing techniques to engineer A.vinlandiito produce ammonia at a constant level, regardless of environmental
conditions surrounding the bacteria, and to excrete it at concentrations
high enough to effectively fertilize crops.

The use of gene editing techniques in lieu of inserting transgenes into
the A.vinlandii genome allowed regulatory requirements to be avoided
that would have made the development process slower, and more difficult
and expensive.

The scientific motivation for the research was an interest in better understanding nitrogen fixation -- that is, the chemical processes by
which atmospheric nitrogen is assimilated into organic compounds as
part of the nitrogen cycle. "Our work helps provide a more complete, fundamental understanding of the factors that underpin gene expression
in a model nitrogen fixing microorganism and defines the biochemistry
that brings about ammonia excretion in A.vinelandii," said Mus.

The practical motivation for the research was to reduce the major water pollution problems that arise when excess nitrogen fertilizer gets
washed into waterways. This causes algal blooms that deplete oxygen and
kill off fish and other aquatic life, creating "dead zones" in lakes,
rivers and expanses of ocean. The dead zone in the northern Gulf of
Mexico encompasses nearly 6,400 square miles.

To this end, the investigators are designing the bacteria to produce
ammonia at a steady rate. But they expect to be able to design different
groups ofA.vinlandiito produce ammonia at different rates to fit the
needs of different species of crop plants. This would allow all the
ammonia produced to be used by the plants, rather than ending up washed
into waterways.

"Successful widespread adoption of these biofertilizers for farming would reduce pollution, provide sustainable ways of managing the nitrogen cycle
in soil, lower production costs and increase profit margins for farmers
and enhance sustainable food production by improving soil fertility,"
said Mus.

========================================================================== Story Source: Materials provided by
American_Society_for_Microbiology. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Florence Mus, Devanshi Khokhani, April M. MacIntyre, Esther
Rugoli, Ray
Dixon, Jean-Michel Ane', John W. Peters. Genetic determinants
of ammonium excretion in nifL mutants of Azotobacter
vinelandii. Applied and Environmental Microbiology, 2022; DOI:
10.1128/AEM.01876-21 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220217163030.htm

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