Microbes (or microorganisms)
are organisms that are too small to be seen
by the unaided eye. They include bacteria, fungi,
protozoa, microalgae, and viruses.
Microbes live in familiar settings
such as soil, water, food, and animal intestines,
as well as in more extreme settings such as
rocks, glaciers, hot springs, and deep-sea vents.
The wide variety of microbial habitats reflects
an enormous diversity of biochemical and metabolic
traits that have arisen by genetic variation
and natural selection in microbial populations.
Historically, humans have exploited
some of this microbial diversity in the production
of fermented foods such as bread, yogurt, and
cheese. Some soil microbes release nitrogen
that plants need for growth and emit gases that
maintain the critical composition of the Earth's
atmosphere.
Other microbes challenge the
food supply by causing yield-reducing diseases
in food-producing plants and animals. In our
bodies, different microbes help to digest food,
ward off invasive organisms, and engage in skirmishes
and pitched battles with the human immune system
in the give-and-take of the natural disease
process.
A genome is the totality of
genetic material in the DNA of a particular
organism. Genomes differ greatly in size and
sequence across different organisms. Obtaining
the complete genome sequence of a microbe provides
crucial information about its biology, but it
is only the first step toward understanding
a microbe's biological capabilities and modifying
them, if needed, for agricultural purposes.
Microbial biotechnology, enabled
by genome studies, will lead to breakthroughs
such as improved vaccines and better disease-diagnostic
tools, improved microbial agents for biological
control of plant and animal pests, modifications
of plant and animal pathogens for reduced virulence,
development of new industrial catalysts and
fermentation organisms, and development of new
microbial agents for bioremediation of soil
and water contaminated by agricultural runoff.
Microbial genomics and microbial
biotechnology research is critical for advances
in food safety, food security, biotechnology,
value-added products, human nutrition and functional
foods, plant and animal protection, and furthering
fundamental research in the agricultural sciences.
CSREES
has identified four major related research objectives:
Assure that the complete nucleic
acid sequences of high priority beneficial and
detrimental agricultural microorganisms are
available in public databases.
Assure that the agricultural
research community has adequate resources and
facilities available for the functional analysis
of agricultural microbes (for example, expression
array technologies, proteomics, relational databases,
and other bioinformatics tools) so that practical
benefits are not delayed.
Support training and extension
for microbial genomics and its evolving technologies.
Foster U.S. interests through national and international
public and private partnerships in microbial
genomics, and, through such partnerships, facilitate
capacity development in the United States and
abroad that ensures public access and appropriate
use of intellectual property.
Microbial
biotechnology has a variety of useful applications
in agriculture
Assessing and managing environmental
risks from transgenic microorganisms is an important
issue for which scientists have developed research
needs and priorities.
The mapping of microbial genomes
is a key technology to understanding microorganisms
and devising ways to improve their use in agricultural
production, food safety, and bio-based chemicals.
For more, see the Microbial Genomics program
page.
Microbial
Fermentation
For many years, man has been
taking advantage of the activities of millions
of microorganisms found in the soil to improve
agricultural productivity. With the large scale
cultivation of microbes or other single cells,
occurring with or without air - known as microbial
fermentation -man has used naturally occurring
organisms to develop biofertilizers and biopesticides
to assist plant growth and control weeds, pests,
and diseases, respectively.
Many of the microorganisms
that live in the soil actually help plants absorb
more nutrients than they would by themselves.
Plants and these friendly microbes are involved
in "nutrient recycling". The microbes
help the plant to "take up" essential
energy sources. In return, plants donate their
waste byproducts for the microbes to use for
food. Because the microbes have helped plants
digest more nutrients, plants develop stronger
and bigger root systems. The larger the plants'
roots, the more living space and food there
is for the microbes to enjoy.
Scientists use these friendly
microorganisms to develop biofertilizers.
Biofertilizers
Phosphate and nitrogen are
important for plant growth. These compounds
exist naturally in the environment but plants
have a limited ability to extract them. Phosphate
is abundant in the soil but remains mostly bound,
and nitrogen is abundant in the air. Phosphate
plays an important role in crop stress tolerance,
maturity, quality and directly or indirectly,
in nitrogen fixation. If phosphate is not quickly
used by the plant, it becomes locked into the
soil through chemical reactions. This leaves
only a small amount of this vital nutrient available
to the plant. The plant cannot unlock phosphate
by itself.
A fungus called Penicillium
bilaii is the roots' key to unlock phosphate
from the soil. It makes an organic acid which
dissolves the phosphate in the soil so that
the roots can use it. A biofertilizer made from
this organism is applied either by coating seeds
with the fungus (called inoculation), or putting
it directly into the ground where the plant's
roots will live.
The friendly fungus can wrap
itself around the root, and prevent other less
helpful organisms from living there. It has
the first chance to use the plant's byproducts.
This will make the microbe stronger, and able
to convert more phosphate for the roots to use.
With additional phosphate, the plants will be
stronger and more productive.
Another example of an organism
that is used to make biofertilizers is the bacterium
Rhizobium. This bacterium lives on
the plant's roots in cell collections called
nodules. The nodules are biological
factories that can take nitrogen out of the
air and convert it into an organic form that
the plant can use. Because the bacteria live
within the roots, it transfers the nutrient
directly into the plant.
This fertilization method has
been designed by nature. With a large population
of the friendly bacteria on its roots, the legume
can use naturally-occurring nitrogen instead
of the expensive traditional nitrogen fertilizer.
Biofertilizers help plants
use all of the food available in the soil and
air thus allowing farmers to reduce the amount
of chemical fertilizers they use. This helps
preserve the environment for the generations
to come.
NitroPlus, Bio-N and BIO-Fix
are some Philippine examples of bio fertilizers
that utilize the ability of microorganisms like
rhizobia to fix free nitrogen. Other products
like Mycogroe and Mykovam help plants absorb
water and phosphorus from the soil. The mycorrhizal
fungi that colonizes the roots of plants prevent
further infections by pathogens and make plants
more tolerant to drought and heavy metals. BIO-Quick,
a composting inoculum, helps hasten the decomposition
of farm and agro-industrial wastes by as much
as 80%.
Biopesticides
As we all know, there are also
microorganisms found in the soil that are not
so friendly to plants. These pathogens can cause
extreme disease or damage to the plant. As with
friendly microorganisms, scientists have developed
biological "tools" which use these
disease-causing microbes to control weeds and
pests naturally.
Bioherbicides
Weeds are a constant problem
for farmers. They not only compete with crops
for water, nutrients, sunlight, and space but
also harbor insect and disease pests; clog irrigation
and drainage systems; undermine crop quality;
and deposit weed seeds into crop harvests. If
left uncontrolled, weeds can reduce crop yields
significantly.
Farmers fight weeds with tillage,
hand weeding, synthetic herbicides, or typically
a combination of all techniques. Unfortunately,
tillage leaves valuable topsoil exposed to wind
and water erosion, a serious long-term consequence
for the environment. For this reason, more and
more farmers prefer reduced or no-till methods
of farming.
Similarly, many have argued
that the heavy use of synthetic herbicides has
led to groundwater contaminations, death of
several wildlife species and has also been attributed
to various human and animal illnesses.
The use of bioherbicides is
another way of controlling weeds without environmental
hazards posed by synthetic herbicides. Bioherbicides
are made up of microorganisms (e.g. bacteria,
viruses, fungi) and certain insects (e.g. parasitic
wasps, painted lady butterfly) that can target
very specific weeds. The microbes possess invasive
genes that can attack the defense genes of the
weeds, thereby killing it.
The better understanding of
the genes of both microorganisms and plants
has allowed scientists to isolate microbes (pathogens)
whose genes match particular weeds and are effective
in causing a fatal disease in those weeds. Bioherbicides
deliver more of these pathogens to the fields.
They are sent when the weeds are most susceptible
to illness.
The genes of disease-causing
pathogens are very specific. The microbe's genes
give it particular techniques to overcome the
unique defenses of one type of plant. They instruct
the microbe to attack only the one plant species
it can successfully infect. The invasion genes
of the pathogen have to match the defense genes
of the plant. Then the microbe knows it can
successfully begin its attack on this one particular
type of plant. The matching gene requirement
means that a pathogen is harmless to all plants
except the one weed identified by the microbe's
genetic code.
This selective response makes
bioherbicides very useful because they kill
only certain weed plants that interfere with
crop productivity without damaging the crop
itself. Bioherbicides can target one weed and
leave the rest of the environment unharmed.
The benefit of using bioherbicides
is that it can survive in the environment long
enough for the next growing season where there
will be more weeds to infect. It is cheaper
compared to synthetic pesticides thus could
essentially reduce farming expenses if managed
properly. It is not harmful to the environment
compared to conventional herbicides and will
not affect non-target organisms.
With the advances of genetic
engineering, new generation bioherbicides are
being developed that are more effective against
weeds. Microorganisms are designed to effectively
overcome the weed's defenses. Weeds have a waxy
outer tissue coating the leaves that microorganisms
have to penetrate in order to fully infect the
weeds. Through biotechnology, these microorganisms
will be able to produce the appropriate type
and amount of enzymes to cut through the outer
defenses. Streamlining of the microbe's plant
host specificity will ensure that the weeds
are taken out and not the crops. On the other
hand, microbes can also be made to be effective
against several host weeds and not only to one
type of weed as this can be too expensive to
produce for commercial use.
Bioinsecticides
The science of biotechnology
can also help in developing alternative controls
to synthetic insecticides to fight against insect
pests. Research has found microorganisms in
the soil that will attack fungi, viruses or
bacteria which cause root diseases. Formulas
for coatings on the seed (inoculants) which
carry these beneficial organisms can be developed
to protect the plant during the critical seedling
stage.
While synthetic pesticides
are an invaluable tool for agricultural productivity,
some of them also have their drawbacks: they
are expensive, they are often not foolproof;
they can accumulate in our environment and pollute
our water systems; and they are not species
specific as they can also kill non-target organisms.
Bioinsecticides, on the other
hand, do not persist long in the environment
and have shorter shelf lives; they are effective
in small quantities, safer to humans and animals
compared to synthetic insecticides; they are
very specific, often affecting only a single
species of insect and have a very specific mode
of action; slow in action and the timing of
their application is relatively critical.
Some of these characteristics
however, are seen by critics as a disadvantage.
For example, because most of these bioinsecticide
agents are living organisms, their success is
affected by several factors like temperature,
pH, moisture, UV, soil conditions, and other
microbial competitors present in the environment.
Slow in action means much longer time for it
to eradicate pathogens compared to synthetic
pesticides.
Fungi-based
bioinsecticides
Fungi that cause disease in
some 200 different insects are gaining prominence
as bioinsecticides. One of the earliest to be
discovered in the 1880s is Beauveria bassiana
(Bb), a fungus found worldwide in soils and
plants. Another half a dozen fungi are also
known to have characteristics valuable for insect
control. In China, over two million hectares
are sprayed with Bb annually to control forestry
pests. Since 1993, six new fungal bioinsecticides
have become available in North America and Europe.
Inexpensive fermentation technology
is used to mass produce fungi. Spores are harvested
and packaged so they can be applied to insect-ridden
fields. When the spores are applied, they use
enzymes to break through the outer surface of
the insects' bodies. Once inside, they begin
to grow and eventually cause death.
Bioinsecticides based on Bb
have many advantages. The fungus does not grow
in warm-blooded organisms (such as people),
nor does it survive long in water reservoirs
or rivers. However, its spores can withstand
long periods of dryness and other harsh environmental
conditions. Studies to date have shown that
the fungus also does not hurt plants and becomes
inactivated by the sun's ultraviolet rays in
one to eight weeks.
Fungal agents are viewed by
some researchers as having the best potential
for long-term insect control. This is because
these bioinsecticides attack in a variety of
ways at once, making it very difficult for insects
to develop resistance.
Virus-Based
Bioinsecticides
A group of virus-based insecticides
that scientists are testing are the rod-shaped
baculoviruses. Baculoviruses affect insect pests
like corn borers, potato beetles, flea beetles
and aphids. One particular strain is being used
as a control agent for bertha army worms, which
attack canola, flax, and vegetable crops. During
the worst years of the infestation in the early
1980's in Canada, they cleaned out over one
million hectares of prairie crops. In the past,
farmers used chemical insecticides to control
these pests. But Bertha army worms attack crops
while in the larval (caterpillar) stage. Traditional
insecticides do not affect the worm until after
it has reached this stage and by then much of
the damage has been done.
Source:
http://www.csrees.usda.gov/nea/biotech/in_focus/biotechnology_if_microbial.html