Ice-minus bacteria
Encyclopedia
Ice-minus bacteria is a common name given to a variant of the common bacterium Pseudomonas syringae
(P. syringae). This strain of P. syringae lacks the ability to produce a certain surface protein
, usually found on wild-type P. syringae. The "ice-plus" protein (Ina protein, "Ice nucleation-active" protein) found on the outer bacterial cell wall
acts as the nucleating centers
for ice crystals. This facilitates ice formation, hence the designation "ice-plus." The ice-minus variant of P. syringae is a mutant
, lacking the gene
responsible for ice-nucleating surface protein production. This lack of surface protein provides a less favorable environment for ice formation. Both strains of P. syringae occur naturally, but recombinant DNA technology has allowed for the synthetic removal or alteration of specific genes, enabling the creation of the ice-minus strain. Modifying P. syringae may have unexpected consequences for climate. A study has shown that its ice nucleating proteins may play an important part in causing ice crystals to form in clouds. If humans increase the frequency of bacteria lacking these proteins then it could potentially affect rainfall.
The success of the agricultural world
is heavily dependent on the weather. Cold weather conditions are directly responsible for the appearance of frost
on plants and most importantly, crops. In the United States
alone, it has been estimated that frost accounts for approximately $1 billion in crop damage each year. As P. syringae commonly inhabits plant surfaces, its ice nucleating nature incites frost development, freezing the bud
s of the plant and destroying the occurring crop. The introduction of an ice-minus strain of P. syringae to the surface of plants would incur competition between the strains. Should the ice-minus strain win out, the ice nucleate provided by P. syringae would no longer be present, lowering the level of frost development on plant surfaces at normal water freezing temperature (0oC). Even if the ice-minus strain does not win out, the amount of ice nucleate present from ice-plus P. syringae would be reduced due to competition. Decreased levels of frost generation at normal water freezing temperature would translate into a lowered quantity of crops lost due to frost damage, rendering higher crop yields overall.
was the first to notice a connection between bacteria and frost damage. In 1961, Paul Hoppe studied a corn fungus
by grinding up infected leaves each season, then applying the powder to test corn for the following season to track the disease. A surprise frost occurred that year, leaving peculiar results. Only plants infected with the diseased powder incurred frost damage, leaving healthy plants unfrozen. This phenomenon would baffle scientists until graduate student Stephen Lindow of the University of Wisconsin–Madison
with D.C. Arny and C. Upper found a bacterium in the dried leaf powder in the early 1970s. Dr. Lindow, now a plant pathologist at the University of California-Berkeley
, found that when this particular bacterium was introduced to plants where it is originally absent, the plants became very vulnerable to frost damage. He would go on to identify the bacterium as P. syringae, investigate P. syringaes role in ice nucleation and in 1977, discover the mutant ice-minus strain. He was later successful at developing the ice-minus strain of P. syringae through recombinant DNA technology as well.
In 1983, Advanced Genetic Sciences (AGS) obtained U.S. government authorization to perform field tests with the ice-minus strain of P. syringae, but environmental groups and protestors delayed the field tests for four years with legal challenges. In 1987, the ice-minus strain of P. syringae became the first genetically modified organism (GMO)
to be released into the environment . A strawberry field in California
was sprayed with the ice-minus strain of P. syringae just before a frost in 1987. The results were promising, showing lowered frost damage to the treated plants, but the data was in suspect as environment activists destroyed some of the plants. Dr. Lindow also conducted an experiment on a crop of potato seedlings sprayed with ice-minus P. syringae. He was successful in protecting the potato crop from frost damage with a strain of ice-minus P. syringae.
was considered to be very controversial. The controversy primarily revolved around fears of introducing new organisms that may permanently disrupt the ecosystem
.
Pseudomonas syringae
Pseudomonas syringae is a rod shaped, Gram-negative bacterium with polar flagella. It is a plant pathogen which can infect a wide range of plant species, and exists as over 50 different pathovars, all of which are available to legitimate researches via international culture collections such as the...
(P. syringae). This strain of P. syringae lacks the ability to produce a certain surface protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, usually found on wild-type P. syringae. The "ice-plus" protein (Ina protein, "Ice nucleation-active" protein) found on the outer bacterial cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
acts as the nucleating centers
Nucleation
Nucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form by way of nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation...
for ice crystals. This facilitates ice formation, hence the designation "ice-plus." The ice-minus variant of P. syringae is a mutant
Mutant
In biology and especially genetics, a mutant is an individual, organism, or new genetic character, arising or resulting from an instance of mutation, which is a base-pair sequence change within the DNA of a gene or chromosome of an organism resulting in the creation of a new character or trait not...
, lacking the gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
responsible for ice-nucleating surface protein production. This lack of surface protein provides a less favorable environment for ice formation. Both strains of P. syringae occur naturally, but recombinant DNA technology has allowed for the synthetic removal or alteration of specific genes, enabling the creation of the ice-minus strain. Modifying P. syringae may have unexpected consequences for climate. A study has shown that its ice nucleating proteins may play an important part in causing ice crystals to form in clouds. If humans increase the frequency of bacteria lacking these proteins then it could potentially affect rainfall.
Production
To systematically create the ice-minus strain of P. syringae, its ice-forming gene must be isolated, amplified, deactivated and reintroduced into P. syringae bacterium. The following steps are often used to isolate and generate ice-minus strains of P. syringae:- Digest P. syringaes DNADNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
with restriction enzymes. - Insert the individual DNA pieces into a plasmidPlasmidIn microbiology and genetics, a plasmid is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. They are double-stranded and, in many cases, circular...
. Pieces will insert randomly, allowing for different variations of recombinant DNA to be produced. - Transform the bacterium Escherichia coliEscherichia coliEscherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
(E.coli) with the recombinant plasmid. The plasmid will be taken in by the bacteria, rendering it part of the organism's DNA. - Identify the ice-gene from the numerous newly developed E. coli recombinants. Recombinant E. coli with the ice-gene will possess the ice-nucleating phenotypePhenotypeA phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
, these will be "ice-plus." - With the ice nucleating recombinant identified, amplify the ice gene with techniques such as polymerase chain reactions (PCR)Polymerase chain reactionThe polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
. - Create mutant clones of the ice gene through the introduction of mutagenic agentsMutagenIn genetics, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are therefore also likely to be carcinogens...
such as UV radiationUltravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
to inactivate the ice gene, creating the "ice-minus" gene. - Repeat previous steps (insert gene into plasmid, transform E. coli, identify recombinants) with the newly created mutant clones to identify the bacteria with the ice-minus gene. They will possess the desired ice-minus phenotype.
- Insert the ice-minus gene into normal, ice-plus P. syringae bacterium.
- Allow recombination to take place, rendering both ice-minus and ice-plus strains of P. syringae.
Economic importance
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
is heavily dependent on the weather. Cold weather conditions are directly responsible for the appearance of frost
Frost
Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water. Frost crystals' size differ depending on time and water vapour available. Frost is also usually...
on plants and most importantly, crops. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
alone, it has been estimated that frost accounts for approximately $1 billion in crop damage each year. As P. syringae commonly inhabits plant surfaces, its ice nucleating nature incites frost development, freezing the bud
Bud
In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be specialized to develop flowers or short shoots, or may have...
s of the plant and destroying the occurring crop. The introduction of an ice-minus strain of P. syringae to the surface of plants would incur competition between the strains. Should the ice-minus strain win out, the ice nucleate provided by P. syringae would no longer be present, lowering the level of frost development on plant surfaces at normal water freezing temperature (0oC). Even if the ice-minus strain does not win out, the amount of ice nucleate present from ice-plus P. syringae would be reduced due to competition. Decreased levels of frost generation at normal water freezing temperature would translate into a lowered quantity of crops lost due to frost damage, rendering higher crop yields overall.
Historical perspective
P. E. Hoppe of the U.S. Department of AgricultureUnited States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
was the first to notice a connection between bacteria and frost damage. In 1961, Paul Hoppe studied a corn fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
by grinding up infected leaves each season, then applying the powder to test corn for the following season to track the disease. A surprise frost occurred that year, leaving peculiar results. Only plants infected with the diseased powder incurred frost damage, leaving healthy plants unfrozen. This phenomenon would baffle scientists until graduate student Stephen Lindow of the University of Wisconsin–Madison
University of Wisconsin–Madison
The University of Wisconsin–Madison is a public research university located in Madison, Wisconsin, United States. Founded in 1848, UW–Madison is the flagship campus of the University of Wisconsin System. It became a land-grant institution in 1866...
with D.C. Arny and C. Upper found a bacterium in the dried leaf powder in the early 1970s. Dr. Lindow, now a plant pathologist at the University of California-Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
, found that when this particular bacterium was introduced to plants where it is originally absent, the plants became very vulnerable to frost damage. He would go on to identify the bacterium as P. syringae, investigate P. syringaes role in ice nucleation and in 1977, discover the mutant ice-minus strain. He was later successful at developing the ice-minus strain of P. syringae through recombinant DNA technology as well.
In 1983, Advanced Genetic Sciences (AGS) obtained U.S. government authorization to perform field tests with the ice-minus strain of P. syringae, but environmental groups and protestors delayed the field tests for four years with legal challenges. In 1987, the ice-minus strain of P. syringae became the first genetically modified organism (GMO)
Genetically modified organism
A genetically modified organism or genetically engineered organism is an organism whose genetic material has been altered using genetic engineering techniques. These techniques, generally known as recombinant DNA technology, use DNA molecules from different sources, which are combined into one...
to be released into the environment . A strawberry field in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
was sprayed with the ice-minus strain of P. syringae just before a frost in 1987. The results were promising, showing lowered frost damage to the treated plants, but the data was in suspect as environment activists destroyed some of the plants. Dr. Lindow also conducted an experiment on a crop of potato seedlings sprayed with ice-minus P. syringae. He was successful in protecting the potato crop from frost damage with a strain of ice-minus P. syringae.
Controversy
At the time of Dr. Lindow's work on ice-minus P. syringae, genetic engineeringGenetic engineering
Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genome using modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest...
was considered to be very controversial. The controversy primarily revolved around fears of introducing new organisms that may permanently disrupt the ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
.
External links
- P. syringae genomic information from Cornell University's Pseudomonas-Plant Interaction Project
- Genetically modified organisms and food information from the Oak Ridge National Laboratory
- News and information about genetically modified organisms and food from the Food and Agriculture Organization of the United Nations