Since the 1940s, antibiotics have helped people recover from diseases, stop the spread of infectious diseases and prevent further complications. Antibiotics are known to kill or slow down the growth rate of bacteria. Scientists have found out that many legumes contain helpful bacteria in roots called nitrogen fixing bacteria.
In plants, the roots have most of the nutrients including bacteria that transforms into a usable form for the plant. Nitrogen fixing bacteria in plants assist in converting nitrogen to a useable form for the plants in the soil.
The bacteria helps the plants grow therefore the farmers don’t have to add fertilizer with nitrogen. Without this bacteria, plants would not be able to make amino acids needed for the cells for the plant to grow. Like plants, humans benefit from certain bacteria in the body as well.
Antibiotics have been used to prevent diseases in plants and vegetables. Around 40 drugs have been tested for diseases on plants, but only 10 drugs are used on a commercial level by people.
The most used antibiotics in plants are oxytetracycline and streptomycin.
Streptomycin binds to ribosomes and promote synthesis of proteins. It’s more commonly used on apple and pear trees. It is administered to pear and apple trees to control the spread of fire blight, a contagious disease that affect apples and pears that can kill the plant. Fire blight can cause darkened leaves, dried fruits or dead branches. At high doses, the antibiotic can be poisonous to plants. Also, streptomycin can only be used on the surface of the plant because it can be phytotoxic to plants if injected.
The second drug, oxytetracycline, is used on plants throughout the United States. Like streptomycin, oxytetracycline promotes the synthesis of proteins as well and binds to the ribosomes. Oxytetracycline is commonly administered to peaches and nectarines to control the spread of fire blight. However, it has to be applied before rain to prevent the growth on the bacteria on stigmas because it inhibits growth and cannot kill preexisting populations. It is to be used internally by injecting the antibiotic into the trunk of the plant, not on the surface. Oxytetracycline also slows down the growth of a pathogen, but less effective than streptomycin.
Antibiotic use is regulated by the Environmental Protection Agency (EPA) for testing plants. Approval for the use of the antibiotic does not depend on how well the antibiotic controls the bacterial diseases. During testing, the toxicity is tested and how it may affect plants, insects or other organisms in the ecosystem are factored into the approval.
A common bacterial disease in plants is fire blight. If a plant has fire blight, the crop will have no value and certain parts of the plants starts dying. Fire blight commonly appears in apples, pears and blossom trees. In an orchard, fire blight could show little signs in one year, but as the years go on it can spread to other trees. This causes farmers great loss and many countries are taking an effort to destroy trees to stop the spread.
Antibiotics act as a barrier to pathogens on the surface. While streptomycin is used on the surface, it can kill pathogens on the surface of the plant. Oxytetracycline does not kill off pathogens and is less effective. Streptomycin is active for 3 days while oxytetracycline is active for 1 day.