What Is a Kanamycin Resistance Gene?

Sarah Parrish

The kanamycin resistance gene (nptII or nptIII) is a string of DNA that allows an organism to produce a protein, conferring resistance to the common antibiotic kanamycin. This gene is often used as a selective marker for exogenous plasmids — plasmids that aren't naturally occurring — in organisms such as bacteria or yeast. This selection agent is also used in plants. Scientists who study genetics or proteomics can select for bacterial colonies that include an inserted gene of interest based on applying kanamycin. Kanamycin will kill every cellular colony that doesn't include cells transcribing and translating the associated resistance gene.

The kanamycin resistance gene can be of great use to scientists who study genetics and proteomics.
The kanamycin resistance gene can be of great use to scientists who study genetics and proteomics.

The kanamycin resistance gene has natural origins and is found in Streptomyces kanamyceticus, a bacteria that is able to produce an enzyme that breaks down the kanamycin antibiotic before the antibiotic can destroy the bacteria. Any cell that can read this gene and transcribe the resultant enzyme will have a resistance to kanamycin. This gene was isolated from the resistant bacterial strain and copied into other plasmids. Through the use of enzymes, scientists can design plasmids that incorporate resistances against selection agents such as kanamycin.

Kanamycin is an antibiotic that kills certain species of bacteria.
Kanamycin is an antibiotic that kills certain species of bacteria.

There are many pathways through which resistance to aminoglycosides, such as kanamycin, take effect. Genetic resistance to kanamycin can be a result of decreased cell permeability or cellular inactivation of the kanamycin enzyme. It's also possible for a cell to exhibit resistance to kanamycin by a chromosomal change leading to an alteration of that cell's ribosomes. This last resistance, however, isn't as useful for geneticists as the other pathways, because it relies on chromosomal DNA and not designed plasmids. In other words, this resistance is a naturally occurring one and can't be inserted.

The kanamycin resistance gene has some resistance crossover to other antibiotics and selection agents such as gentamycin and neomycin. This trait makes the kanamycin resistance gene less useful because broad selection agents prevent specific selection of bacterial strains. In other words, if a scientist wanted to study the interaction of two plasmids, inserting them both into a single-celled organism such as yeast, the scientist couldn't use neomycin or gentamycin resistance as a selection marker if kanamycin resistance is already being relied upon.

Kanamycin resistance typically is used in laboratories, and it has become a common selection agent for use in genetically modified organisms. As one of the most common antibiotics, kanamycin is assumed to exist in abundance. Consequently, there are few restrictions on the use of kanamycin in plant transgenics and genetic modifications of plants for large-scale industrial agricultural production.

Taking certain antibiotics may interfere with the effectiveness of birth control pills.
Taking certain antibiotics may interfere with the effectiveness of birth control pills.

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Discussion Comments


In many plasmid vectors, only Kan-resistance is listed. Do they have the same DNA sequence in all these different vectors? Is the DNA sequence for the resistance in these vectors the same as NPTII that is also resistant to Kanamycin when selecting transgenic plants? Thanks!


Nearly all of the antibiotics scientist use in labs (ampicillin, kanamycin, Chloramphenicol) are not used in the clinics anymore. Most bugs out there developed this resistance on their own (it's quite easy for them to do so) during the initial uses of these antibiotics decades ago. In short, you have nothing to worry about in terms of this creating superbugs.


I actually read another article about the kanamycin resistance gene awhile ago. From what I understand, it's only slightly possible for a plant with this gene to transfer it to a bacteria. Basically, although it could possible happen, the likelihood is very very slim. So I wouldn't worry about plants that have the kanamycin resistance gene at all.


@KaBoom - I can understand your fears, but I'm sure scientists have this under control. I don't think the kanamycin resistance gene would be used for studies so much if it was that dangerous. I know people sometimes get a little wacky about genetic modification, but I don't think there's really anything to worry about.

I'm personally disturbed by the fact that this gene developed on its own though. I too worry about superbugs, so it's pretty disheartening to hear about a bacteria (any bacteria) developing antibiotic resistance.


This is interesting, but it sounds kind of dangerous to me. Why in the world would we want to introduce a gene that confers antibiotic resistance to any kind bacteria? Don't we already have enough superbugs out there? I suppose it's OK to do it in plants, but definitely not bacteria. It would be too easy for this gene to spread to other types of potentially harmful bacteria.

I know scientific study is important, but I don't think it should be done at the expense of public safety. I'm sure scientists could find a different kind of genetic market to track and use in their experiments.

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