E coli K12
As a simple bacteria (prokaryotic cell), E. coli is a model organism for many other prokaryotic organisms.
Let's have a look at why model organisms are useful, and how E. coli K-12 model organism was found!
Model organisms are well-understood organisms that are a simple genetic form and that represent a similar group of organisms that are either of the same complexity, or slightly more complex.The discoveries that scientists make in model organisms can then be hopefully applied to the larger group of organisms without having to do research directly on every organisms, or on the more complex organisms.
So let us take a deeper look at our model E. coli organism and the K-12 strain. A strain is simply a variant or subtype of organism, a bit like how the color navy can be said to be a subtype of the color blue.
You may know E. coli (Escherichia coli) from news articles as a bacteria that can cause food poisoning and illness. But you may not know that there are many strains of E.coli and most types of E. coli are not infectious and some are actually necessary for your digestive system to function. E. coli have evolved over millions of years inside the large intestine of animals such as humans. By colonizing our large intestines, they help us digest food, create vitamins, and produce amino acids for us. One strain of E. coli is a widely used probiotic that helps to reduce bloating in the intestine! This is the E. coli strain DSM 6601 (also known as Nissile 1917), was isolated in 1917 from a World War I soldier who had a resistance to diarrhea, and who was known for having a “strong stomach”. E. coli DSM 6601 has now been used as a probiotic for over 100 years!
But back to our K-12: the E. coli strain K-12 is arguably the single organism about which the most is known. It was first collected by scientists in the early 1900s and it has been used in thousands of labs worldwide and in countless experiments for nearly 100 years!
The K-12 strain was first isolated in 1922 at Stanford University from a stool sample of a patient suffering from diphtheria. Scientists then used the E. coli K-12 in the study of nitrogen metabolism and several biosynthesis pathway experiments. Initially, the K-12 strain still had a dormant viral strand of DNA and still had its gene sequence associated with reproduction in bacteria (its fertility factor). This meant that the bacteria could reproduce in the wild, and possibly get into human or animal guts. Because scientists wanted to use it as their model organism safely and easily, over time, using methods such as UV-radiation and genetic engineering, the viral genome and the fertility factor were removed. This makes it unlikely for the bacteria to survive outside a petri dish and the strain safe enough to work with by beginners at home, school or in labs, as long as you follow safe science procedures.
It is called a biosafety level 1 strain, which means that in North America, you can use it without special permissions. You can learn even more about the E. coli and biosafety in this blog post.
Low-temperature electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bac- terium is oblong shaped. 2005. Photo by Eric Erbe, digital colorization by Christopher Pooley, both of USDA, ARS, EMU., Public domain, via Wikimedia Commons