E. coli BacteriumIs The Cornerstone of Modern Biology

Shin

But “we are still in the process of truly knowing the potential of E. coli,” biologists say.

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In 1885, the renowned German-Austrian professor of pediatrics, Theodor Escherich, found a novel bacterium in the feces of healthy people. He named it Bacterium coli commune because it’s from the colon.

Scientists said that the naming was oversimplistic. So they renamed it as Escherichia coil in 1919 in honor of Professor Escherich who died in 1911 — and who discovered the bacterium that made modern biology possible.

“Important findings and Nobel Prizes in biology have been developed in E. coli,” say modern biologists.

What is Escherichia coli Really?

E. coli is a member of the gut microbiota. Despite that it constitutes <1%, it’s one of the earliest microbes to colonize the gut of infants. E. coli consumes oxygen in the gut, promoting an oxygen-deprived environment for other gut microbes to thrive. Yes, the vast majority of gut microbes hate oxygen.

But E. coli can be a double-edged sword in the gut. At times it can cause food poisoning and diarrhea, urinary and respiratory tract infections, or even contribute to chronic gut inflammation, Crohn’s disease, and colorectal cancer. All of these depend on what type of E. coli strains that are growing inside the body.

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Cracking the Genetic Code

E. coli is a “model organism” in molecular biology. With only about 4000 genes, E. coli has a simple genome ideal for experimenting. By tweaking, changing, adding, or deleting a nucleotide in the E. coli genome and then see what it does, scientists can understand how genetics works.

Textbook facts of how a cell reads genes and performs instructions encoded in the genes — like DNA replication and protein synthesis — and more advanced genetics like how genes are regulated and mutated were all also understood from the E. coli genome. Researchers decoded genetics from E. coli.

Probing Evolution

E. coli has demonstrated that random mutations can occur — which underpin variation and natural selection of the Darwinian theory of evolution.

Variation means that they're different traits in the population. Natural selection means that certain environmental conditions prefer (or selects for) a certain trait. Thus, organisms that develop a unique trait (via random mutation) that enable them to better survive in the environment will pass on the trait to the next generations. This is evolution, in general.

Experimental evolution is when scientists create an environment that mimics nature’s evolution in the lab. With this, they showed that E. coli can mutate (via random mutations) to adapt to harsh conditions — by evolving resistance to antimicrobials, lethal virus infection, or high-oxygen environments.

E. coli demonstrated the Darwinian theory of evolution.

The latest and perhaps the most remarkable feat in experimental evolution is that E. coli can evolve plant-like abilities to consume carbon dioxide for energy: Scientists Evolved a Bacterium to Be More Like Plant

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Genetic Engineering & Protein Production

Scientists can insert a new gene into an organism and force that organism to make proteins the gene codes for. These proteins can later be purified and used for other purposes.

This technique is called recombinant protein expression — because the protein is produced from a gene ‘re-combined’ from different organisms. Insulin and human growth hormone are prime examples of this. Other foreign proteins E. coli can make are antimicrobial peptides, therapeutic tryptophan, cancer drugs, etc.

Before using E. coli, scientists collected the pancreas from pigs and cows to save diabetics’ lives.

But recombinant protein expression can be difficult to achieve. Organisms often reject the foreign gene. Even if they accept it, they might degrade the foreign protein the gene encodes. If they don’t degrade the protein, they may not produce it in sufficiently high amounts or in its active form. Or that the foreign protein may kill the organism.

These challenges have been largely solved in E. coli. The simple genome of E. coli enables the easy insertion or removal of genes to modify its physiology in such a way that it can safely make foreign proteins. The fast and scalable growth of E. coli gives a lot of protein yield. And the fact that E. coli is a minimalist in needing a simple environment to grow is another plus.

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Unresolved Potential

Much innovative research to exploit E. coli to its fullest potential is still on-going. And they could potentially be another future cornerstone in molecular biology.

For example, the fatty acid metabolism of E. coli makes it the primary choice of an organism to make renewable biofuels like biodiesel and bioethanol. Scientists have already successfully created an engineered E. coli that makes biofuels. But optimization of the system is still required to improve yield up to commercial and industrial standards.

Another promising utility of engineered E. coli is biosensors to detect hard-to-detect chemicals. “There are several reports where E. coli-based biosensors have been successful for detecting different traits: oxidants, DNA damaging compounds, membrane-damaging compounds, protein-damaging compounds, xenobiotics…,” explain researchers at University of Guanajuato, México, in a 2017 book chapter. But, again, much optimization is still needed to engineer the perfect E. coli for this purpose. “We are still in the process of truly knowing the potential of E. coli.”

This article was originally published in Microbial Instincts.

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