E. Coli & Genetic Engineering
E. coli bacterium is a common inhabitant of the human intestine. It also lives in the intestine of many other animals, wild & domestic. It is one of the most thoroughly studied of all living things. It is a favorite organism for genetic engineering as cultures of it can be made to produce unlimited quantities of the product of an introduced gene. Several important drugs (like insulin) are now manufactured in E. coli.
What makes a friendly bacteria like Escherichia coli turn pathogenic? It picks up new traits through mutation of its own genes or by acquiring genes from other organisms. Artificial genetic engineering involves rampant DNA recombination and transfer of genes across divergent species barriers.
E.coli O157:H7, the deadly E. coli on the nightly news, is an E. coli that has acquired new genes that increase its virulence (toxicity) from another microbe. When a microbe dies some of its genetic material may survive to be taken up by another microbe [thus, why you can still get sick from the "inactivated" virus in vaccines]. The uptake of external DNA is called transformation. The transfer of genes from one species of bacteria to another is called horizontal transfer of genes (as opposed to the vertical transfer of genes through heredity).
E.coli O157:H7 acquired several new genes for virulence factors-the most important is the Shiga-like toxin called Vero toxin. Vero toxin is a small protein that acts to cleave the host cell's rRNA (ribosomal RNA) and hence disrupt protein biosynthesis by ribosomes. Ribosomes are the sites where the cell assembles proteins according to genetic instructions.
The Shiga toxins are from Shigella dysenteriae, the causative agent of epidemic dysentery (bloody diarrhea). The deadly E.coli picked up the gene for Vero toxin from a bacteriophage (a virus that infects bacteria) that presumably had previously infected Shigella. the deadly E.coli has also acquired new hemolysins that kill red blood cells by forming pores in their membranes (essentially dissolving them).
E.coli O157:H7 causes enterohemorrhagic disease. Many bacteria produce toxic proteins called enterotoxins (Cholera, pertussis). This E.coli strain has new adhesins that attach better to intestinal cells. Epithelial (border) cells in the intestines and blood vessels are killed and hemorrhaging occurs. This causes a loss of fluid from the circulatory system (hypovolumia)… eventually there is kidney failure, shock, and death.
What makes a friendly bacteria like Escherichia coli turn pathogenic? It picks up new traits through mutation of its own genes or by acquiring genes from other organisms. Artificial genetic engineering involves rampant DNA recombination and transfer of genes across divergent species barriers.
E.coli O157:H7, the deadly E. coli on the nightly news, is an E. coli that has acquired new genes that increase its virulence (toxicity) from another microbe. When a microbe dies some of its genetic material may survive to be taken up by another microbe [thus, why you can still get sick from the "inactivated" virus in vaccines]. The uptake of external DNA is called transformation. The transfer of genes from one species of bacteria to another is called horizontal transfer of genes (as opposed to the vertical transfer of genes through heredity).
E.coli O157:H7 acquired several new genes for virulence factors-the most important is the Shiga-like toxin called Vero toxin. Vero toxin is a small protein that acts to cleave the host cell's rRNA (ribosomal RNA) and hence disrupt protein biosynthesis by ribosomes. Ribosomes are the sites where the cell assembles proteins according to genetic instructions.
The Shiga toxins are from Shigella dysenteriae, the causative agent of epidemic dysentery (bloody diarrhea). The deadly E.coli picked up the gene for Vero toxin from a bacteriophage (a virus that infects bacteria) that presumably had previously infected Shigella. the deadly E.coli has also acquired new hemolysins that kill red blood cells by forming pores in their membranes (essentially dissolving them).
E.coli O157:H7 causes enterohemorrhagic disease. Many bacteria produce toxic proteins called enterotoxins (Cholera, pertussis). This E.coli strain has new adhesins that attach better to intestinal cells. Epithelial (border) cells in the intestines and blood vessels are killed and hemorrhaging occurs. This causes a loss of fluid from the circulatory system (hypovolumia)… eventually there is kidney failure, shock, and death.