Freethought & Rationalism Archive

Peez · 05-21-2003, 09:48 AM

Here is another example of the medical relevence of evolution. As most of you may know, mitochondria (energy-releasing organelles) found in virtually all eukaryotic cells (animal, fungal, plant, and protist) evolved from symbiotic prokaryotes (bacteria). One of the things that differs between prokaryotes and eukaryotes is their ribosomes (the sites of protein synthesis in all cells): prokaryotic ribosomes are smaller (so-called 70S ribosomes). This presented itself as an ideal target for drugs that are meant to attack bacterial cells without harming our cells (antibiotics), if some could be found that interfered specifically with the function of the 70S ribosomes. Here is a story from Biology of Microorganisms, Fifth Edition, Brock and Madigan 1988 (Prentice-Hall) p. 104:

Quote:

Mitochondria and the Antibiotic Connection

Is it of any practical significance to know that mitochondria are procaryotic in character? Yes: A tragic use of an antibiotic in medicine is linked to the mitochondrion. This antibiotic, chloramphenicol, was widely used in the early days of antibiotic therapy because it was thought to be nontoxic. However, infants and certain other groups turned out to be unusually sensitive to chloramphenicol, and a number of deaths due to blood anemia occurred before the general use of this antibiotic in medicine ceased. What was going on here? We now know that chloramphenicol specifically affects the ribosomes of procaryotic cells, thus inhibiting protein synthesis. In eukaryotes, the ribosomes in the cytoplasm are unaffected by chloramphenicol, but those in the mitochondria, being procaryotic in character, are attacked. Once the connection between chloramphenicol and the procaryotic ribosome was discerned, it made sense that under certain conditions, chloramphenicol might inhibit eukaryotic cells. The cells inhibited in eukaryotes by chloramphenicol are those that are multiplying rapidly, such as blood-forming cells of the bone marrow, where new mitochondria are being synthesized at a rapid rate. With this understanding of the connection between eukaryotic mitochondria and procaryotes, the use of chloramphenicol ceased, except for special cases where it is the only antibiotic that works. Many other antibiotics in clinical use, for example streptomycin, tetracycline, and erythromycin, also interfere specifically with 70S ribosome function, but since these antibiotics are not taken up by eukaryotic cells, mitochondrial ribosomes are unaffected.

I just thought that this might be worth passing on.

Peez

theyeti · 05-21-2003, 11:38 AM

That's cool. Someone needs to write a "evolution and medicine" FAQ. And maybe one for biotechnology as well.

theyeti

Dr.GH · 05-21-2003, 11:41 AM

I think that scigirl is well on the way to this (FAQ).

BioBeing · 05-21-2003, 11:53 AM

Triclosan, the "biocide" fround in many household soaps, mattress pads, cutting boards, toothpastes, toothbrush handles etc etc etc (actually an antibiotic also, with a specific intracellular target) was first patented as a herbicide. Not surprising when you consider the target pathway - fatty acid biosynthesis - is common between plants and bacteria. Hey, it also has antimalarial activity (again, due to the specific target), supporting the view that Plasmodium evolved from plant-like algae.

RufusAtticus · 05-21-2003, 12:16 PM

Quote:

Originally posted by BioBeing
Triclosan, the "biocide" fround in many household soaps, mattress pads, cutting boards, toothpastes, toothbrush handles etc etc etc (actually an antibiotic also, with a specific intracellular target) was first patented as a herbicide. Not surprising when you consider the target pathway - fatty acid biosynthesis - is common between plants and bacteria.

Fatty acid biosynthesis is a eukaryotic feature. What you're probably thinking about here are the prokaryotes Streptomyces, which through horizontal transfer acquired some fatty-acid biosynthesis of eukaryotes and adapted it to make anti-microbial compounds.

Quote:

Hey, it also has antimalarial activity (again, due to the specific target), supporting the view that Plasmodium evolved from plant-like algae.

Not really. Plasmodium has a plasmid that used to be an algae, but now the plasmid only produces fatty-acid synthesis.

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05-21-2003, 11:38 AM	#2
theyeti Veteran Member Join Date: Jun 2001 Location: Denver, CO, USA Posts: 9,747	That's cool. Someone needs to write a "evolution and medicine" FAQ. And maybe one for biotechnology as well. theyeti

05-21-2003, 11:41 AM	#3
Dr.GH Veteran Member Join Date: Jul 2001 Location: Dana Point, Ca, USA Posts: 2,115	I think that scigirl is well on the way to this (FAQ).

05-21-2003, 11:53 AM	#4
BioBeing Veteran Member Join Date: Mar 2003 Location: Memphis, TN Posts: 6,004	Triclosan, the "biocide" fround in many household soaps, mattress pads, cutting boards, toothpastes, toothbrush handles etc etc etc (actually an antibiotic also, with a specific intracellular target) was first patented as a herbicide. Not surprising when you consider the target pathway - fatty acid biosynthesis - is common between plants and bacteria. Hey, it also has antimalarial activity (again, due to the specific target), supporting the view that Plasmodium evolved from plant-like algae.

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