More than just a pretty face

Posted 15 December 2005 by Tara Smith

Staphylococcus aureus. The name means, literally, "golden grape clusters." Upon staining, these round bacteria are visualized in clumps that resemble bunches of grapes. Every microbiology student is familiar with the most notorious member of the Staphylococcus species, S. aureus, which often produces a distinct yellow pigment when grown on agar plates containing blood. This bacterium itself causes a wide range of illnesses, ranging from food poisoning to deadly skin infections. Of great concern is the fact that strains that resist a number of antibiotics--including methicillin--have been increasingly isolated no only in hospital settings, but also in the community. Vancomycin-resistant strains have also been isolated, but are not yet widespread.

It was recognized almost 25 years ago that the S. aureus yellow pigment consists of a number of carotenoids, similar to those produced in carrots and other fruits and vegetables. Studies of these carotenoid pigments have revealed their free-radical scavenging properties, protecting cells and tissues from the damaging effects of free radicals and singlet oxygen. (In other words, they're antioxidants). Interestingly, one mechanism by which phagocytic cells of the host immune system destroy pathogenic invaders is via release of reactive oxygen species. Do these bacterial carotenoids protect S. aureus against damage initiated by the host immune system? (Continued at Aetiology)

8 Comments

vandalhooch · 15 December 2005

Man, I love this site! I wish Mrs. Smith (or is it doctor?) had posted this about two weeks ago. We were discussing carotenoids as accessory pigments for photosynthesis. This information would have been a pretty cool tangent to discuss with some students.

The Sanity Inspector · 15 December 2005

Forgive the off-topic comment, but the Cobb County GA evolution warning stickers case went before the 11th Circuit Court of Appeals today. I attended the hearing and blogged my observations here: here.

Reed A. Cartwright · 15 December 2005

Cool, Tara.

Tara Smith · 15 December 2005

vandalhooch--

Figures, don't it? I ran across the S. aureus paper this summer, thought it was interesting, then forgot about it. It was only when I re-discovered the previous GBS paper for a book I'm working on that it came back to me.

Sanity Inspector, I expect a post will be forthcoming on that topic from people more familiar with the case than I. Stay tuned...

[ETA: boy, talk about service! Cobb Cty post already up here.

Dean Morrison · 15 December 2005

Not just a pretty face??
-- essential reading for all Dr Tara fans..

six years ago today

Steviepinhead · 16 December 2005

Why it's taken me several days to properly acknowledge Tara's, ahem, cheeky title for this post, I don't know. In recompense, I'll never take Tara's photo--the oft-referenced one in the top right corner of her blog--in vain again! Ah, and an excellent post! Of vague relevance, I heard an NPR report today (still can't deploy this "href" thing successfully, sorry): http://www.npr.org/templates/story/story.php?storyId=5056105. NPR first quoted our, ahem, science-savvy Prez and some public science admin types about the dangers posed by bird flu, all of whom bandied about the "observed" 50% mortality rate. Then they included some quotes from Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, pointing out that this was 50% of the victims identified as seriously ill in the early going, not 50% of the entire population actually exposed to the virus (once they got around to testing those with much more mild symptoms, and those who weren't significantly ill at all, but who were found to have antibodies for bird flu). Also, such a high mortality rate is not at all what would be expected if the virus mutates so as to spread in pandemic fashion from human to human. Why? History, for one thing--the 1918 fly outbreak "only" had a mortality rate of 1 to 2% (which, in a worldwide pandemic, still amounted to a horrific toll of millions of people; no one was suggesting that we take the risk lightly). Dr. Fauci then immediately evoked the E-word: evolution leads us to expect that a highly-contagious virus would not long retain anything like a 50% lethality, because quickly killing off one's host is not the best way for a virus to live long enough to easily spread (a topic we have discussed here on several different threads):

It is highly, highly likely that it will decrease its mortality and its virulence for humans, because from an evolutionary standpoint, it makes no sense for viruses to kill all their hosts. [Emphasis added.]

It would be great if every evolutionary scientist providing media sound bites on "hot" topics did as good a job highlighting the evolutionary implications as succinctly as Dr. Fauci did this morning. Good work!

Dean Morrison · 17 December 2005

Merry Noodlemas!
to all swetcheeks!!!

ambulance nurse · 15 January 2006

I always find stuff to think of here.