February 19, 2004

Seeing Red

One of the most delightful aspects of microbiology is the preponderance of pretty colors to be found in labs, both due to experimental reagents (like indicator dyes in plates) and, occasionally, the organisms themselves**. For example, Serratia marcescens is a gram-negative bacteria that appears red at room temperature. This helpful visual property of S. marcescens has brought it notoriety in at least two "cases" that I can think of.

First off, it's claimed that in 1950, the US Navy used S. marcescens in an attempt to determine the vulnerability of San Francisco (used as a model port city) to a biological warfare. Aerosolized S. marcescens (accounts, none of which seem reliable, vary as to whether a large balloon or hoses were used) was released in the harbor, with the intent that the spread of the bacteria would be monitored. S. marcescens was thought to be an ideal species to use in this experiment because it was easily identifiable (due to its color) and nonpathogenic.

It wasn't actually nonpathogenic. Oops. Apparently there were unusually high incidences of pneumonia and bladder infections in San Francisco following the experiment.

A more charming anecdote about S. marcescens concerns the feast of Corpus Christi. A legend holds that a priest celebrating Mass at Bolsena found, in breaking the host at Communion, that the wafer had blood on it (a more literal case of transubstantiaton that one normally hopes for). The "miracle of Bolsena" was supposed to have been the impetus for Pope Urban IV's proclamation of the bull Transiturus, which established the feast of Corpus Christi (the body of Christ). Some microbiologists like to claim that the most likely explanation for the red Communion host was contamination by S. marcescens. Unfortunately, history doesn't support either the miracle of Bolsena or the microbiological speculation. It's still a fun story, though.

**I should point out that pretty colors are not the sole provenance of microbiologists. Continue reading for (pretty) proof.

Using especially fancy immunofluorescence, Dr. Conly Rieder of the New York State Department of Health's Wadsworth Center has created unbelievable images to study the movement of chromosomes during the cell cycle. This is a picture of a newt lung cell that is arrested in metaphase. Note how all of the chromosomes are lined up on the metaphase plate aside from the wayward one that has migrated to the right-hand spindle pole--this is why the cell is arrested.

Rieder Image

Chromosomes are in blue, microtubules are in green.

Posted by Susan at February 19, 2004 05:30 PM

I'm not sure I understand how the Navy could have tracked the microorganism visually. Do they propagate in clusters large enough so that the red color is apparent wherever the bacteria is? It seems like you'd need a significant concentration of bacteria for the color to be visible.

Additionally, the Navy would have to have been able to convince the entire population of San Francisco not to wash the red stains off their clothes for the duration of the experiment.

Also, that picture is awesome.

Posted by: Ray at February 20, 2004 05:22 PM

I think the idea was that they would collect samples in the outlying area and look for the bacteria there; it would take a ridiculous concentration of S. marcecens to have them competing out the normal microbiotic population of the city.

And yeah, the picture rules.

Posted by: susan at February 22, 2004 08:53 PM

Transubstantiation.................also a word which describes the act whereby every single thought by every single person is 'recorded' on not the brain, but, the original substance from which everything..............EVERYTHING in the cosmos originates from................

Posted by: Michael at March 26, 2004 05:29 PM
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