A team of researchers has figured out that that certain bacteria can tell the difference between light and dark, and become ten times more virulent when exposed to sunlight…

This not a really new story, but i think it might interest you.

This is the first time light has been shown to change the course of a bacterial disease. And these particular bacteria are probably not alone: As many as one-third of other bacterial species may react to light by producing physiological or chemical changes.Brucella, the bacteria that cause the infectious disease brucellosis, and more than 100 other kinds of bacteria contain proteins originally thought to be functional only in plants, according to Winslow Briggs, one of the researchers and director emeritus of the Carnegie Institution Department of Plant Biology. “Many of these bacteria have been pretty well studied, but nobody has ever showed light responses in them,” said Trevor Swartz, the study’s lead author and a former postdoctoral fellow in Briggs’ lab. “In Brucella, we showed that light actually is controlling infection.”…The researchers were originally stumped by the appearance of light-sensitive proteins in bacteria, organisms not previously thought to care about light or dark. “The question was, what the blazes is it doing in Brucella?” Briggs said. “That’s where we had to hook up with people who were handling Brucella, because it’s a very dangerous pathogen.”

The proteins that signal to the bacterium that it is in the presence of light appear to do so in order to indicate if the bacterium is inside or outside of the host. If outside the host, the bacteria should act one way (more virulently), if inside the host, they can be more laid back.This was published in Science, and you can read the press report here.The molecule in question is a set of proteins with a “flavin-binding LOV domain.” These molecules are found widely in plant tissues, fungi, and bacteria (algal phototropins). The molecules react to light and produce a signal that outputs to a wide range of systems. This means that these molecules can react to light and then originate a cascade of reactions elsewhere in the cell.The reason that this research is interesting is this: It was already understood that flavin binding LOV domains were involved in reactions to light in plants as well as bacteria that used light, but not understood what they were doing in other bacteria.This left open two possibilities, predicted by evolutionary theory. One is that there is a light-related function that was as yet not understood, the other being an unknown function that had nothing to do with light. The first prediction is obviously the more interesting adaptationist perspective.From the Perspectives report in Science by Kennis and Crosson:

Swartz et al. show that light increases the enzymatic (autophosphorylation) activity of a Brucella LOV histidine kinase (see the figure). Strikingly, they demonstrate that visible light increases the virulence of B. abortus in a macrophage infection model: Wild-type Brucella is 10 times more virulent after exposure to visible light than bacteria that were never exposed to light. Deletion of the gene encoding LOV kinase from Brucella abolished this light-mediated virulence response, reducing bacterial proliferation in light-exposed macrophage cells to the level observed in the dark.

The next step? Well, light can be a two-edged sword. It seem based on this research to increase virulence, but it also can be deadly to bacteria. So there must be some interesting trade offs going on. What is the molecular evolutionary response to this conundrum?______________-KENNIS, J. T. M. & CROSSON, S. (2007): Microbiology. A bacterial pathogen sees the light.. Science, 317, 1041-2.SWARTZ, T. E., TSENG, T., FREDERICKSON, M. A., PARIS, G., COMERCI, D. J., RAJASHEKARA, G., KIM, J., MUDGETT, M. B., SPLITTER, G. A., UGALDE, R. A., GOLDBAUM, F. A., BRIGGS, W. R. & BOGOMOLNI, R.A. (2007): Blue-light-activated histidine kinases: two-component sensors in bacteria.. Science, 317, 1090-3.

Have you read the breakthrough novel of the year? When you are done with that, try:

In Search of Sungudogo by Greg Laden, now in Kindle or Paperback
*Please note:
Links to books and other items on this page and elsewhere on Greg Ladens' blog may send you to Amazon, where I am a registered affiliate. As an Amazon Associate I earn from qualifying purchases, which helps to fund this site.