Bacteria see the light
Light-activated proteins regulate virulence
Written byCharles Q. Choi
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The researchers also confirmed that LOV histidine kinases were sensitive to light in a plant microbe, a marine microbe and another Brucella pathogen, Brucella melitensis."Brucella has been known about for 120 years, and nobody in the world even suspected that it was sensitive to light," Bogomolni told The Scientist. Further studies will have to determine factors such as the amount of light needed to activate the enzyme, the identity of its downstream partners, and how this mechanism protects the bacteria from macrophages. Bogomolni noted that a similar kind of light-sensitive protein module known as BLUF domains, present in many of the same organisms that contain LOV domains, may also play a role in such a signaling pathway.The researchers suspect that after the bacterium gets ejected from its host - say, when a cow's infected fetus gets aborted and is lying in the field - sunlight helps increase Brucella's virulence using this LOV pathway. This could then make the germ more successful in infecting a new host.The findings "open up a whole new suite of experiments people hadn't even considered before," Emmanuel Liscum at the University of Missouri-Columbia, who did not participate in this study, told The Scientist, noting that most researchers grow bacteria in dark incubators. "I suspect there'll be a huge explosion of data, since performing such experiments concerning dark and light are relatively simple to do."LOV domains are also found in fungi and even in a few Archaea. The protein modules likely evolved in early bacteria and then were co-opted by plants, fungi and other bacteria, Liscum said. Sean Crosson at the University of Chicago, also a coathor on the commentary accompanying the study, noted that LOV histidine kinase may be regulating virulence via numerous pathways. For instance, light-activated HOV histidine kinase could make Brucella more virulent by triggering formation of biofilm, or making the bacterium better at taking up a limiting nutrient, he told The Scientist. While LOV histidine kinase helps Brucella regulate its virulence, "that might not be what it does in other bacteria," Crosson said. "There's a wide range of cellular functions these new photoreceptors could influence. This might be the tip of the iceberg." Charles Q. Choi mail@the-scientist.comLinks within this article:T.E. Swartz et al. "Blue-Light-Activated Histidine Kinases: Two-Component Sensors in Bacteria," Science, August 24, 2007. http://www.sciencemag.orgJohn Kennis http://www.few.vu.nl/~johnJ.T.M. Kennis and S. Crosson, "A Bacterial Pathogen Sees the Light," Science, August 24, 2007. http://www.sciencemag.orgE. Huala et al., "Arabidopsis NPH1: a protein kinase with a putative redox-sensing domain," Science, December 19, 1997. http://www.the-scientist.com/pubmed/9405347G. Gadda, "Flavins: Photochemistry and Photobiology," E. Silva, A.M. Edwards, eds., Royal Society of Chemistry, Cambridge, July 18, 2006. http://www.the-scientist.com/pubmed/17571886Roberto Bogomolni http://www.chemistry.ucsc.edu/faculty/bogomolni.htmlJ.P. Roberts, "Protein Phosphorylation," The Scientist, June 30, 2003. http://www.the-scientist.com/article/display/13894S. Pincock, "Use the force, bacteria," The Scientist, December 1, 2006. http://www.the-scientist.com/article/display/36660/Emmanuel Liscum http://www.biosci.missouri.edu/liscum/LiscumLabPage.html
Sean Crosson http://crescentus.bsd.uchicago.edu
N. Johnston, "Debaffling biofilms," The Scientist, August 2, 2004. http://www.the-scientist.com/article/display/14868
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