Researchers from the University of Alaska and the University of Wisconsin have found luminous bacteria in an unlikely location: migrating salmon. They report their findings in the November 2003 issue of the journal Applied and Environmental Microbiology.
The bioluminescent bacterium Photobacterium phosphoreum is almost exclusively found in salt-water environments. In this study the researchers found the bacteria living on the skin of salmon caught in the fresh waters of the Yukon River over 1200 kilometers inland.
"We believe that our P. phosphoreum isolates are of marine origin, forming a saprophytic association with migrating salmon while still in the ocean environment," say the researchers. "When salmon migrate into freshwater luminous bacteria on the salmon are protected by the slime of salmon until the fish are caught."
(Budsberg, K.J., Wimpee, C.F., and Braddock, J.F. 2003. Isolation and identification of Photobacterium phosphoreum from an unexpected niche: Migrating salmon. Applied and Environmental Microbiology, 69: 6938-6942.)
The dark side of good bacteria
Beneficial bacteria in the small intestine may be helping more than just the human host they inhabit. They may also help the bacterium that causes typhoid to invade the cells lining the small intestine, say researchers from Harvard Medical School in the November 2003 issue of the journal Infection and Immunity.
The researchers discovered that some bacteria that are normally found in the small intestine (and serve a beneficial function to the host) produce a compound that causes a specific protein to redistribute on the surface of the cells lining the intestine. This makes the cells more susceptible to infection by Salmonella enterica serovar Typhi, the bacterium that causes typhoid, which uses the protein to attach to and invade cells.
"The commensal microbes which constitute the normal intestinal microflora have previously been shown to have numerous beneficial effects on the health of their human hosts," say the researchers. "The data reported here demonstrate for the first time another mechanism by which commensal microorganisms may influence the health of the human host, by triggering epithelial cell trafficking of a protein that serves as a receptor for pathogenic bacteria."
(Lyczak, J.B. 2003. Commensal bacteria increase invasion of intestinal epithelium by Salmonella enterica serovar Typhi. Infection and Immunity, 71: 6610-6614.)