Most specialize in infecting a particular species of bacteria. For the class the host bacterium was Mycobacterium smegmatis, which is related to the bacteria that cause leprosy and tuberculosis, but does not itself cause disease.
Because it is a fast grower, M. smegmatis has become a laboratory workhorse.
About 70 phages that prey on mycobacteria have been previously described. The authors of the PloS ONE paper, who were then freshmen at 12 colleges and universities, reported the isolation, sequencing, and annotation (labeling parts of the genome whose function is known) of 18 new ones.
Angelica and Uncle Howie
The new mycobacteriaphages included two found by the WUSTL students. One, named Angelica, was isolated from soil in Clayton, Mo. The other, called Uncle Howie, was isolated from soil in University City, Mo. Both Clayton and University City are suburbs of St. Louis.
(The students have "naming rights" for the phage they isolate. Consequently, other phage also have amusing names, including Corndog, Fruitloop, Tweety, Predator and Gumball. )
Most of the new phages, including the two St. Louis ones, had what is called siphoviral morphologieslong flexible non-contractile tails, and isometric icosahedral heads.
Once the students had sequenced the phages, they set out to compare their genomes to those of other phages. Bacteriophage genomes are mosaics or assemblages of modules, each of which corresponds to a gene or group of genes.
Since the phages are thought to have evolved by the exchange of these modules, comparing phages can provide clues to their evolutionary history.
The mycobacteriophages seem to fall into nine major clusters, with a few leftovers, or singletons, with no close relatives. Angelica, the Clayton
|Contact: Diana Lutz|
Washington University in St. Louis