The Tsamsa phage – a giant virus isolated from zebras that died of anthrax in the Namibia’s Etosha National Park – could open up new ways to detect, treat or decontaminate Bacillus anthracis and its relatives that cause food poisoning.
Electron microscopy of Tsamsa phage. Scale bar – 100 nm. Image credit: Ganz HH et al.
Bacillus anthracis – the anthrax bacterium – forms spores that survive in soil for long periods. Zebras are infected when they pick up the spores while grazing; the bacteria multiply and when the animal dies, they form spores that return to the soil as the carcass decomposes.
While anthrax is caused by a bacterium that invades and kills its animal host, bacteriophages, literally ‘bacteria eaters’ are viruses that invade and kill bacterial hosts.
The Tsamsa phage is a giant siphovirus belonging to the order Caudovirales. It has a giant, isometric head of 82 nm in diameter, a long, flexible and non-contractile tail of 440 nm and a large genome.
“The first thing the team noticed was that the virus was a voracious predator of the anthrax bacterium,” said Dr Holly Ganz of the University of California, who is the lead author of a paper published in the open-access journal PLoS ONE.
Tsamsa infects not only Bacillus anthracis but also some closely related bacteria, including strains of Bacillus cereus, which can cause food poisoning.
Sequencing the Tsamsa’s genome allowed scientists to identify the gene for lysin, an enzyme that the virus uses to kill bacterial cells, that has potential use as an antibiotic or disinfecting agent.
“With growing concerns about antibiotic resistance and superbugs, people are coming back to look at phages,” Dr Ganz said.
One advantage of bacteriophages is that because they tend to be very specific, they can potentially target only ‘bad’ bacteria while leaving beneficial bacteria unharmed.
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Ganz HH et al. 2014. Novel Giant Siphovirus from Bacillus anthracis Features Unusual Genome Characteristics. PLoS ONE 9 (1): e85972; doi: 10.1371/journal.pone.0085972
