Vibrio cholerae, bacteriophages and the anti-phage system PLE. Image credit: Stephanie G Hays (CC BY 4.0)
Bacteriophages, or phages for short, are viruses that infect bacteria, take over the molecular machinery inside the bacterial cells and use it to make more copies of themselves. The bacteriophages then break open, or “lyse”, the bacterial cell, releasing the viral copies into the environment, ready to infect more bacteria nearby.
Hays and Seed set out to understand how the timing of lysis can impact the bacteriophage, using the bacterium Vibrio cholerae – which causes cholera – and its bacteriophage called ICP1. This analysis revealed that the ICP1 phage uses a gene called teaA as the first step in the lysis of bacterial cells. The ICP1 phage can also delay that lysis with a second gene called arrA. This “lysis inhibition” gives the bacteriophages more time to make copies of themselves inside the bacterium, so even more are released when the cell finally breaks open.
Hays and Seed also found that the Vibrio cholerae cells can defend themselves against lysis inhibition using a single gene called lidI. This gene is part of a system that defends against bacteriophage attack called the PLE, which consists of several genes of previously unknown function. Hays and Seed saw that the lidI gene disrupts lysis inhibition, speeding up the bursting of infected bacterial cells, which in turn decreases the number of bacteriophages produced from each infected cell.
Lysis inhibition had previously only been observed in the bacterium Escherichia coli. Now that researchers know that ICP1 bacteriophages also delay lysis in Vibrio cholerae, this might lead to more studies exploring this process in samples from cholera patients. Further studies could test to see if the phenomenon of lysis inhibition may also exist in yet more bacterial species.
