Attack and defence in the microverse
A research team of the Cluster of Excellence “Balance of the Microverse” at the University of Jena, is shedding light on the regulatory mechanisms of small RNA molecules—which play a decisive role in viral infections of bacteria.
Viruses need hosts. Whether it’s measles, the flu or coronavirus, viral pathogens cannot multiply or infect other organisms without the assistance of their hosts’ cellular infrastructure. However, humans are not the only ones affected by viruses: animals, plants and even microorganisms can all serve as hosts. Viruses that use bacteria as host cells are called bacteriophages (or simply “phages” for short) and are thought to be the most abundant biological entities of all. Just as the human immune system springs into action to resist a flu or coronavirus infection, bacteria do not simply allow phages to infiltrate their cellular machinery without a fight.
A research team at the University of Jena and its Cluster of Excellence “Balance of the Microverse” has examined in detail the complex interaction of attack and defence strategies when cholera-causing bacteria (Vibrio cholerae) are infected with a bacteriophage known as VP882—and discovered that tiny RNA molecules play a decisive role. The researchers’ findings have been published in the latest issue of a prestigious journal, Cell Host & Microbe.
From harmless housemate to cunning kidnapper
There are two ways in which phages can multiply after infecting bacteria: either as invisible passengers, hidden in the bacteria’s genetic material, or as cunning kidnappers, multiplying in vast numbers in bacterial cells without regard for potential losses and, ultimately, destroying the cells. Which method a phage adopts depends on whether sufficient numbers of other host cells are available in the immediate environment to provide shelter.
But how do phages determine this? “They rely on a chemical counting mechanism that bacteria use to identify other members of their species,” explains Prof. Dr Kai Papenfort of the University of Jena, who headed up the project. Known as “quorum sensing”, this method uses signal molecules that are produced by bacteria and released into their surroundings. At the same time, the bacteria monitor the concentration of these molecules using specific receptors, thereby gaining information about the size of their current population. “The phages’ trick essentially involves ‘listening in’ to this chemical communication between bacteria,” says Papenfort.
In their experiments, the Jena researchers examined what happens to the phages and bacteria once the bacteria emit their quorum sensing signals. “We have observed that 99% of bacteria are destroyed within 60 minutes,
