Viruses cause bacteria to produce pink pigments

Cyanobacteria (also known as blue-green algae) and other oceanic bacteria are able to convert carbon dioxide and water into carbohydrates and oxygen with the help of sunlight, just like plants. "They use light-harvesting complexes in order to capture the energy from the light," says microbiology Professor Nicole Frankenberg-Dinkel from the University of Kaiserslautern. "These consist of proteins and color pigments." The latter are also responsible for the characteristic coloration. In the case of plants, for example, this is the green pigment 'chlorophyll', in cyanobacteria this is the blue pigment 'phycocyanobilin' and the pink pigment 'phycoerythrobilin'.

"The synthesis of these pigments is already well understood," the microbiologist adds. "So far researchers have only been able to demonstrate their presence in organisms which release oxygen through the process of photosynthesis." In addition to this form of conventional photosynthesis performed by plants and cyanobacteria, there are also other variants that do not release any oxygen.

The biologists at Kaiserslautern sought to investigate, together with their Israeli research colleague and bioinformatician Oded Béjà (from the Technion-Israel Institute of Technology), the extent to which pigment synthesis is prevalent in certain marine regions. The biosynthesis of pink pigment 'phycoerythrobilin' was the focus of their work. "The genetic information for the synthesis of the pink pigment is widespread throughout all the world's oceans," says the professor. This is where the researchers made a notable discovery: this information is wide spread in viruses. "The viruses carry genetic information which can be used to produce the pink-colored pigments," Frankenberg-Dinkel explains. The viruses introduce this genetic information into bacterial cells which enable them to synthesise the pink pigment. "What is new is that we are able to use bioinformatic analyses to determine the type of viruses which carry this genetic information," Frankenberg-Dinkel continues. "We were able to show that the viruses most likely affect those microbes for which we do not yet know what purpose the pigment serves."

For her study, Frankenberg-Dinkel and her team analysed datasets obtained from metagenome databases. "These contain all the genetic information of all the organisms we would usually extract during a field trip at sea, for example," the researcher explains. "This technique allows us to gain a detailed insight into the ecosystem without having to investigate it on location."