Poliane Alfenas, a professor in the Graduate Program in Agricultural Microbiology, is back in Viçosa after a year at the University of California, Berkeley campus. At the American university, she worked alongside Professor Britt Koskella on different projects involving microbial ecology and evolution, with a special focus on viruses that infect microorganisms. “What struck me about her work is that these are studies involving plants. Most of these studies (on the impact of viruses on microbiomes) are carried out on humans, on the intestinal microbiota, and Professor Koskella works with synthetic microbial communities that she has developed in plants. She manipulates the plant’s microbiome and adds the virus into the equation, to see how viruses influence this dynamic. It matched what we were doing here,” explains Poliane.

The professor says that she traveled to the USA with a series of questions, and returned to Brazil with many answers and, of course, a new wave of questions. “This experience certainly has a big impact. I feel that we are making a leap forward in the type of work we are now doing in the lab,” she says, referring not only to the research objects, but also to the working methods.

Among the advances the professor has made in partnership with the American team is a study on the evolution of the virus’s virulence and its impact on the host bacterium. “We were able to modulate this coevolution of the virus with the bacterium in vitro and with five passages it was already possible to observe an increase in virulence and calculate the adaptive cost of this for the host bacterium. Now, the next step is to try to build a mathematical model to predict the evolution of virulence in other virus-host systems,” she said. “I also worked on determining which resistance and tolerance mechanisms are selected in the host when it is infected by viruses. We had results showing the main responses against viral infection and how the coevolution of virulence and resistance is modulated over time.”

Another line of work was the construction of mutant libraries of bacteria from the Rasltonia solanacearum and R. pseudosolanacearum species. These libraries were used to identify the mechanisms of resistance to different viruses in isolation or combined two by two and to a cocktail containing a mixture of 12 different viruses. “The results were very interesting and promising for the use of the virus cocktail to control the bacterium in the field, since the cost of maintaining resistance to all the viruses was very high for the bacterium.”

The partnership with Professor Britt Koskella continues – two collaborative projects have already been submitted to continue the work and to fund Brazilian students and post-docs. In addition, during this time, Poliane has also established a collaboration with Professor Tiffany Lowe-Power, from UC Davis. One joint project has already been submitted to the NIH and a second, for bilateral collaboration, is being prepared for submission by the end of October.

The work carried out this year in the USA has already resulted in two publications. The first is a review of the importance of the factors that shape the infection and replication of viruses that infect bacteria, and how each influences the range of hosts over evolutionary time. The second is a letter to the editor questioning changes that have been proposed regarding the taxonomy of a bacterium from the Ralstonia solanacearum species complex.