BACTERIOPHAGE QBETA AS AN EXPERIMENTAL MODEL FOR RNA VIRUS EVOLUTION STUDIES

Abstract

Viral evolution research is a fundamental area within biology that allows us to study the origin and the changes experienced by viruses in response to new environmental conditions. Then, it plays a crucial role in the prediction of viral disease outbreaks, such as the well-known cases of the recent COVID-19 and influenza pandemics. It would not only have practical applications in medicine, but also in astrobiology, when it comes to exploring life in extreme conditions, like the ones found in extraterrestrial environments.

Virus evolution is conditioned by several factors, among which the state of the host stands out. It is known that as the growth phase of the bacteria progresses, their concentration also increases, resulting in a shortage of nutrients and changes in their metabolic state. In the case of the viruses that infect bacteria (bacteriophages), under this condition, virus replication would be affected in case of infection.

In this End of Degree Project, we carried out a study of the molecular adaptation of an RNA bacteriophage, bacteriophage Qß, to its host bacterium (Escherichia coli), when it is approaching the stationary phase, which represents a challenging condition. Starting from an ancestral population, with low heterogeneity and through the system of serial passages, the adaptation of the virus to these bacteria in stationary phase is achieved.

The growth state of the bacteria was found to affect the viral yield, which was lower the closer the bacteria were to stationary phase. Our results also showed that the degree of heterogeneity of the viral population was a decisive factor in its ability to adapt to replicate in stationary phase bacteria. A subsequent genetic analysis of the evolved viruses concluded that the mutations acquired by an evolved population in this unfavourable environment were similar to those obtained under optimal conditions