A (Annamaria) Mattia, MSc

Soil bacteria and their viruses (bacteriophages or “phages”), are both important components of the soil community. For instance, bacteria play a fundamental role in carbon availability in soil. On the other hand, other bacterial species are deleterious plant pathogens. Given that bacteriophages specifically infect and kill bacteria, interactions between these microorganisms have a pivotal role for  both soil and environmental health. 

However, phages are not mobile units.  Therefore, to colonize new environments and to reach suitable bacterial hosts, they require  alternative sources of movement (e.g. water, soil particles). Mathematical models predict that in absence of movement, phage virulence is reduced as a consequence of phage-bacteria co-evolution dynamics. According to these predictions, “mediocre phage killers” are favoured in order to prevent complete extinction of the available bacterial host source, which would result in the extinction of the bacteriophages themselves.    

Nonethless, more recently experimental studies provided evidence that soil bacteria-feeding (bacterivores) nematodes, can serve as “superhosts” for the phages. In particular, these studies proved that phages are able to utilise nematodes to reach new bacterial hosts. This phenomenon is referred to as “hitchhiking”. In theory, as the selection of “mediocre killers” is not needed to guarantee phage survival, phages’ hitchhiking behaviour might preserve phage virulence.

In light of this, by studying phage-bacteria co-evolution dynamics in presence of superhosts - such as nematodes and insects (Order: Lepidoptera) - this project aims at gaining a deeper understanding of phage-bacteria interactions. Given the importance of such interactions, the resulting output of this research will benefit both soil and environmental health.