Biochemical properties of helicase types are predictive of marine phage infection strategy

• Victoria Barbone, Applied Molecular Biology & Biotechnology, University of Delaware

• Shawn Polson, Depts. of Computer & Information Sciences, Plant & Soil Sciences, Biological Sciences, University of Delaware

Bacteriophages are bacteria-infecting viruses that are extremely abundant, diverse, and important to processes within their environment, though often overlooked in ecological studies. Phage infection cycles can be either lytic—where the phage replicates inside the host cell and lyses it— or lysogenic—where the phage incorporates its DNA into the host’s genome and it can be passed on to subsequent generations. Cell lysis affects nutrient availability and community composition, while DNA insertion moves genes around and affects host biology. The Viral Ecology and Informatics Lab (VEIL) employs replication genes in studying environmental phage populations and the impacts of viral infection on ecosystems, and has identified proteins that are predictive of the infection strategy of marine phages. These replication proteins include polymerases, helicases, and ribonucleotide reductases. DNA polymerase I was found to have mutations that correlated with infection strategy. While DNA polymerase I is responsible for genome replication, it does not work in isolation—therefore helicases are another possible avenue for examining genome to phenome connections. Helicases move along and unwind double-stranded DNA and can be divided into superfamilies based on their biochemical and physical characteristics. The RecB, RecD, and UvsW helicases have been the focus of my project because they were found to have correlation with certain DNA polymerase I mutations. A literature search was conducted to establish their physical properties and unique catalytic residues within known reference sequences, and those catalytic sites were utilized to identify novel sequences from metagenomic data. Using metagenomic sequencing, protein homology and active site validation, and phylogenetic analysis, RecBs, RecDs, and UvsWs were identified in viral populations along environmental gradients and trees were formed to show the relationship with superfamilies, phage sample characteristics, and other replication proteins. This strengthens the framework to predict the impacts of phage infection on microbial systems and ecosystems.