Invited Speaker Australian Society for Microbiology Annual Scientific Meeting 2023

The crAssphage host specificity puzzle (93483)

Bhavya Nalagampalli Papudeshi 1 , Alejandro A Vega 2 , Cole Souza 2 , Sarah K Giles 1 , Vijini Mallawaarachchi 1 , Michael Roach 1 , Michelle An 2 , Nicole Jacobson 2 , Katelyn McNair 3 , Maria Fernanda Mora 2 , Karina Pastrana 2 , Christopher Leigh 4 , Clarice Cram 1 , Will Plewa 1 , Przemysław Decewicz 5 , Susanna Grigson 1 , George Bouras 6 , Antoni Luque 7 , Lindsay Droit 8 , Scott Handley 8 , Anca M Segall 2 , Elizabeth Dinsdale 1 , Robert Edwards 1
  1. Flinders University, Adelaide, SA, Australia
  2. Biology Department, San Diego State University, San Diego, California, USA
  3. Computational Science Research Center, San Diego State University, San Diego, California, United States
  4. Adelaide Microscopy, University of Adelaide, Adelaide, South Australia, Australia
  5. Department of Environmental Microbiology and Biotechnology, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland
  6. Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, South Australia, Australia
  7. Department of Mathematics and Statistics,, San Diego State University, San Diego, California, USA
  8. Department of Pathology & Immunology, Washington University School of Medicine, St.Louis, Missouri, USA

The human gut is home to trillions of microorganisms, with Bacteroidota being the most prevalent bacteria. These bacteria play a vital role in degrading complex polysaccharides that are difficult for the human body to digest. However, Bacteroides abundance is regulated by bacteriophages (phages) such as crAssphages, which infect and kill them. Despite being one of the most abundant phages in the human microbiome with more than 600 crAssophage species identified computationally, only four crAssphage species have been successfully cultured to date. In this study, we isolated and characterized three novel crAssphage species that infect Bacteroides cellulosilyticus WH2 and isolated them from wastewater. We named the novel species Kehishuvirus winsdale (Bc01), Kolpuevirus frurule (Bc03), and Rudgehvirus redwords (Bc11) which span across three genera which suggest crAssphages may not have co-evolved with their respective bacterial hosts. All three species have podovirus-like morphology and possess a genome size of around 100 kb, consistent with crAssphage characteristics. Genome analysis indicated that while gene order was conserved across the three new species, gene similarity was highly variable.  The discovery of new crAssphage species with podovirus-like morphology and variable gene similarity within taxa has significant implications for understanding the diversity and complexity of phages in the human gut. Only two structural genes encoding a hypothetical protein and a tail spike protein were similar across the three species, which were investigated further for their potential role in bacterial hots specificity. Evolutionary analysis showed tail spike protein to be undergoing purifying selection, and protein interactions suggest this gene plays a role in host specificity by binding to TonB-dependent transporters on the host cell surface. The tail spike protein could be an essential factor in the adaptation of phages to their bacterial hosts, and it could have implications for developing new therapies to target specific bacteria in the gut.