Identification and cryoEM Structure Determination of Escherichia Phage YDC107 Tail Found in a Bacteria-Contaminated Buffer

Cryo-electron microscopy data analysis can yield multiple structures from a single heterogeneous dataset. Here, we show a workflow we used for the identification of a contaminant from a cryoEM grid without prior knowledge of protein sequence. We determined the tail structure of Escherichia phage YDC107 from only several thousand particles. The workflow combines high-resolution single-particle data processing with de novo model determination using ML-based methods. Structural analysis revealed that the central part of the phage tail has a C6 symmetry, however the overall symmetry of each segment is C3 due to dimerization of a flexible domain.