Research with bacteriophages (phages) has opened up promising perspectives for their use as antimicrobials for controlling plant, animal, and human diseases, being of special interest in an era of rising antibiotic resistance. Understanding how a phage recognizes a bacterial cell and begins the infection process is important for addressing some major challenges for these applications, particularly in relation to resistance development and spectrum of activity. To investigate the initial event of host recognition, the structural interaction of a phage binding to its receptor will be studied in this project. ¦Xacm4-11 is a short-tailed, icosahedral-headed, double-stranded DNA phage of the Podoviridae family that is specific to the type IV twitching motility pilus of the phytopathogenic bacterium Xanthomonas citri pv. citri. This phage forms in vitro a stable complex binding by its tail to pili isolated from X. citri cultures that can be co-precipitated and observed by transmission electron microscopy. For single particle analysis by cryoelectron microscopy (cryo-EM), the phage tail will be chemically separated to avoid the relatively large size of the capsid interfering with the alignment of the particles. A symmetric reconstruction will be performed for the isolated tails while the pili will be separately helically reconstructed. Then, it will be possible to fit these higher resolution cryo-EM reconstructions into a lower resolution asymmetric reconstruction of the tail-pilus complex. This final assembly could reveal unprecedented details of the molecular basis for the adsorption of a podovirus to a pilus receptor, providing insights into how these bacteria killers home in on their targets.
News published in Agência FAPESP Newsletter about the scholarship: