Advances in electron cryo-tomography open up a new avenue to visualize the 3-D internal structure of a single bacterium before and after its infection by bacteriophages in its native environment, without using chemical fixatives, fluorescent dyes or negative stains. Such direct observation reveals the presence of assembly intermediates of the bacteriophage and thus allows us to map out the maturation pathway of the bacteriophage inside its host.
Keywords: 3-D structures; Zernike phase optics; electron cryo-tomography; marine cyanobacterium; phage assembly intermediates; transient biological processes.