PBCV-1 negativley stained with uranyl acetate (photograph kindley provided by Roger Hendrix). The smaller particles are lambda phage. Note that (i) long fibres are associated with the particles (small arrow), (ii) a distinctive 20- to 25-nm spike structure (large arrow) extends from one vertex of the particle, (iii) the particle appears to be packed asymmetrically, and (iv) an interior membrane appears to be located inside the capsid which extends to the unique vertex.