Scientists have discovered how bacteriophages - viruses that infect bacteria - manage to pierce the bacterial membrane: with an iron spike.
When they crystallized this smaller protein fragment, the x-rays were finally able to resolve its structure, and from this the team had the very first picture of the tip of the spike: a single iron atom held in place by six amino acids, forming a sharp needlelike tip—perfectly suited for piercing the outer membranes of bacteria. The team reports its findings this month in Structure.
Scientists had always assumed that when phages drill their way through the outer membrane, they first have to soften it up a bit in some way, says Mark van Raaij, a biologist and virus expert at the Instituto de Biologia Molecular de Barcelona in Spain, who was not involved in the work. But the discovery of the sharp iron needle, he says, suggests that P2 and F92 don't need any help. "It's like driving a nail or stake through the membrane of the bacteria."