Cell wall peptidoglycan maintains the morphology and cellular integrity of most bacteria. This key component is composed of glycan chains connected by peptide side chains to form a continuous, mesh-like structure that envelops the cytoplasmic membrane. However, little is known about how big molecules, like proteins and DNA, migrate over this essential structure. One technique used by bacteriophages, which are viruses that infect bacteria, is to include a peptidoglycan-hydrolase in their virion to guarantee that their genomic DNA enters the cytoplasm of the host cell. We have recently isolated two new T1-like bacteriophages, YRP1 and CSP2, that appear to have peptidoglycan hydrolases, but other similar bacteriophage, like lambda phage, do not encode peptidoglycan hydrolases.
The biology of lambda phage and its infection of Escherichia coli constitute a well-explored, classic model system in microbiology. The receptor binding protein J at the virion's tail tip is known to engage with the E. coli host's outer membrane protein LamB at the beginning of the infection to attach and release its genomic DNA. The final piece of this puzzle is how it moves DNA through the peptidoglycan layer in the absence of its own peptidoglycan hydrolase.