The cell surface receptors that a virus recognizes and binds provides specificity for the organism(s) that it infects. Both lipopolysaccharides and teichoic acids are cell surface proteins of bacteria. Bacteriophages have very diverse mosaic genomes and replicate through both the lytic and lysogenic cycles. Retroviruses are RNA-positive strand viruses, which uses reverse transcriptase to synthesize DNA from an RNA template. Its DNA form of its genome is integrated into the host cell's genome.

A bacteriophage is a virus that infects bacteria. They are not considered living (becuase they cannot replicate on their own) organisms, nor are they techincally considered non-living organisms. They are called obligate intracellular organisms, because they are parasites (kill the cell) that require a host in order to replicate.

Substance X would logically be released in the later part of viral infection. This would be referred to as a "late gene." The reason is that the virus needs time to replicate and assemble its progeny in the host. Lysing the cell immediately after infection would be futile since no progeny could be created. Lytic viruses use the lysis event to escape from the cell, so it cannot occur after viral release. Finally, lytic viruses typically do not integrate into the host chromosome, lysogenic viruses do.