6.5—Bacteria, viruses, lytic cycle and latency

Bacteria are prokaryotic cells with cytoplasm, ribosomes, a circular chromosome and usually a murein wall. Viruses contain DNA or RNA in a protein capsid and may have an envelope, but no cytoplasm or ribosomes.

A bacterium can carry out its own metabolism and divide. A virus must enter a living cell and redirect host machinery to make viral components, so antibiotics that target bacterial structures do not treat viral infection.

A plasmid can carry a bacterial gene, whereas a virus attaches to a host using surface proteins and releases its genome. Both can cause disease, but their replication mechanisms differ.

Do not call a virus a cell or assume every virus has a lipid envelope. Distinguish structure, replication and treatment.