Viruses and bacteria are fundamentally different entities. A virus consists of a small segment of DNA or RNA encased in a protective shell, while bacteria are complete cells capable of independent life. Key distinctions include that bacteria possess ribosomes, allowing them to synthesize proteins and have their own DNA polymerases for replication. In contrast, viruses rely on the host's cellular machinery for replication and do not have metabolic processes. Bacteria reproduce through methods like fission and budding, while viruses assemble within host cells. Bacterial genetic material is always DNA-based, whereas viruses can have either DNA or RNA as their genetic material. Overall, viruses are considered simpler life forms that depend on hosts for replication and survival.