What is the difference between a bacterium and a virus?

Question

Someone recently asked in class why antibiotics don’t work on viruses, and that sparked a whole discussion. I looked it up and found a clear breakdown of how bacteria and viruses are completely different, not just in size but also in structure, reproduction, and how they interact with hosts. Here’s everything I found, summarized and compared side by side.

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Aino 2025-06-13T18:30:19+00:00 1 Answer 5 views
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Answer ( 1 )

  1. fleming
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    2025-07-13T14:46:12+00:00
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    Size and structure

    • Bacteria are living cells with cytoplasm, ribosomes and a plasma membrane, usually 0.5‑5 μm.
    • Viruses are much smaller (20‑300 nm) and consist only of nucleic acid plus a protein coat, sometimes an envelope. They have no cytoplasm or ribosomes.

    Metabolism

    Bacteria make their own ATP and proteins. A virus aint got any metabolic machinery; outside a host cell it is basically inert.

    Reproduction

    Bacteria divide by binary fission on suitable media. Viruses must enter a host cell and hijack its machinery, then assemble from parts rather than split in two.

    Genetic material

    Bacteria always carry double‑stranded DNA (often circular) plus maybe plasmids. Viruses can have DNA or RNA, single‑ or double‑stranded, linear, circular or segmented.

    Treatment

    Antibiotics target bacterial cell wall, ribosome or DNA gyrase, so they do nothing to viruses. Antivirals are designed to block viral enzymes or entry steps and are usually narrow spectrum.

    Examples

    Bacterium – Escherichia coli, Staphylococcus aureus. Virus – Influenza A, SARS‑CoV‑2.

    Bottom line

    Bacteria are independent single‑celled organisms. Viruses are obligate intracellular parasites, basically genetic material in a protein package.

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