Bacteria and Viruses — Scientific Principles

Scientific Principles

Bacterial cells lack a membrane-bound nucleus but still possess genetic material and cellular machinery. Prokaryotic does not mean structureless. Their metabolic diversity includes organisms involved in decomposition and nutrient transformations. Cyanobacteria are photosynthetic bacteria, illustrating why bacteria should not be defined solely as pathogens or organisms unable to make organic matter.

Viruses are not cells. Their genetic material may be DNA or RNA, depending on the virus, enclosed in a protein coat. Replication depends on suitable host-cell machinery. A bacteriophage infects bacteria; the name does not mean that it is itself a bacterium. The host range and the nature of the infectious entity must be kept separate.

An antibiotic acts on susceptible bacterial targets. An antiviral addresses a viral infection through a different mechanism. Choosing a medicine therefore requires identifying the relevant illness and professional assessment; these distinctions are not instructions to self-diagnose or select treatment. A bacterial complication can coexist with a viral illness, which is different from saying that an antibiotic kills the virus.

Antimicrobial resistance concerns microorganisms becoming less susceptible to medicines intended to act against them. Selection can favour resistant variants when susceptible organisms are removed. Misuse and overuse are important pressures, but exposure does not mean that a patient's body has become the resistant organism. WHO distinguishes antibiotic resistance within the broader category of resistance involving bacteria, viruses, fungi and parasites.