Bacteria are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, …

Viruses differ from bacteria in several important ways. Viruses are not living organisms; they can only replicate in the cells of a host. By contrast, bacteria are single-celled organisms that can reproduce …

For example, “ Clostridium botulinum ” is the scientific name for the bacterium that causes botulism. Within a species, scientists may discover different types, or strains, of a bacterium.

Nov 7, 2025 · Each bacterium grows and divides independently of any other bacterium, although aggregates of bacteria, sometimes containing members of different species, are frequently found.

Aug 8, 2025 · In 1838, the German naturalist Christian Gottfried Ehrenberg called them ‘bacteria’, from the Greek word ‘baktḗria’, meaning ‘little stick’. Later, Robert Koch’s research, famously dubbed …

Apr 18, 2025 · What Exactly is a Bacterium? At the most basic level, a bacterium is a single-celled organism without a nucleus. This classifies it as a prokaryote, meaning its genetic material floats …

Bacteria are single-celled microorganisms that differ from all other organisms (the eukaryotes) in lacking a true nucleus and organelles such as mitochondria, chloroplasts, and lysosomes.