Evolution of bacteria

Evolution of bacteria is the change and diversification of bacterial populations across generations through mutation, natural selection, genetic exchange, and ecological change.

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Horizontal gene transfer: The movement of genetic material between organisms other than by parent-to-offspring inheritance. It lets bacteria acquire genes from distant lineages, rapidly spreading traits such as antibiotic resistance.
Last universal common ancestor: The most recent ancestral population shared by all extant cellular life. It provides a broad evolutionary reference point, though it was not necessarily a single cell.
Phylogenetics: The study of evolutionary relationships among organisms using inherited characteristics and genetic data. It provides the methods used to reconstruct bacterial lineages from comparative evidence.
Antibiotic resistance: The ability of bacteria to survive or grow despite exposure to antibiotics that would normally inhibit them. Resistance demonstrates evolution in action and can spread through selection and gene transfer.
Bacterial species concept: A framework for deciding which bacterial populations count as the same species. Frequent gene exchange and deep genetic variation complicate species boundaries in bacterial evolution.
Natural selection: The differential survival and reproduction of organisms with heritable differences. It changes bacterial populations when variants differ in survival under environmental pressures.
Origin of life: The transition from nonliving chemistry to the first systems capable of biological evolution. Bacterial history begins after life emerged, while its earliest stages remain difficult to reconstruct.
Bacterial taxonomy: The naming and classification of bacteria into groups based on shared characteristics and relationships. Taxonomic names organize bacterial diversity, though classifications change as evolutionary evidence improves.
Antimicrobial stewardship: The coordinated use of antimicrobial drugs to improve treatment while limiting unnecessary exposure. Reducing avoidable selection pressure can slow the evolution and spread of resistance.
Pangenome: The complete set of genes found across the strains assigned to a species or group. It reveals how much bacterial diversity lies outside any single reference genome.