Limits RegistryPUBLIC RECORD
Limits RegistryCandidatus Pelagibacter ubique (SAR11), the most abundant marine bacterium on Earth, has a genome of roughly 1.31 megabase pairs — remarkably streamlined for a free-living organism. This is distinct from smaller genomes found in obligate endosymbionts or parasites (like Nasuia deltocephalinicola), which depend entirely on a host and are not counted as free-living.
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Candidatus Pelagibacter ubique (SAR11), the most abundant marine bacterium on Earth, has a genome of roughly 1.31 megabase pairs — remarkably streamlined for a free-living organism. This is distinct from smaller genomes found in obligate endosymbionts or parasites (like Nasuia deltocephalinicola), which depend entirely on a host and are not counted as free-living.
The smallest known genome, by base-pair count, among bacteria capable of independent (non-obligate-symbiotic, non-obligate-parasitic) life, as sequenced and published in peer-reviewed literature.
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Permanent ID limitsregistry.com/limits/LR-SMALLEST-GENOME-FREE-LIVING-ORGANISM
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Limits Registry. LR-SMALLEST-GENOME-FREE-LIVING-ORGANISM. Smallest genome of a free-living (non-parasitic, non-symbiotic) organism. 2026.