Fig 4. Histograms of body lengths, B (μm, left), and swimming speeds, U (μm s⁻¹, right), for rod-shaped bacteria (excluding spirochaetes and Spiroplasma) (〈B〉 = 5.79 ± 9.33 μm (n = 66), 〈U〉 = 48.33 ± 98.47 μm s⁻¹ (n = 77)), spirochaetes (〈B〉 = 18.59 ± 13.02 μm (n = 17), 〈U〉 = 17.94 ± 18.84 μm s⁻¹ (n = 15)), Spiroplasma (〈B〉 = 5.72 ± 0.28 μm (n = 2), 〈U〉 = 1.69 ± 0.81 μm s⁻¹ (n = 2)) and archaea (〈B〉 = 2.71 ± 2.12 μm (n = 10), 〈U〉 = 89.18 ± 126.57 μm s⁻¹ (n = 10)) from our database.

Most organisms have sizes below 10 μm (〈B〉 = 7.75 ± 10.85 μm (n = 95)) and swimming speeds below 100 μm s⁻¹ (〈U〉 = 46.98 ± 95.42 μm s⁻¹ (n = 104)).