TABLE 3.
Surface-to-volume ratios of bacteria of different sizes and shapes
| Organism | Diam (μm) | Length (μm) | Surface area (μm2)a | Vol (μm3)a | Surface/vol ratio (μm2/μm3) | Pu ratiob |
|---|---|---|---|---|---|---|
| P. ubique | 0.2 | 0.5 | 0.31 | 0.014 | 22 | 1 |
| Cocci | 1 | 3.14 | 0.52 | 6 | 3.7 | |
| 2 | 12.56 | 4.2 | 3 | 7.3 | ||
| 3 | 28.26 | 14.13 | 2 | 11 | ||
| Rods | ||||||
| E. coli | 1 | 2 | 6.28 | 1.3 | 4.8 | 4.6 |
| 1 | 8 | 25.12 | 6.02 | 4.2 | 5.3 | |
| E. fishelsoni | 40 | 250 | 31,400 | 3 × 105 | 0.10 | 220 |
| 80 | 600 | 151,000 | 3 × 106 | 0.05 | 440 |
a
Calculations for symmetrical, spherical cocci: surface area = 4πr2; volume = 1.33πr3. Calculations for rods, assumed to be capped by two equal and symmetrical hemispherical ends: surface area = 4πr2 + 2πrl; volume = 1.33πr3 + πr2l.
b
The “Pu ratio” is a multiplication factor that describes how much more volume one unit of cell surface area must support compared to the same unit of surface area in P. ubique.