Table 1. Comparisons of estimates and measurements for the smallest bacterium.
| Minimum size estimate | Type of estimate | |
|---|---|---|
| Space limitations from this study | ||
| For a Gram-positive bacterium | 1.02 × 10−20 m3 | Cross-species prediction and theory |
| For bacterium with a minimal membrane | 4.10 × 10−21 m3 | |
| Previous measurements and estimates | ||
| Ground water microbes (Luef et al., 2015) | 4.00 × 10−21 to 1.3 × 10−20 m3 | Measured |
| Mycoplasma pneumoniae (Seybert et al., 2006) | 3.00 × 10−21 to 2.4 × 10−19 m3 | Measured |
| Energetic/growth limitations (Kempes et al., 2012) | 1.45 × 10−20 m3 | Cross-species prediction and theory |
| NRC basic metabolism and components (Knoll et al., 1999) | 4.19 × 10−21 m3 | Calculation of average biochemical properties |
| Size at which individual components would fill the entire cell volume | ||
| Genome scaling | 1.14 × 10−21 m3 (8.66 × 10−22, 1.46 × 10−21)a | |
| Protein scaling | 3.38 × 10−22 m3 (6.90 × 10−23, 6.75 × 10−22) | Cross-species prediction and theory |
| Single membrane scaling | 1.01 × 10−25 m3 | |
| Ribosome scaling | 3.99 × 10−26 m3 (2.03 × 10−28, 1.17 × 10−23) | |
a
The bracketed values, (,), denote the 95% confidence interval.