Range: ±0.1 % slower
||Bacteria Escherichia coli
||Stewart EJ, Madden R, Paul G, Taddei F. Aging and death in an organism that reproduces by morphologically symmetric division. PLoS Biol. 2005 Feb3(2):e45. p.0297 right column top paragraphPubMed ID15685293
||"To determine if E. coli experiences aging related to the inheritance of the old pole, [investigators] followed individual exponentially growing cells in an automated fluorescence microscopy system through up to nine generations of growth and reproduction, measuring the physical parameters of each cell over time."
||"The pattern of fast and slow growth rates in this average lineage gives striking evidence for reproductive asymmetry between the progeny cells, as the cells that show a cumulatively slowed rate of growth (shorter lines) are those cells that have more often inherited an old pole during their ancestry. To verify that this pattern in the average lineage is actually due to a difference in growth rate between new and old pole cells, [investigators] performed a pairwise comparison of every set of sister cells that was produced at the eighth generation in each of the films. As sister cells share temporal and spatial surroundings, this comparison controls for potential environmental variation within the microcolony. The comparison (two-tailed t-test) includes cells of all division ages and shows that the average growth rate of the old pole progeny cell is 2.2% (±0.1%) slower than that of the new pole cell. This analysis, performed on 7,953 cell pairs, conclusively demonstrates (p<0.00001, t = 14.40, df= 7952) that the cell that inherits the old pole grows slower than the new pole cell produced in the same division."