Table 3 Summary of experimental evidence
From: Repair rather than segregation of damage is the optimal unicellular aging strategy
Organism | Key experimental findings | ||
|---|---|---|---|
Name | Phylogeny | Ecology | |
Cell division by budding facilitating damage segregation | |||
Saccharomyces cerevisiae | Ascomycota | Spoils environment | Limited number of generations of mother cell, sharp increase of generation time of mother cell starting a few generations before death (benign) [26], protein aggregates tethered to organelles that remain in mother cell enabling segregation of unrepaired damage [66] |
Caulobacter crescentus | α-Proteobacteria | Attached to short-lived surfaces | Marked decline of growth rate of mother cell over time (benign) [15],[31],[61] |
Cell division by binary fission | |||
Schizosaccharomyces pombe | Ascomycota | Spoils environment | No apparent decline of growth rate over ≥30 generations (benign), sudden death of mother cell when aggregates accumulate under stress [29] |
Methylobacterium extorquens | α-Proteobacteria (Gram-negative) | Plant leaves, relatively long-lived but seasonal | No decline of growth rate over five generations (benign) [22] |
Escherichia coli | γ-Proteobacteria (Gram-negative) | Grows in relatively long-lived colon, survives outside host | No decline of growth rate over three generations (benign) [22] |
No difference in growth rates between old- and new-pole siblings (benign) [67] | |||
No decline of growth rate (benign) but decline in the presence of streptomycin [27] | |||
Slow decline of growth rate over seven generations in the presence of FPs [16],[17] | |||
No decline of growth rate over approximately 200 generations in microfluidic device in the presence of FPs, but increased probability of sudden death [21] | |||
Stronger aging after mild heat shock or in a repair mutant (chaperone clpB deletion) (in presence of FPs) [33] | |||
Reduced protein aggregate formation if superoxide dismutase overexpressed [57] | |||
Bacillus subtilis | Firmicutes (Gram-positive) | Grows in soil while nutrients present, then sporulates | Similar to E. coli, slow decline of growth rate over four generations under fluorescence microscope [18] |
Mycobacterium spp. | Actinobacteria (Gram-positive) | Pathogen remaining inside host cells for years | Complex growth pattern: alternating polar growth of cell wall, cycling between fast and slow growth, age of pole different from age of sidewall and rest of cell, minimal decline of growth rate with age of sidewall in the presence of FPs [19] |