This open access work looks like a solid way to measure accumulated biochemical damage in nematode worms, and link it to both its causes and its resulting effects on life span: "A common property of aging in all animals is that chronologically and genetically identical individuals age at different rates. To unveil mechanisms that influence aging variability, we identified markers of remaining lifespan for Caenorhabditis elegans. In transgenic lines, we expressed fluorescent reporter constructs from promoters of C. elegans genes whose expression change with age. The expression levels of aging markers in individual worms from a young synchronous population correlated with their remaining lifespan. We identified eight aging markers, with the superoxide dismutase gene sod-3 expression being the best single predictor of remaining lifespan. Correlation with remaining lifespan became stronger if expression from two aging markers was monitored simultaneously, accounting for up to 49% of the variation in individual lifespan. ... Our results indicate that pathogenicity from Escherichia coli used as food is a major source of lifespan variability due to variable activation of the insulin-signaling pathway. ... E. coli, the common diet for worms, is mildly pathogenic whereas Bacillus subtilis is not pathogenic. Accordingly, worms fed B. subtilis live longer than worms grown on E. coli. ... The finding that the amount of sod-3 expression present in a middle-aged worm is correlated with its remaining lifespan indicates that events have occurred that affect its future aging trajectory. If so, feeding a worm either E. coli or B. subtilis should have greatest effect when it is young rather than when it is old. To test this, we fed worms one type of bacteria (E. coli or B. subtilis) when they were young and then shifted them to the other type of bacteria at day 8 of adulthood. Young worms fed E. coli had short lifespans, no matter what they ate when they were old. Conversely, young worms fed B. subtilis had long lifespans no matter what they ate when they were old. This result indicates that pathogenicity or some other factor associated with E. coli initiates changes in young worms that affect their time of death later on."